Caucasian male and female participants age 18 years of age and older will be enrolled in this study if they have known birch or peanut allergies or known to be non-atopic. Participants will undergo skin testing to confirm their allergies if not completed in the last 12 months. Medications and medical history will be captured with a focus on atopic disorders. Participants will undergo birch and peanut patch testing to assess penetration and if potential correlation exists with filaggrin genotyping and phenotyping. Blood samples will be drawn from participants and DNA isolated for genotyping of null mutations in filaggrin.