What is anaphylaxis?
Anaphylaxis is a severe, life-threatening allergic response. The immune system creates specific immunoglobulin E (IgE) antibodies towards a substance that is normally harmless. The body becomes sensitized to this substance, but when the person is exposed to it again, the IgE antibodies recognize this substance and activate immune cells to release large amounts of inflammatory substances, including histamine. These substances can cause the symptoms of anaphylaxis, which may include swelling, hives, lowered blood pressure, shortness of breath, wheezing, difficulty swallowing, and loss of consciousness.
In severe cases, a person will go into anaphylactic shock. Blood pressure drops severely and swelling occurs in the bronchial tissues, causing symptoms of choking and loss of consciousness. If anaphylactic shock isn't treated immediately, it can be fatal.
What are the symptoms of anaphylaxis?
Anaphylaxis may begin with severe itching of the eyes or face and within minutes progress to more serious symptoms, including:
- swelling, which can cause difficulty swallowing and breathing
- abdominal pain
- cramps
- vomiting
- diarrhea
- hives and angioedema (swelling)
If you have symptoms of anaphylaxis, seek immediate medical attention, as the condition can quickly result in an increased heart rate, sudden weakness, a drop in blood pressure, shock, and ultimately unconsciousness and even death.
What are the most common causes of anaphylaxis?
Food allergy is a recognized cause of anaphylaxis--especially peanuts, tree nuts (for example, walnuts, hazelnuts, Brazil nuts, cashews, etc.), shellfish (for example, shrimp, lobster, etc.), cow’s milk, egg, wheat, and soy. Venom allergies (for example, allergy to bee or wasp stings) are also recognized causes of anaphylaxis.
Some substances can cause reactions, called anaphylactoid reactions, that are similar to and just as serious as anaphylaxis, but do not involve IgE antibodies. Acetylsalicylic acid (aspirin), other nonsteroidal anti-inflammatory drugs, and intravenous radiocontrast dye given for CT scans are recognized causes of these reactions.
Pollens and other inhaled allergens (allergy-causing substances) rarely cause anaphylaxis.
How is anaphylaxis diagnosed?
Anaphylaxis is diagnosed based on its symptoms. People with a history of allergic reactions may have a greater risk for developing a severe reaction in the future.
Skin testing and RAST blood tests may help confirm the substances that cause severe allergic reactions. If anaphylactic reactions are suspected, testing should be performed under the guidance of a medical professional with training and experience in selecting appropriate tests.
How is anaphylaxis treated?
The only effective treatment for acute anaphylaxis is epinephrine (adrenaline) by injection. Epinephrine works quickly to reverse anaphylactic symptoms. Epinephrine can be given through an self-delivered injection device. The most common injection site is the thigh.