Some form of immunotherapy is expected to be available for peanut allergy within the next five years. But the reasons for the increasing prevalence of this allergic reaction remain unclear. The issues are discussed by Professor Wesley Burks, Duke University Medical Center, NC, USA, in a Seminar in this week’s edition of The Lancet.
Peanut allergy has become a major health concern worldwide, especially in developed countries, and affects around 1% of children under the age of five years. It is a disease modulated by the immunoglobulin E part of the immune system - once peanut protein is ingested, it crosslinks with these IgE antibodies and causes release of inflammatory molecules such as histamines.
The mean age of diagnosis in children is 14 months, with symptoms occurring after the first known peanut ingestion in 75% of those children eating peanuts for the first time. Almost all initial reactions involve the skin, approximately half involve the respiratory tract, and a third the gastrointestinal tract.
Professor Burks says: “Because of the potentially severe health consequences of peanut allergy, those suspected of having had an allergic reaction to peanuts deserve a thorough evaluation. All patients with peanut allergy should be given an emergency management plan, as well as epinephrine and antihistamines to have on hand at all times. Patients and families should be taught to recognise early allergic reactions to peanuts and how to implement appropriate peanut-avoidance strategies. It is imperative that severe, or potentially severe, reactions be treated promptly with intramuscular epinephrine and oral antihistamines. Patients who have had such a reaction should be kept under observation in a hospital emergency department or equivalent for up to four hours because of the possible development of the late-phase allergic response.”
A study from the USA has shown that peanut allergy prevalence in young children doubled from 0.4% in 1997 to 0.8% in 2002. There are many theories regarding the increased prevalence of peanut allergy, none of them proven. Among them is the hygiene hypothesis, which says that not enough exposure to infectious agents in early childhood can increase susceptibility to allergic disease. And researchers have suggested that presence of peanuts in the mother’s diet before birth could be risk factor for developing the allergy.
Among the approaches being looked at to reduce the impact of this condition is development of transgenic plants to produce hypoallergenic peanuts. However, as several peanut proteins are involved in the allergic response, Professor Burks says: “The process of altering enough of the peanut allergens to make a modified peanut that is less likely to cause an allergic reaction would probably render the new peanut no longer a peanut.”
Future treatments are all focused around the attempt to curb the immune response or induce tolerance by the immune system in response to a specific food allergen. Possible approaches include engineered peanut proteins used as immunotherapy and specific oral tolerance induction, in which the food is ingested in increasingly larger amounts on a regular basis. Professor Burks concludes: “It is likely that in the next five years there will be some type of immunotherapy available for peanut allergenic individuals.”
http://multimedia.thelancet.com/pdf/press/peanutseminar.pdf
Journal
The Lancet