Anaphylaxis is a rapid, immune-mediated (allergic), systemic reaction to allergens (like food, medication or insect stings) that the individual has previously been exposed to. Anaphylaxis is a medical emergency that requires immediate medical treatment, as well as follow-up care with an allergist or immunologist.
Symptoms of anaphylaxis can vary from mild to severe and may be potentially life threatening. The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal. The most severe type of anaphylaxis, known as anaphylactic shock, will usually result in death within minutes, if untreated. Anaphylactic shock is characterized by inflammation of the throat and a sudden drop in blood pressure.
Even trace amounts of the allergen can result in a life-threatening anaphylactic reaction. Anaphylaxis may occur after inhalation, ingestion, skin contact or injection of an allergen.
Anaphylaxis, similar to other allergic reactions, involves the immune system. Typically, an allergic response is not triggered the first time the body encounters the allergen. The first time or several times after the body is exposed to an allergen, the immune system becomes sensitized and prepares to react to the next encounter with the allergen. Once sensitized, the immune system can quickly detect the drug in the body and produce immunoglobulin E (IgE). These antibodies trigger the release of chemical mediators, including histamine, which cause allergic symptoms and anaphylaxis.
Researchers distinguish between "true anaphylaxis" and "pseudo-anaphylaxis." The symptoms, treatment and fatality risk are the same for both conditions. However, "true anaphylaxis" is directly caused by the immunoglobulin E (IgE)-mediated degranulation of mast cells or basophils. Pseudo-anaphylaxis, on the other hand, is not mediated by antibodies. The distinction is important for researchers who are studying the mechanisms of allergic reactions. However, the distinction does not affect treatment options.
Anaphylaxis is a systemic reaction, which means that many parts of the body are affected.
The time lapse between ingestion/or contact with the allergen and anaphylactic symptoms varies among individuals. Symptoms can appear immediately or can be delayed from 30 minutes to one hour after exposure. Symptoms may also disappear and then recur hours later. Once symptoms arise, they progress quickly.
Symptoms of anaphylaxis can vary from mild to severe and are potentially deadly. The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal.
Cardiovascular: Reported symptoms include, hypotension, chest pain or tightness, cardiac arrest, faint pulse and shock.
Dermatologic: Reported symptoms include, urticaria, swelling, itchy skin, sensation of warmth, reddening of the skin, flushing, angioedema and rash.
Pulmonary: Histamine can induce vasodilatation of arterioles and constriction of bronchioles in the lungs, also known as bronchospasm. Other symptoms may include respiratory distress, throat tightness, hoarse voice, cough, nasal congestion, trouble swallowing, fainting, light-headedness, unconsciousness, angioedema, wheezing, respiratory arrest and death.
Other: Other possible symptoms include anxiety, hay fever-like symptoms, red/itchy/watery eyes, headache and cramping of the uterus.
Anaphylaxis is an emergency condition that requires immediate medical attention.
CPR should be initiated if the individual is not breathing.
Epinephrine is a medication used to treat severe allergic reactions that can result in anaphylaxis. Administering the epinephrine as soon as possible improves the chances of survival and a quick recovery. Epinephrine opens the airways and raises the blood pressure by constricting blood vessels. Patients may also be admitted to the hospital to have their blood pressure monitored and possibly to receive breathing support.
Other emergency interventions may also include endotracheal intubation (placing a tube through the nose or mouth into the airway) or emergency surgery to place a tube directly into the trachea (tracheostomy or cricothyrotomy).
Hypotension is usually treated with intravenous fluids and sometimes with vasoconstrictive medications also referred to as "pressors."
Bronchodilator drugs like Salbutamol® (known as Albuterol® in the United States) are used to treat bronchospasm.
After epinephrine are other lifesaving measures are taken, antihistamines (like diphenhydramine) and corticosteroids (like prednisone) may be given to further reduce symptoms.
Individuals with a history of anaphylaxis should carry an autoinjectable epinephrine device (known as an EpiPen®) with them at all times.
Anaphylaxis is considered a medical emergency that requires immediate medical care. Therefore, complementary and alternative therapies should not be used in place of conventional medicine when an individual has an anaphylactic reaction.
Individuals who have a history of allergy to insect stings should carry an emergency kit consisting of injectable epinephrine and an antihistamine. Consider wearing a Medic-Alert or similar bracelet or necklace stating serious allergies.
Anaphylactic sensitivity can be transferred to a non-sensitive individual by exposure to fluid that contains the antibodies. This is referred to as passive transfer of the allergy. For instance, there have been some reported fatalities, which have resulted from passive transfer involving organ transplants.
Although rare, exercise may trigger anaphylaxis. The reaction does not (necessarily) occur after every exercise session. In some cases, eating certain types of foods before exercising may also trigger anaphylaxis. Foods that have triggered anaphylaxis in reported cases include wheat, cheese, seafood and celery.
Food: It is possible for any kind of food to trigger an allergic reaction. However, some of the most common foods that cause severe anaphylaxis include: peanuts, nuts from trees (like walnuts, cashews or Brazil nuts), shellfish, fish, milk and eggs. According to the American Academy of Allergy Asthma & Immunology (AAAAI), about 100 people in the United States die each year from food-related anaphylaxis.
Most people who are stung by insects like yellow jackets, honeybees, paper wasps, hornets or fire ants experience discomfort and minor swelling. However, individuals who are allergic to insect venom can potentially experience life-threatening reactions to a sting. According to the AAAAI, anaphylaxis occurs in 0.5 to 5% of the U.S. population as a result of insect stings. At least 40 Americans die each year from anaphylactic reactions to insect stings.
Some products made from natural latex (like gloves, balloons and condoms) contain allergens that can trigger anaphylactic reactions in allergic individuals. Anaphylactic reactions are the greatest threat when the latex comes into contact with moist areas of the body or internal surfaces during surgery because more of the allergen can rapidly enter the body. According to the AAAAI, about 220 cases of anaphylaxis and three deaths per year are attributed to latex allergies.
Essentially any medication can potentially cause an allergic reaction. Anaphylaxis most commonly occurs after exposure to antibiotics and anti-seizure medicines. In addition, medical therapies including, vaccines, blood, blood products, radio contrast dyes, pain medications, ACE inhibitors and other drugs may also trigger anaphylaxis.
Penicillin: The antibiotic known as penicillin is one of the most common drug allergies. According to the AAAAI, anaphylactic reactions to penicillin cause 400 deaths in the United States each year.
In rare cases, anaphylaxis has been associated with exposure to seminal fluid, hormones and extreme temperatures. When an unknown substance causes an anaphylactic reaction, it is referred to as idiopathic anaphylaxis.
The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.