Anaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low
blood pressureBlood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
. Common causes include insect bites, foods, and medications.
On a
pathophysiologicPathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...
level, anaphylaxis is due to the release of mediators from certain types of white blood cells triggered either by
immunologicAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
or non-immunologic mechanisms. It is diagnosed based on the presenting symptoms and signs. The primary treatment is injection of
epinephrineEpinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
, with other measures being complementary.
Worldwide 0.05–2% of people are estimated to have anaphylaxis at some point in their life. The term comes from the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words ἀνά ana,
against, and φύλαξις phylaxis,
protection.
Signs and symptoms
Anaphylaxis typically presents with many different symptoms over minutes or hours. The most common areas affected include: skin (80–90%), respiratory (70%), gastrointestinal (30–45%), heart and vasculature (10–45%), and central nervous system (10–15%) with usually two or more being involved.
Symptoms typically include generalized hives, itchiness,
flushingFor a person to flush is to become markedly red in the face and often other areas of the skin, from various physiological conditions. Flushing is generally distinguished, despite a close physiological relation between them, from blushing, which is milder, generally restricted to the face, cheeks or...
, and swelling of the lips, tongue, or throat. Respiratory symptoms may also be present, including shortness of breath, wheezes or
stridorStridor is a high pitched wheezing sound resulting from turbulent air flow in the upper airway. Stridor is a physical sign which is produced by narrow or obstructed airway path. It can be inspiratory, expiratory or biphasic . Inspiratory stridor is common...
, and
low oxygen Hypoxemia is generally defined as decreased partial pressure of oxygen in blood, sometimes specifically as less than or causing hemoglobin oxygen saturation of less than 90%.-Distinction from anemia and hypoxia:...
. Gastrointestinal symptoms may include crampy
abdominal painAbdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
, diarrhea, and vomiting. Due to the presence of histamine-releasing cells in the heart, coronary artery spasm may occur with subsequent
myocardial infarctionMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
or
dysrhythmiaCardiac dysrhythmia is any of a large and heterogeneous group of conditions in which there is abnormal electrical activity in the heart. The heart beat may be too fast or too slow, and may be regular or irregular.Some arrhythmias are life-threatening medical emergencies that can result in cardiac...
even in the absence of epinephrine use. A Bezold–Jarisch reflex has been described in 10% of cases, with
slow heart rateBradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
in association with
low blood pressureIn physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
. A drop in
blood pressureBlood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
may result in a feeling of lightheadedness or loss of consciousness. There may be a loss of bladder control, a feeling of
anxietyAnxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
or of "impending doom".
Causes
Anaphylaxis can occur in response to almost any foreign substance. Common triggers include
venomVenom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
from insect bites or stings, foods, and
medicationA pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
. Foods are the most common trigger in children and young adults while medications and insect bites and stings are more common in older adults. Physical factors such as exercise (known as
exercise-induced anaphylaxisExercise-induced anaphylaxis is a syndrome in which the symptoms of anaphylaxis occur related to exercise.In some incidents, individuals experienced anaphylaxis only after combination exposure to a triggering agent and increased physical activity shortly after the ingestion of the triggering agent...
) or temperature may also act as triggers, occurring through direct effects on mast cells. During
anesthesiaAnesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
, neuromuscular blocking agents, antibiotics, and
latexLatex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
are the most common causes.
Food
Many foods can trigger anaphylaxis; this may occur upon the first known ingestion. Common triggering foods vary around the world. In Western cultures, ingestion of or exposure to peanuts, wheat, tree nuts,
shellfishShellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
, fish, milk, and eggs are the most prevalent causes.
SesameSesame is a flowering plant in the genus Sesamum. Numerous wild relatives occur in Africa and a smaller number in India. It is widely naturalized in tropical regions around the world and is cultivated for its edible seeds, which grow in pods....
is common in the Middle East, while rice and chickpea are frequently encountered as sources of anaphylaxis in Asia. Severe cases are usually the result of ingesting the allergen, but some people experience a severe reaction upon contact. Children can outgrow their allergies. By age 16, 80% of children with anaphylaxis to milk or eggs and 20% who experience isolated anaphylaxis to peanuts are able to tolerate these foods.
