Peanut allergy is one of the most common allergies that can become fatal or near-fatal. In sensitive individuals, the nuts can trigger a potentially life-threatening swelling of the lips and airways, accompanied by a dangerous drop in blood pressure.

Experts estimate that 1% of the population is allergic to peanuts--about 3 million people in the US.

Researchers at Mount Sinai School of Medicine in New York City routinely follow the peanut allergies of children. In the current analysis, published in the November 7th issue of The New England Journal of Medicine (news - web sites), lead author Dr. Scott Sicherer and colleagues report on three children who had positive allergic reactions and skin prick tests to peanuts between the ages of 1 and 4. The children tested negative for peanut allergy at the ages of 5, 8 and 9, respectively, but had recurrence of peanut allergy symptoms roughly a year after testing negative.

"This outcome had been previously unheard of in children with peanut allergy," Sicherer said in an interview with Reuters Health. "Why these children became tolerant and then intolerant of peanuts we do not know," he noted.

"The bottom line message is that this study takes earlier findings a step further in that children who are medically shown to become peanut tolerant may redevelop their peanut allergy," Sicherer explained.

Sicherer also recommended that physicians specializing in allergy may wish to take a "special measure of caution" when counseling parents with children who outgrow their peanut allergy.

"It seems prudent to maintain access to emergency medications, such as self-injectable epinephrine, for patients with resolved peanut allergy until peanuts are routinely tolerated in relevant quantities for at least one or two years," the authors conclude.

SOURCE: The New England Journal of Medicine 2002;347:1535-1536.