Two years after outgrowing a peanut allergy, Holly Sweenie finally took a peanut butter and jelly sandwich to school.
"It took me a long time to get up the courage to pack one," said Sweenie's mom, Susan, of Canton, Mass. "I assumed allergies were something she'd always have."
Happily, allergies aren't always life sentences. But it can be difficult to tell when children have aged out of an allergy, and if they have, whether eating those previously forbidden foods should be part of the treatment.
A whopping 80 percent of children will lose their sensitivity to milk, egg, wheat and soy allergies by adulthood, said Dr. Robert Wood, director of pediatric allergy and immunology at Johns Hopkins Children's Center and a prolific allergy researcher. Even life-threatening peanut and tree nut allergies can recede; over time, 20 percent of children will lose their sensitivity to peanuts and 10 percent will be able to tolerate tree nuts.
Some children with respiratory allergies such as hay fever, meanwhile, can improve and even "outgrow" the allergy as they mature, usually around puberty, said Dr. Michael Welch, co-director of the Allergy and Asthma Medical Group and Research Center in San Diego. "Often, the skin test reactivity stays the same, but the symptoms of a sizable number of children greatly improve with age," he said.
Still, allergy rates continue to rise -- they've doubled since the 1970s -- and defy easy explanation. Although some people have a genetic predisposition, scientists don't know what causes allergies.
One popular theory is the "hygiene hypothesis," which Minneapolis allergy and asthma specialist Dr. Allan Stillerman describes as "a belief that your immune system in the olden ages tended to be boosted to fight infections, but our increasingly hygienic society has left the immune system unstimulated in its ability to fight infectious agents."
Stillerman added, though, that allergy rates have been overstated.
"There's so much misdiagnosis," he said. "A quarter of Americans believe they have food allergies. But it's only 4 percent for adults, and for children at the heart of the problem who are 1 to 2 years old, it's 6 to 8 percent."
Still searching for answers
Scientists still don't know why children can overcome sensitivity to certain foods but not others.
Treatment generally involves avoidance; the hope is that the immune system will gradually forget about the allergen. But paradoxically, "exposure may help someone with allergies become more tolerant of small amounts," Wood said.
For patients with environmental allergies, allergy pills or shots, also called immunotherapy, are used to help with desensitization. It's thought that immunotherapy gradually retrains the immune system to completely disregard or tolerate the allergens that cause the reactions.
For food allergies, however, immunotherapy isn't quite ready for prime time. Preliminary data show that giving children with milk allergies increasingly high doses of milk over time might ease or help them overcome the allergy, but researchers warn that it should never be tried at home. Feeding peanuts to someone with peanut allergies, for example, can result in life-threatening anaphylactic shock.
If a child has outgrown the peanut allergy, it might be a different story. Some research shows that reintroducing peanuts after a child can tolerate them might help prevent a recurrence. Although the mechanism isn't known, Wood's work has shown that children who outgrew peanut allergies and then ate peanut butter, shelled peanuts or peanut candy at least once a month had a lower risk of recurrence than those who didn't.
Still, Wood recommends that children who do eat concentrated peanut products carry epinephrine injections for at least a year after passing a food challenge, an allergy test in which the child eats small amounts of the suspected allergen in the doctor's office.
Some happy endings
Stillerman lauded Woods' study and said the findings were similar to what his work with the Twin Cities-based Allergy & Asthma Specialists has found.
Among his patients are Zachary and Paige Smith of Andover. The twins, now 3 1/2, had allergies to eggs, milk, tree nuts, soy and wheat, diagnosed by Stillerman when they were 1 year old. (A pediatrician and a skin specialist had not found their eczema and other problems to be allergy-related, said their mother, Jennifer Smith.)
"So once we found out, we ceased all of those things and my son's skin cleared up within a week or two," Jennifer Smith said.
About a year ago, the twins took part in a "food challenge" at Children's Hospital, where they consumed increasingly larger doses of dried Cream of Wheat mixed with applesauce. They encountered no problems.
After subsequent testing, Smith has reintroduced milk to her kids' diets, and she is hopeful that the egg allergy might go away.
"We're just happy that we can give them bread and milk and cheese and yogurt," Smith said.
Another Stillerman patient, Emma McFarlane of Anoka, developed hives after eating peanuts when she was 18 months old. Skin tests showed she was "extremely allergic to peanuts," said her mother, Christie, and "over the next four years, we were very cautious about avoiding peanuts."
Last summer the McFarlanes had Emma's allergy checked during her annual physical, and she passed skin, blood and eating tests. Christie McFarlane said she was "so happy, I wanted to jump out of my skin."
"There's just so much pressure," McFarlane said. "Every party they go to, every picnic they go to, you have to watch out. And it makes them feel singled out by it.
"It's just a huge relief for all of us."
Staff writer Bill Ward contributed to this report.