Medication
Any medication may potentially trigger anaphylaxis. The most common ones include antibiotics (β-lactam antibiotics in particular),
aspirinAspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
,
ibuprofenIbuprofen is a nonsteroidal anti-inflammatory drug used for relief of symptoms of arthritis, fever, as an analgesic , especially where there is an inflammatory component, and dysmenorrhea....
, and other analgesics. Chemotherapy agents and herbal preparations have also been implicated. Some medications (
vancomycinVancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...
,
morphineMorphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
,
x-ray contrastRadiocontrast agents are a type of medical contrast medium used to improve the visibility of internal bodily structures in an X-ray based imaging techniques such as computed tomography or radiography...
among others) cause anaphylaxis by directly triggering mast cell degranulation.
Venom
Venom from stinging or biting insects such as
Hymenoptera Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
(bees and wasps) or
HemipteraHemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
(kissing bugs) may induce anaphylaxis in susceptible people. Previous systemic reactions to stings is a risk factor for future anaphylaxis; however, half of fatalities have had no previous systemic reaction.
Risk factors
People with atopic diseases such as
asthmaAsthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
,
eczemaEczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
, or
allergic rhinitisAllergic rhinitis, also known as pollenosis or hay fever, is an allergic inflammation of the nasal airways.It occurs when an allergen, such as pollen, dust or animal dander is inhaled by an individual with a sensitized immune system...
are at high risk of anaphylaxis from food,
latexLatex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
, and
radiocontrastRadiocontrast agents are a type of medical contrast medium used to improve the visibility of internal bodily structures in an X-ray based imaging techniques such as computed tomography or radiography...
but not injectable medications or stings. One study in children found that 60% had a history of previous atopic diseases, and of those who die from anaphylaxis more than 90% have asthma. Those with
mastocytosisMastocytosis is a group of rare disorders of both children and adults caused by the presence of too many mast cells and CD34+ mast cell precursors in a person's body.- Classification :Mastocytosis can occur in a variety of forms:...
are also at increased risk. The wealthy also appear to be a greater risk.
Pathophysiology
Anaphylaxis is a severe allergic reaction of rapid onset affecting many body systems. It is due to the release of inflammatory mediators and cytokines from
mast cellA mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...
s and basophils, typically due to an
immunologic reactionAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
but sometimes non-immunologic mechanism. The immunologic reactions can be either
immunoglobulin EImmunoglobulin E is a class of antibody that has been found only in mammals. IgE is a monomeric antibody with 4 Ig-like domains...
dependent or independent.
Immunologic
The immunologic pathophysiology is divided into two main pathways Immunoglobin E (IgE)-dependent and IgE-independent. The IgE-dependent reactions are caused by the cross linking of
receptorsIn biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...
on mast cells and basophils by an
antigenAn antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
which than triggers the release of mediators such as
histamineHistamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
. These mediators subsequently increase the contraction of
smooth muscleSmooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
s and increase the leakage of fluid from blood vessels. The IgE-independent mechanism involves
immunoglobulin GImmunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%...
and the release of platelet activating factor but not
histamineHistamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
. It has not yet been determined if this mechanism occurs in humans.
Non-immunologic
Non-immunologic mechanisms involved substances that directly cause the
degranulationDegranulation is a cellular process that releases antimicrobial cytotoxic molecules from secretory vesicles called granules found inside some cells...
of mast cells and basophils. These include agents such as temperature,
contrast mediumA medical contrast medium is a substance used to enhance the contrast of structures or fluids within the body in medical imaging...
, vibration, and opioids.
Diagnosis
Anaphylaxis is diagnosed based on clinical criteria. When any one of the following three is true there is a high likelihood of anaphylaxis:
- Symptom onset within minutes to several hours with involvement of the skin or mucosal tissue plus either respiratory difficulty or a low blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
.
- Any two or more of the following symptoms within minutes to several hours of allergen exposure: a. involvement of the skin or mucosa b. respiratory difficulties c. low blood pressure d. gastrointestinal symptoms
- Low blood pressure within minutes to several hours after exposure to known allergen
During an attack blood tests for
tryptaseTryptase is the most abundant secretory granule-derived serine proteinase contained in mast cells that has been used as a marker for mast cell activation. It is involved with allergenic response and is suspected to act as a mitogen for fibroblast lines...
or
histamineHistamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
(released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications but are of limited utility if the cause is food or the person has a normal
blood pressureBlood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
. They however are not
specificSensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
for the diagnosis.
