The primary goal of the study is to investigate the impact of a common genetic polymorphism in a histamine detoxification enzyme that may well have a common role in regulating the expression of atopic dermatitis (AD) and other related atopic diseases in children.

Atopic dermatitis (AD) is a common condition in the pediatric population, affecting an estimated 15% of all children greater than 18 months of age in the United States. It is now recognized that AD is a disease of significant heterogeneity with respect to both disease severity and response to conventional pharmacologic therapies. With the recognition of this variability comes the understanding that, as with many other allergic disease, there exist many specific disease phenotypes that ultimately govern response to pharmacologic intervention. The characterization of these unique phenotypes and their associated biologic mediators is therefore of critical therapeutic importance in the development of disease and patient-specific treatment strategies.

The long term objective of this research is to explore the effects of genetic, environmental and developmental influences on the primary determinants of histamine action in atopic children and to identify potential histamine "haplotypes" that may be predictive of disease severity, progression and/or response to therapy.

The primary hypothesis is the presence of HNMT T314 allele and /or slow acetylation genotype is associated with childhood atopic dermatitis.

Inclusion Criteria:

• Caucasian, Hispanic and African American children ages 6 months to 5 years with a diagnosis of atopic dermatitis within the last 12 months will constitute the candidate pool for enrollment into the study group. The diagnosis of atopic dermatitis will be determined by the presence of at least 3 major diagnostic features (i.e., pruritis, rash,relapsing-remitting presentation, family history or atopy) in addition to at least 3 minor features (including but not limited to xerosis, elevated serum IgE, ocular involvement, food allergy). Healthy Caucasian, Hispanic and African American children within the same age range will comprise the pool for enrollment into the control group.

Exclusion Criteria:

• Any child with atopic dermatitis who has a documented history of asthma or bronchospasm or who is currently receiving treatment for either of these conditions will be excluded. Any control subject who has asthma or positive family history of allergy or atopic disease in a first-degree relative (biological mother, father or siblings) will also be ineligible for enrollment.

• American College of Clinical Pharmacy
• Pediatric Pharmacology Research Unit (PPRU)
• Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)