How Does a Peanut Allergy Develop? About Early & Adult Onset Peanut Allergy

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Peanut allergies have become more prevalent in Western populations in the last few years. They now affect approximately 1% of schoolchildren in the United States and the United Kingdom (Sicherer and Sampson 2007). Over half of anaphylaxis deaths in the U.S. are attributed to peanut allergy, though they were a less common trigger for anaphylaxis death in the U.K. (Sicherer and Sampson 2007).

Peanut allergies are notorious for causing reactions from exposure to even tiny amounts. One study (Flinterman et al. 2006) showed that amounts as little as 10 mg could cause children to report reactions, though objective symptoms were not observed at levels under 100 mg. Alarmingly, the researchers were not able to use allergy test results to predict how much peanut allergen would cause a response. But how does a peanut allergy develop?

Age of Onset of Peanut Allergy

Peanut allergy sufferers can be divided into two groups: early and late onset. The first group typically experienced the first reaction in childhood, at a median age of three years, while the second typically experienced the first reaction in adulthood, at a median age of 25 years.

Early onset patients first reacted to peanuts on one of their first exposures, but late onset patients were able to eat peanuts with no problems for years before they experienced their first reaction. Early onset patients are more likely to have severe reactions than late onset patients. They also had a larger amount of peanut-specific antibodies (pn-IgE). In both groups, some subjects saw their peanut allergy disappear eventually. (Savage et al. 2007)

Life With a Peanut Allergy

When a child suffers a peanut allergy, the diligent avoidance of peanuts has a significant negative impact social and family life (Primeau et al. 2000). Both children and parents reported disruption in their daily lives because of the necessities of living with a peanut allergy. The same study showed that there may be less life disruption if the allergic person is an adult.

Anecdotal evidence shows that avoiding peanuts can actually exacerbate the severity of the allergic response. One patient with late onset peanut allergy experienced her first peanut reaction with a mild response. Though peanuts had previously been a part of her normal diet, she began to avoid them on the advice of doctors. Years later, her reactions were more severe, possibly because once she stopped being exposed to peanuts, her tolerance decreased (Savage et al. 2007) Thus an avoidance diet can have the opposite effect of immunotherapy. Still, patients should follow an avoidance diet if advised by their health care practitioners because allergic reactions can be unpredictable.