Allergy testing
Allergy testing may help in determining the trigger.
Skin allergy testSkin allergy testing is a method for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response. -Process:A microscopic amount of an allergen is introduced to a patient's skin by various means:...
ing (with or without patch testing) is available for certain foods and venoms. Blood test for IgE levels can be useful to confirm milk, egg, peanut, tree nut and fish allergies. Skin testing is available to confirm
penicillinPenicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
allergies but is not available for other medications. Non immune forms of anaphylaxis can only be determined by history or exposure to the allergen in question and not by either skin or blood testing.
Classification
There are three main classifications of anaphylaxis. Anaphylactic shock is associated with systemic
vasodilationVasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
that results in
low blood pressureIn physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
or shock. Biphasic anaphylaxis is the recurrence of symptoms within 1–72 hours with no further exposure to the allergen. Reports of incidence vary, with some studies claiming as many as 20% of cases. The recurrence typically occurs within 8 hours. It is managed in the same manner as anaphylaxis. Pseudoanaphylaxis or anaphylactoid reactions are a type of anaphylaxis which does not involve an allergic reaction but is due to direct
mast cellA mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...
degranulation. Non-immune anaphylaxis is the current term use by the
World Allergy OrganizationThe World Allergy Organization is an international health organization founded in 1951 focused on the study of allergy. The WHO is a member of its Council for International Organizations of Medical Science of the is affiliated with the World Health Organization. It consists of 77 regional and...
with some recommending that the old terminology no longer be used.
Differential diagnosis
It can sometimes be difficult to distinguish anaphylaxis from
asthmaAsthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
, syncopy, and panic attacks. Asthma however typically does not have itching or gastrointestinal symptoms, syncope presents with pallor rather than a rash, and panic attacks while it may have flushing does not have hives. Other conditions that may present similarly include: scrombroidosis and anisakiasis.
Prevention
Avoidance of the trigger of anaphylaxis is recommended. In cases where this may not be possible or exposure is important, desensitization may be an option.
ImmunotherapyImmunotherapy is a medical term defined as the "treatment of disease by inducing, enhancing, or suppressing an immune response". Immunotherapies designed to elicit or amplify an immune response are classified as activation immunotherapies. While immunotherapies that reduce or suppress are...
with
Hymenoptera Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
venoms is effective at desensitizing 80–90% of adults and 98% of children against allergies to
beeBees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
s,
waspThe term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
s,
hornetHornets are the largest eusocial wasps; some species can reach up to in length. The true hornets make up the genus Vespa and are distinguished from other vespines by the width of the vertex , which is proportionally larger in Vespa and by the anteriorly rounded gasters .- Life cycle :In...
s,
yellowjacketYellowjacket is the common name in North America for predatory wasps of the genera Vespula and Dolichovespula. Members of these genera are known simply as "wasps" in other English-speaking countries...
s, and fire ants. Oral immunotherapy may be effective at desensitizing some people to certain food including mild, eggs, nuts and peanuts however adverse effects are common. Desensitization is also possible for many medications however it is advised that most people simply avoid the agent in question. In those who react to latex it may be important to avoid cross reactive foods such as avocados, bananas, and potatoes among others.
Management
Anaphylaxis is a
medical emergencyA medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
that may require resuscitation measures such as
airway managementIn cardiopulmonary resuscitation, anaesthesia, emergency medicine, intensive care medicine and first aid, airway management is the process of ensuring that:# there is an open pathway between a patient’s lungs and the outside world, and...
, supplemental oxygen, large volumes of intravenous fluids, and close monitoring. Administration of epinephrine is the treatment of choice with antihistamines and steroids often used as adjuncts. A period of in hospital observation for between 4 and 24 hours is recommended for people once they have returned to normal due to concerns of biphasic anaphylaxis.
Epinephrine
EpinephrineEpinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
(adrenaline) is the primary treatment for anaphylaxis with no absolute contraindication to its use. It is recommended that it be given intramuscularly into the mid anterolaterial thigh as soon as the diagnosis is suspected at a dose of 0.5 mg / 500
µgIn the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
or 0.5 mL in adults and 0.01 mg/kg in children to a maximum of 0.3 mg of 1 in 1000 solution. The dose may be repeated every 5 to 15 minutes if there is insufficient response. A second dose is needed in 16 to 35% of episodes with more than two doses rarely required. Minor adverse effects from epinephrine include
tremorA tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...
s,
anxietyAnxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
, headaches, and palpitations.
