Food-related atopic dermatitis may predict childhood asthma

April 1, 2005

Boston — According to Hugh A.Sampson, knowing there is a higher incidence of asthma among children who develop atopic dermatitis (AD) and food allergy early in life makes it possible to identify those who are likely to develop the respiratory disorder.

The implications of this are clear to Dr. Sampson, who is director of the Jaffe Food Allergy Institute, professor of pediatrics and immunobiology, and chief, pediatric allergy and immunology, Mount Sinai School of Medicine, New York.

"Some day, we may be able to use this early identification to enable us to use appropriate prophylactic measures," he says.

He maintains that AD is typically the first clinical manifestation for a child prone to developing atopic disease, with 50 percent of all AD developing in the first year of life and 80 percent by 5 years of age.

"Children with AD have the highest incidence of food allergy of any identifiable patient group," he tells Dermatology Times. "If asthma is also present - as it is in the majority of children with AD - these patients are at highest risk for developing severe food anaphylactic reactions."

It is for precisely that reason that Dr. Sampson says it is imperative that physicians make the diagnosis as early as possible to identify and treat patients who are likely to benefit from effective treatment.

Candidates for treatment Dr. Sampson suggests that it may be possible to use the information learned about patients who lose their clinical reactivity to someday prevent the progression from food allergy to serious respiratory illnesses.

Knowledge of the factors that determine the likelihood that this will happen, he says, is the key to identifying patients who can benefit from effective treatment.

For example, he explains, patients allergic to peanuts, nuts, fish and shellfish are not likely to lose their clinical reactivity, whereas those allergic to soy, wheat, milk and egg are much more likely to develop clinical tolerance. Likewise, the higher the level of food antigen-specific IgE, the less likely that clinical tolerance will develop in the subsequent few years.

What's more, the degree to which the patient adheres to the prescribed elimination diet can make or break its success.

"Patients ingesting small amounts of allergen or having frequent accidental ingestions appear less likely to develop clinical tolerance," he says.

However, Dr. Sampson adds it is not yet clear whether it is a case of "the sooner, the better."

Such clinical tolerance - or the point at which a food allergy has been "outgrown" - he says, can be determined by monitoring the level of food-specific IgE.

Given the rewards for successful management of food allergy, Dr. Sampson emphasizes effective approaches to the diagnosis and management of both AD and food allergy.

Diagnosis: atopic dermatitis Dr. Sampson maintains that AD diagnosis is relatively straightforward.

"Standard diagnostic criteria exist for atopic dermatitis, which is identified by a constellation of symptoms. In addition, the SCORAD Index adapted by the European Task Force on Atopic Dermatitis provides a standardized method for gauging severity," he says.

Treatment Once food hypersensitivity is diagnosed, therapy consists of placing the patient on a diet that completely eliminates all forms of the offending allergen.

Because egg allergy is the most frequent cause of food-induced eczematous symptoms, and egg, milk, peanut, soy and wheat, combined, account for about 90 percent of food allergy in children with AD, Dr. Sampson says an empiric trial of egg and milk exclusion may be warranted in infants and young children with moderate to severe AD. However, he adds, exclusionary diets must not be prolonged without firm evidence of clinical reactivity.

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