Alena Machovcová

*University Hospital Motol, Prague Czech Republic* 

### **1. Introduction**

Contact allergy (CA), a pathologic response after (usually repeated) contact to environmental substances of low molecular weight occurring in a varying proportion of exposed persons, often results in clinical disease, allergic contact dermatitis (ACD), which can be disabling. CA is diagnosed by patch testing, a technique of controlled exposure of patients suspected to have ACD to a standardized set of substances frequently found to be the cause of ACD (Uter, 2004). ACD is an inflammatory reaction of the skin that follows percutaneous absorption of antigen from the skin surface and recruitment of previously sensitized, antigen-specific T lymphocytes into the skin (Rietschel & Fowler, 2001a). Although sensitivity to contact allergens occurs in 10-20% of the adult population, the exact incidence and prevalence of sensitization in children is unknown. ACD in children is not rare. The documented rates of ACD in children are on the increase (Militello et al., 2006; Goossens & Morren, 2006). Sensitization to contact allergens begins in infancy and continues to be more common in toddlers and young children. Infants, even neonates, may be sensitized (Fisher, 1994a; Bruckner et al., 2000). The rate of positive results may vary with referral patterns, selection criteria for patch testing, regional and social variations in allergens exposure and the allergen tested (Militello et al., 2006; Goossens & Morren, 2006; Wahlberg & Lindgerg, 2006).