People on B-blockers may be resistant to the effects of epinephrine. In this situation if epinephrine is not effective intravenous
glucagonGlucagon, a hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood sugar levels fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is...
can be administered which has a mechanism of action independent of β-receptors.
If necessary, it can also be given
intravenouslyIntravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
using a dilute 1 in 10,000 epinephrine solution.
Epinephrine autoinjectorAn epinephrine autoinjector is a medical device used to deliver a measured dose of epinephrine using autoinjector technology, most frequently for the treatment of acute allergic reactions to avoid or treat the onset of anaphylactic shock.Trade names for this device include EpiPen, Twinject,...
used for self-administration contain a dose of 300 µg (0.3 mL of a 1 in 1000 solution) for adults or children who weight more than 25 kg and 150 µg (0.3ml of a 1:2000 solution) for children who weight 10 to 25 kg .
Adjuncts
Antihistamines (both H1 and H2), while commonly used and assumed effective based on theoretical reasoning, are poorly supported by evidence. A 2007 Cochrane review did not find any good-quality studies upon which to base recommendations and they are not believed to have an effect on airway edema or spasm. Corticosteroids are unlikely to make a difference in the current episode of anaphylaxis, but may be used in the hope of decreasing the risk of biphasic anaphylaxis. Their prophylactic effectiveness in these situations is uncertain. Nebulized
salbutamolSalbutamol or albuterol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It is marketed as Ventolin among other brand names....
may be effective for
bronchospasmBronchospasm or a bronchial spasm is a sudden constriction of the muscles in the walls of the bronchioles. It is caused by the release of substances from mast cells or basophils under the influence of anaphylatoxins...
that does not resolve with epinephrine.
Methylene blueMethylene blue is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such as biology and chemistry. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in...
has been used in those not responsive to other measures due to its presumed effect of relaxing smooth muscle.
Preparedness
People prone to anaphylaxis are advised to have an "allergy action plan", and parents are advised to inform schools, etc. of their children's allergies and what to do in case of an anaphylactic emergency. The action plan usually includes use of epinephrine auto-injectors, the recommendation to wear a medical alert bracelet, and counseling on avoidance of triggers. Immunotherapy is available for certain triggers to prevent future episodes of anaphylaxis. A multi–year course of subcutaneous desensitization has been found effective against stinging insects, while oral desensitization is effective for many foods.
Prognosis
There have been cases of death occurring with minutes. Mortality if it occurs is usually due to either respiratory (
asphyxiaAsphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...
typically) or cardiovascular causes (shock).
Epidemiology
Lifetime prevalence of anaphylaxis is estimated at between 0.05–2% globally or 4 to 50 per 100,000 persons per year. Rates appear to be increasing: prevalence in the 1980s was approximately 20 per 100,000 per year, while in the 1990s it was 50 per 100,000 per year. The increase appears to be primarily for food-induced anaphylaxis. The risk is greatest in young people and females.
Anaphylaxis as of 2010s leads to about 500–1,000 death per year (2.4 per million) in the United States, 20 deaths per year in the United Kingdom (0.33 per million), and 15 deaths per year in Australia (0.64 per million). Mortality rates have decreased between the 1970s and 2000s. In Australia death from food induced anaphylaxis occur primarily in women while deaths due to insect bites primarily occur in males. Death from anaphylaxis is most commonly triggered by medications.
History
The term "aphylaxis" was coined by Charles Richet in 1902 and later changed to "anaphylaxis" due to its nicer quality of speech. The phenomina itself however has been described since ancient times. The term comes from the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words ἀνά ana,
against, and φύλαξις phylaxis,
protection.
Research
The are ongoing efforts to develop
sublingualSublingual, literally 'under the tongue', from Latin, refers to the pharmacological route of administration by which drugs diffuse into the blood through tissues under the tongue...
epinephrine to treat anaphylaxis.
Subcutaneous injectionA subcutaneous injection is administered as a bolus into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the...
s of the anti-IgE antibodies
omalizumabOmalizumab is a humanized antibody drug approved for patients with moderate-to-severe or severe allergic asthma, which is caused by hypersensitivity reactions to certain harmless environmental substances...
is being studied as a method of preventing recurrence but is not recommended at this point in time.
External links