Anyone can develop an allergy at any time in his or her life, even without specific risk factors. Yet some people, including asthmatics, children, and those with a history of anaphylaxis, have an increased susceptibility to allergic reactions. The likelihood and severity of experiencing a repeat allergic reaction depends largely upon the type of allergen and the individual's sensitivity to it.

Susceptibility

A serious and potentially life-threatening allergic reaction is most likely to occur in people:

With a history of allergies1

Who have asthma and a food allergy2,3

Who have previously experienced anaphylaxis7,8

Children, whose immune systems are immature, are most susceptible to a broad array of food allergies.

The immune system is responsible for guarding the body against perceived invaders, including allergens.

Likelihood and Severity of Repeat Reactions

People frequently outgrow allergies to milk, soybeans, and eggs when they leave childhood, but peanuts, tree nuts, and shellfish tend to be lifelong allergens.4-6

Sensitivity to insect stings frequently decreases over time or stops altogether, particularly among children. However, according to one study, people who have experienced an allergic reaction to insect venom have a 30% to 60% chance of experiencing a similar or more severe response if stung again.7

In fact, it is impossible to predict the severity of future anaphylactic reactions in any particular person. There is no set pattern, but the severity of an allergic reaction is thought to depend on:

The amount of allergen to which a patient is exposed

The individual's degree of hypersensitivity to the allergen

This can vary according to the health of the patient at the time of exposure and can be exacerbated by other factors such as exercise or co-ingestion of alcohol along with food allergens

In general, once a reaction has begun, and the more rapidly symptoms appears, it is more likely the reaction will be severe.

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