Anju Peters, MD, Updates Doctors on the Knowns and Unknowns of Food Allergy
MAY 14, 2017
“You all get faced with questions about food allergies all the time,” she told a room full of primary care physicians, “Compared to other medical conditions, the mortality with food allergies is quite low, but as you can imagine, the risk, worrying about anaphylaxis, plays a huge role…so it really effects quality of life.”
Her speech primarily centered on immunoglobin E (IgE) mechanisms in food allergies, asking questions of prevalence, manifestations, and prevention.
True prevalence of IgE mediated food allergies is not known, but 6 to 8% of children and 2 to 3% of adults in the US are estimated to have one or more. It may appear there has been an increase in prevalence, but whether that’s just a matter of diagnosis and reporting is unknown. According to survey studies, 12% of kids and 15% of adults think that they have one, clearly inconsistent with even the more generous estimates. They might actually be increasing, Dr. Peters concedes, as comparison of US National Health studies showed a population prevalence that went from under 4% in a 1997 study to over 5% in a 2011 one.
Patterns of distribution can be discerned: boys, African-Americans, and second-generation Asians are more likely to have food allergies, and comorbid diseases are very common. Those with one have a 35-70% chance of having atopic dermatitis according to various estimates, a 34-49% chance of having asthma, and a 35-40% of having allergic rhinitis.
Their presentation can be quite variable, Peters says. Manifestations come in a range of forms, and 80-90% of food allergy sufferers show some sort of skin reaction (hives, worsening eczema, flushing), 60-70% have respiratory reactions, 40% some gastrological disturbance, and 30% may have cardiovascular symptoms, which are the most common linked to death.
Family history, a physical, symptom presence, timing, and reproducibility are all essential for diagnosis of a food allergy. If symptoms do not manifest within 4 hours of consumption, Peters believes a doctor can confidently rule out an allergy. And if a patient claims a previous recent reaction to a food but can soon after eat that food again without symptoms, it isn’t likely that they are actually allergic. “Not possible,” Peters declared.
Family history isn’t alone a great predictor, so all these can be supplemented with laboratory measures like serum specific IgE tests and skin tests. The outcomes of serum IgE tests can be extremely consistent if done correctly, “but all they tell you is if someone has the IgE antibody…in fact, these tests have 50% false positives,” Peters explained. “The good part though is if you have a negative skin test or a negative serum-specific IgE, you can pretty much rule out food allergy,” and she said those negatives are good for reassuring patients that whatever issue they are having is not food allergy, allowing treatment of the issue to move on to find out what is actually causing the patient’s symptoms.
Treatment has, of course, remained limited to epinephrine and antihistamines. It is essential, Peters notes, to not just prescribe epi pens, but to show patients how and when to use them.
There has not been much settled on the preventability of food allergies. Currently, Peters says there is no evidence in favor of maternal avoidance diets or probiotics. That said, she pointed to the LEAP “Learning Early About Peanut” study that was published in the New England Journal of Medicine in 2015, which randomized 4-6 month old children who were deemed “high risk” for food allergy due to other allergic conditions. One group consumed peanuts, and the other was made to avoid until 5 years of age. In the avoidance group at 60 months, 13.7% had peanut allergy as opposed to less than 2% in the consumption group.
“In fact, it’s now recommended to introduce peanuts at 4 to 6 months of age,” Peters said.