About 30 of every 100,000 people experience food-induced anaphylaxis. An anaphylactic reaction should always be considered a medical emergency. Symptoms generally appear as soon as someone who is hypersensitive swallows a food allergen. The symptoms may not appear until up to four hours after exposure. How swiftly an anaphylactic reaction begins and how severe it becomes depends on:
- the sensitivity of an individual to the allergen.
- the amount of allergen swallowed.
- how many different food allergens were consumed.
- food preparation.
- precipitating medical conditions.
An anaphylactic reaction may begin with tingling, itching, or a metallic taste in the mouth. Even the mildest symptoms can become severe within a short time. Anaphylactic reactions can go on for hours. They may include:
- wheezing and other breathing problems.
- swelling of the mouth and throat.
- cramps and nausea.
- rapid pulse and sudden drop in blood pressure.
- hives and flushing.
- itching of the palms of the hands and the soles of the feet.
- loss of consciousness.
Anaphylaxis can be a biphasic reaction: New, more severe symptoms sometimes appear as long as two to six hours after the initial wave of symptoms has receded. These recurring symptoms often involve the respiratory system and can be deadly.
Peanuts and tree nuts are the foods most likely to cause severe food-allergic reactions. The other most common causes of anaphylaxis attributed to food allergies are:
People who have asthma and food allergies are thought to have a greater than average risk of developing a food-allergic anaphylactic reaction. Having experienced one or more severe allergic reactions also increases the likelihood that an individual will have an anaphylactic reaction in the future.
The risk of fatal anaphylactic reaction is greatest among adolescents who have asthma and allergies to peanuts and tree nuts but disregard early food allergy symptoms and do not have ready access to epinephrine. Used to halt the progress of an anaphylactic reaction and reverse its symptoms, this drug is self-administered by injection. Epinephrine is often prescribed for individuals with a history of severe allergic reaction