A Sensitive Child

From cradle cap to diaper rash, very young children are prone to several types of der-matitis. Until recently, though, allergic contact dermatitis was considered uncommon among this age group. Conventional wisdom held that young children's immune systems were too immature to be sensitized to allergens encountered through skin exposure. But new research casts doubt on conventional wisdom. In a study published in the January 2000 online version of Pediatrics at http://www.pedi-atrics.org/, researchers from the University of Colorado Health Sciences Center in Denver demonstrate sensitization at an early age. Their study is unique in that it focuses exclusively on children younger than five years. At any age, dermatitis symptoms include skin reddening, scaliness, blistering , ulceration, and itching. With contact dermatitis, symptoms follow skin exposure to an irritant (which can affect anyone, regardless of immunological status) or an allergen (which only affects sensitized individuals). Sensitization occurs when an allergen seeps below the skin surface and is processed by Langerhans cells-immune system cells that carry an allergen fragment , or antigen, to T lymphocytes in the lymph nodes. When this occurs, cells called memory T lymphocytes are produced. These cells release cytokines that attract inflammatory cells, triggering der-matitis. "I think the reason why many people think that the risk of contact sensitiza-tion in children is lower than in adults has to do with the fact that people have always thought that the immune system of younger children wasn't capable of reacting to these agents," says Bernard A. Cohen, director of pediatric dermatology at the Johns Hopkins Children's Center in Baltimore, Maryland. `And the evidence doesn't support that at all." The team of Colorado researchers, led by pediatrician Anna L. Bruckner, recruited 95 patients between six months and five years of age who did not have dermatitis. Each child had strips with 24 separate allergen patches affixed to his or her upper back, and the parents were instructed to remove the strips 48 hours later. Two to three days afterwards, the researchers Early ouches. New research shows that children may experience early allergic sensitization from ex substances such as thimerosal (a component of vaccines) and nickel (found in buckles and snaps on clo examined the children. Of the 85 children completing the study, nearly 25% exhibited sensitivity to one or more allergens. Nickel and thimerosal (a preservative used in vaccines) caused the most sensitization reactions, with 1 1 and 8 reactions, respectively. The …