MIAMI – Food allergies in children appear to be increasing in prevalence, can be diagnosed based on history and testing, and are often best managed using a multidisciplinary approach and careful follow-up, Dr. Vivian Hernandez-Trujillo said.
Counsel patients and families on how to recognize symptoms and avoid certain allergens. Also educate them to prepare for future emergencies, including instruction on the use of self-injected epinephrine. Unfortunately, even if a child has had only mild allergic reactions, there is no guarantee the next episode will not be more serious, Dr. Hernandez-Trujillo said.
Dr. Vivian Hernandez-Trujillo
Although children can have allergic reactions to any food, six types are responsible for 90% of reactions. These are milk, eggs, peanuts, wheat, soy, and tree nuts.
“Cow’s milk, eggs, and soy [reactions] are most common in kids. And allergies to peanuts, tree nuts, seafood, and seeds tend to persist – that is a take-home message,” Dr. Hernandez-Trujillo said at a pediatric update sponsored by Miami Children’s Hospital.
Diagnosis relies on “history, history, and history.” A personal and family history of allergy, exposure to common allergenic foods, and the presence of other allergic diseases such as asthma or rhinitis are important considerations. Risk, for example, is four times greater with a positive family history of asthma. Diet diaries also are very important, particularly when working with an allergist and nutritionist. “I always involve nutritionists – we are a team,” said Dr. Hernandez-Trujillo, director of the division of allergy and immunology at the hospital.
Elimination diets, skin testing, in vitro assays, and food challenges also have roles in diagnosis, she said.
The length of time between ingestion and symptoms can help to distinguish between the two main types of allergic reactions to food protein: IgE mediated and non–IgE mediated. IgE-mediated reactions can produce signs and symptoms within 20 minutes versus 2 hours to several days for non-IgE reactions.
IgE-type reactions can be more serious, even life threatening, because they include anaphylaxis. An estimated 150 people die each year of fatal food anaphylaxis. "This is a striking number,” Dr. Hernandez-Trujillo said. Respiratory symptoms are prominent. “Cutaneous symptoms may not be present – if they are not there, it may be very frightening,” she added.
Factors that increase the risk for fatal anaphylaxis include a history of severe reactions, underlying asthma, delayed use of epinephrine, and symptom denial among adolescents and young adults.
Caution is warranted in children younger than 1 year because of a higher rate of false-negative skin test results, Dr. Hernandez-Trujillo said. “It is still worth testing them if you catch a positive.”
Skin prick testing has a negative predictive value of 95% or more, but a positive predictive value of only 50%. Although this testing is not recommended for screening, selective use for a suspected food makes sense, Dr. Hernandez-Trujillo said. She added, “We never do intradermals. They are risky and have a high false-positive rate.”
If a test for a specific IgE antibody is negative, reintroduce food, Dr. Hernandez-Trujillo said. If there is a positive antibody assay, start an elimination diet.
Symptoms of non-IgE allergic food hypersensitivity – protracted vomiting and/or diarrhea, dehydration – can resolve within 72 hours of food avoidance.
Elimination diets of 1-6 weeks are very important with non–IgE-mediated disease as well. Eliminate the suspected food, if known, or put the patient on a very strict elemental diet, she recommended. Oral challenge testing should be done only under physician supervision with emergency medications available, Dr. Hernandez-Trujillo.
When it comes to management of food allergy, “I frequently consult a nutritionist,” she said. A decision on whether to rechallenge a patient depends on the type of food allergy, the severity of symptoms experienced in the past, and the specific allergen involved. A periodic reevaluation for tolerance is helpful, she said. Tolerance is suggested if concentrations of food-specific IgE levels decrease over time.
An estimated 2.2 million school-aged children have food allergy (J. Allergy Clin. Immunol. 2001;107:191-3). Although public perception of prevalence is higher at around 20%-25%, oral challenge testing puts the figures between 6% and 8% for infants and young children and 2.0%-3.5% for adults. Children with atopic dermatitis, latex allergy, and certain allergies to pollen will experience higher rates, Dr. Hernandez-Trujillo said.