Food allergies less common than previously thought
Thursday, July 22, 2010
The alarm over food allergies has changed day care and schools enormously. "No peanut zones" are commonplace in the lunchroom, while snack ingredient lists are subject to scrutiny by wary parents and teachers.
Yet the number of children with food allergies may not be as large as we think.
According to a federally commissioned study published in the May 10 issue of the Journal of the American Medical Association, the true incidence of food allergies is only about 8 percent in children. It's even less in adults-less than 5 percent. Yet about 30 percent of people believe they have food allergies.
Researchers from VA Palo Alto Healthcare System and Stanford University pored over more than 12,000 allergy research studies, published between January 1988 and September 2009. Surprisingly, they concluded that only 72 studies were properly conducted to yield accurate conclusions.
Other findings in the study:
- Despite popular belief, breast-fed infants do not suffer fewer allergies.
- Using probiotics along with breast milk, hypoallergenic formula, or both, may help prevent food allergies. But their effects on their own are not clear.
- Withholding eggs during the first year of life is not necessary.
- Food challenges, skin prick testing and blood tests for IgE antibodies all have a role to play in making a diagnosis. But no one test is sensitive or specific enough to be recommended over the other tests.
- While elimination diets are the mainstay of treatment, researchers could only find one randomized controlled trial-one of the most reliable study types-of an elimination diet. Part of the problem is that a randomized, controlled trial for serious life-threatening food allergy reactions is not only unnecessary, but unethical.
- It's not clear whether or not food allergies are increasing.
Why is there so much confusion?
Food allergy and food intolerance often get mixed up. Only allergies involve the immune system. Food intolerance is more common than food allergy and occurs when the digestive tract cannot properly break down food. For example, the inability to digest the milk sugar, lactose, is an intolerance.
In a November 2009 study by the journal, Pediatrics, potential ethnic differences were found. For example, black children were nearly twice as likely as white children to have IgE antibodies to peanuts, twice as likely to have antibodies to milk and four times as likely to have antibodies to shellfish. Latino children had the greatest increase in food allergies, but this may be due to greater awareness.
The most common food allergies are to proteins in cow's milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts. Peanuts and tree nuts are the leading cause of severe food allergic reactions. Luckily, many children outgrow allergies to milk and eggs. But severe allergies to foods like peanuts, some fish and shrimp can last all their lives.
Raising a child with food allergies adds even more expense and effort to your role as parents. Later this year, an expert panel of the National Institute of Allergy and Infectious Diseases will provide guidelines defining food allergies and giving criteria for diagnosis and management.
Hopefully, this will make your life just a little easier.
The information provided in this article is not intended to substitute for the advice of a medical doctor.