Anaphylaxis is a serious allergic
reaction that is rapid in onset and may cause death. It typically causes more
than one of the following: an itchy rash, throat or tongue swelling, shortness
of breath, vomiting, lightheadedness, and low blood pressure. These symptoms
typically come on over minutes to hours.
Common causes include insect bites and stings, foods, and medications. Other causes include latex exposure and exercise. Additionally, cases may occur without an obvious reason. The mechanism involves the release of mediators from certain types of white blood cells triggered by either immunologic or non-immunologic mechanisms. Diagnosis is based on the presenting symptoms and signs after exposure to a potential allergen.
The primary treatment of anaphylaxis is epinephrine injection into a muscle, intravenous fluids, and positioning the person flat. Additional doses of epinephrine may be required. Other measures, such as antihistamines and steroids, are complementary. Carrying an epinephrine auto-injector and identification regarding the condition is recommended in people with a history of anaphylaxis.
Worldwide, 0.05–2% of the population is estimated to experience anaphylaxis at some point in life. Rates appear to be increasing. It occurs most often in young people and females. Of people who go to a hospital with anaphylaxis in the United States about 99.7% survive. The term comes from the Ancient Greek: ἀνά, romanized: ana, lit. 'against', and the Ancient Greek: φύλαξις, romanized: phylaxis, lit. 'protection'.
Causes of Anaphylaxis
Anaphylaxis can occur in response to almost any foreign substance. Common triggers include venom from insect bites or stings, foods, and medication. Foods are the most common trigger n children and young adults while medications and insect bites and stings are more common in older adults. Less common causes include: physical factors, biological agents such as semen, latex, hormonal changes, food additives such as monosodium glutamate and food colors, and topical medications. Physical factors such as exercise (known as exercise-induced anaphylaxis) or temperature (either hot or cold) may also act as triggers through their direct effects on mast cells. Events caused by exercise are frequently associated with the ingestion of certain foods. During anesthesia, neuromuscular blocking agents, antibiotics, and latex are the most common causes. The cause remains unknown in 32–50% of cases, referred to as "idiopathic anaphylaxis." Six vaccines (MMR, varicella, influenza, hepatitis B, tetanus, meningococcal) are recognized as a cause for anaphylaxis, and HPV may cause anaphylaxis as well. Physical exercise is an uncommon cause of anaphylaxis; in about a third of such cases there is a co-factor like taking an NSAID or eating a specific food prior to exercising.
Diagnosis
Anaphylaxis is diagnosed on the basis of a person's signs and symptoms. When any one of the following three occurs within minutes or hours of exposure to an allergen there is a high likelihood of anaphylaxis:
a. Involvement of the skin or mucosa
b. Respiratory difficulties
c. Low blood pressure
d. Gastrointestinal symptoms
Skin involvement may include: hives, itchiness or a swollen tongue among others. Respiratory difficulties may include: shortness of breath, stridor, or low oxygen levels among others. Low blood pressure is defined as a greater than 30% decrease from a person's usual blood pressure. In adults a systolic blood pressure of less than 90 mmHg is often used.
During an attack, blood tests for tryptase or histamine (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications. However these tests are of limited use if the cause is food or if the person has a normal blood pressure, and they are not specific for the diagnosis.
Prevention
Avoidance of the trigger of anaphylaxis is recommended. In cases where this may not be possible, desensitization may be an option. Immunotherapy with Hymenoptera venoms is effective at desensitizing 80–90% of adults and 98% of children against allergies to bees, wasps, hornets, yellowjackets, and fire ants. Oral immunotherapy may be effective at desensitizing some people to certain food including milk, eggs, nuts and peanuts; however, adverse effects are common. For example, many people develop an itchy throat, cough, or lip swelling during immunotherapy.
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 emergency that may require resuscitation measures such as airway management, supplemental oxygen, large volumes of intravenous fluids, and close monitoring. Passive leg raise may also be helpful in the emergency management.
