Current and Emerging Immunotherapeutic Approaches to Treat and Prevent Peanut Allergy

Darren S Miller; Michael P Brown; Paul M Howley; John D Hayball

Disclosures

Expert Rev Vaccines. 2012;11(12):1471-1481. 

In This Article

The Prevalence & Natural History of Peanut Allergy

Food allergy accounts for about 30,000 anaphylactic reactions, 2000 hospitalizations and 200 deaths each year in the US alone;[1] if, as predicted, 5% of the child population of the UK and Ireland are similarly afflicted then it has been predicted that upwards of 1 in 800,000 food allergic children will die each year.[2] Peanuts are the major causative allergen with an incidence of approximately 1% of the US population,[1] a statistic also recapitulated in Europe.[1,3–5] The incidence of peanut allergy in children has shown a continued upward trajectory during the past two decades. The first evidence for this was noted from a study conducted in American children with atopic dermatitis from 1990 to 1994. Here it was concluded that the prevalence of peanut allergy had doubled from that observed in a similar group of children 10 years earlier.[6] In other long-term follow-up studies, it was shown that in the general US population, the relative incidence of peanut and/or tree nut allergies had changed little in years from 1997 (1.4%)[7] to 2002 (1.2%)[8] to 2008 (1.4%).[9] Although the adult prevalence of peanut allergy, tree nut allergy or both was similar (1.3%) in both 1997 and 2002,[7,8] the allergy rates of children (under 18 years of age) increased markedly over the same time period viz., 0.6% (1997),[7] 1.2% (2002)[8] and 2.1% (2008).[9]

The basis for the observed increase in peanut allergy among children is poorly understood. However, as vegetarian diets become more popular and as the demand for preprepared nutritional foods grows, peanut exposure has increased in pregnant and nursing mothers and in infants.[10,11] Consequently, virtually all children in the USA are exposed to peanuts by the age of two.[12] Owing to the relative immaturity of the infant immune system, immunoreactivity to food is more likely to develop during the first few years of life. Importantly, increased exposure throughout childhood translates into increased peanut sensitization in genetically predisposed children.[13]

The initial reaction to peanuts typically occurs at a median age of 14–24 months,[14,15] and unlike milk and egg allergies, most (but not all[16]) peanut-allergic patients do not outgrow their peanut sensitivities.[10] For the majority of patients who continue to have clinical sensitivities to peanuts, reactions may become more severe with time.[10] Many studies have similarly shown that 72–81% of peanut-allergic patients react to peanuts on their first known ingestion and the severity of subsequent responses is more often than not similar,[14,17] but up to a third of the patients with mild initial reactions develop severe symptoms on subsequent exposures.[17]

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