Administration of epinephrine is the treatment of choice with antihistamines and steroids (for example, dexamethasone) often used as adjuncts. A period of in-hospital observation for between 2 and 24 hours is recommended for people once they have returned to normal due to concerns of biphasic anaphylaxis.
https://en.wikipedia.org/wiki/Anaphylaxis
Common causes include insect bites and stings, foods, and medications. Other causes include latex exposure and exercise. Additionally, cases may occur without an obvious reason. The mechanism involves the release of mediators from certain types of white blood cells triggered by either immunologic or non-immunologic mechanisms. Diagnosis is based on the presenting symptoms and signs after exposure to a potential allergen.
The primary treatment of anaphylaxis is epinephrine injection into a muscle, intravenous fluids, and positioning the person flat. Additional doses of epinephrine may be required. Other measures, such as antihistamines and steroids, are complementary. Carrying an epinephrine auto-injector and identification regarding the condition is recommended in people with a history of anaphylaxis.
Worldwide, 0.05–2% of the population is estimated to experience anaphylaxis at some point in life. Rates appear to be increasing. It occurs most often in young people and females. Of people who go to a hospital with anaphylaxis in the United States about 99.7% survive. The term comes from the Ancient Greek: ἀνά, romanized: ana, lit. 'against', and the Ancient Greek: φύλαξις, romanized: phylaxis, lit. 'protection'.
Causes of Anaphylaxis
Anaphylaxis can occur in response to almost any foreign substance. Common triggers include venom from insect bites or stings, foods, and medication. Foods are the most common trigger n children and young adults while medications and insect bites and stings are more common in older adults. Less common causes include: physical factors, biological agents such as semen, latex, hormonal changes, food additives such as monosodium glutamate and food colors, and topical medications. Physical factors such as exercise (known as exercise-induced anaphylaxis) or temperature (either hot or cold) may also act as triggers through their direct effects on mast cells. Events caused by exercise are frequently associated with the ingestion of certain foods. During anesthesia, neuromuscular blocking agents, antibiotics, and latex are the most common causes. The cause remains unknown in 32–50% of cases, referred to as "idiopathic anaphylaxis." Six vaccines (MMR, varicella, influenza, hepatitis B, tetanus, meningococcal) are recognized as a cause for anaphylaxis, and HPV may cause anaphylaxis as well. Physical exercise is an uncommon cause of anaphylaxis; in about a third of such cases there is a co-factor like taking an NSAID or eating a specific food prior to exercising.
Diagnosis
Anaphylaxis is diagnosed on the basis of a person's signs and symptoms. When any one of the following three occurs within minutes or hours of exposure to an allergen there is a high likelihood of anaphylaxis:
- Involvement of the skin or mucosal tissue plus either respiratory difficulty or a low blood pressure causing symptoms
- Two or more of the following symptoms after a likely contact with an allergen:
a. Involvement of the skin or mucosa
b. Respiratory difficulties
c. Low blood pressure
d. Gastrointestinal symptoms
- Low blood pressure after exposure to a known allergen
Skin involvement may include: hives, itchiness or a swollen tongue among others. Respiratory difficulties may include: shortness of breath, stridor, or low oxygen levels among others. Low blood pressure is defined as a greater than 30% decrease from a person's usual blood pressure. In adults a systolic blood pressure of less than 90 mmHg is often used.
During an attack, blood tests for tryptase or histamine (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications. However these tests are of limited use if the cause is food or if the person has a normal blood pressure, and they are not specific for the diagnosis.
Prevention
Avoidance of the trigger of anaphylaxis is recommended. In cases where this may not be possible, desensitization may be an option. Immunotherapy with Hymenoptera venoms is effective at desensitizing 80–90% of adults and 98% of children against allergies to bees, wasps, hornets, yellowjackets, and fire ants. Oral immunotherapy may be effective at desensitizing some people to certain food including milk, eggs, nuts and peanuts; however, adverse effects are common. For example, many people develop an itchy throat, cough, or lip swelling during immunotherapy.
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 emergency that may require resuscitation measures such as airway management, supplemental oxygen, large volumes of intravenous fluids, and close monitoring. Passive leg raise may also be helpful in the emergency management.
Administration of epinephrine is the treatment of choice with antihistamines and steroids (for example, dexamethasone) often used as adjuncts. A period of in-hospital observation for between 2 and 24 hours is recommended for people once they have returned to normal due to concerns of biphasic anaphylaxis.
https://en.wikipedia.org/wiki/Anaphylaxis
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