This study will explore potential links between atopic dermatitis and food allergy. This information will be useful to determine atopic dermatitis and food allergy share unique biochemical or genetic identifiers useful for diagnosing and treatments in the future.

This is a mechanistic study consisting of obtaining blood and skin samples from participants at baseline. Individuals may also undergo a clinically indicated oral food challenge and have blood and skin samples collected at various times during the oral food challenge. This study will create a molecular map of the pathology of atopic dermatitis and food allergy. This information will be deployed to evaluate the hypothesis that atopic dermatitis and food allergy share unique genetic transcriptional signals in which the study team can then further analyze pathological pathways and cell types.

This study will be funded by the National Institute of Health. Once the funds are received, the registration will be updated with this information.

Food allergy-only group Inclusion Criteria:

• Have a known history of food anaphylaxis to peanut, tree nut, egg, milk, or sesame confirmed by an allergist.
• Have had skin and blood food allergy testing to the food allergen in question within the past 6 months. Meet the 80% likelihood positive predictive value threshold for allergy based on at least 1 of either the skin or blood immunoglobulin E (IgE) tests per current literature corrected for age. See protocol for more details.
• No history of atopic dermatitis

Food allergy plus atopic dermatitis group Inclusion Criteria:

- Meet the "food allergy only group" inclusion criteria except this group must also have atopic dermatitis.

Atopic dermatitis without food allergy Inclusion Criteria:

• Have a present diagnosis of atopic dermatitis by an allergist and/or dermatologist.
• Have no history of food allergy, past or present.

Control Group Inclusion Criteria:

- No history of food allergy or atopic dermatitis, past or present.

Exclusion Criteria for all groups:

• People younger than age 10 or older than age 55
• Any active cardiovascular disease, cancer, pulmonary disease except well-controlled asthma, or other condition that would preclude an OFC otherwise. Mild conditions that would not preclude an OFC are allowed (i.e., controlled hypertension or a surgically removed skin cancer that is resolved would not be exclusionary for this study, for example).
• Any medication use that cannot be stopped temporarily for the OFC that would interfere with the OFC result. Medications in this category include antihistamines (first or second generation) within 1 week.
• Any skin condition aside from atopic dermatitis per inclusion criteria groups that might impact the study, including such conditions as autoimmune skin conditions (such as psoriasis), congenital ichthyoses, hyper-IgE syndromes.
• Any recent change (within 6 months) of starting or stopping a biologic medication, such as dupilumab, tezepelumab, or others that might interfere with atopic dermatitis or food allergy.
• Any past or present history of oral immunotherapy (OIT) for any food allergen.
• Pregnancy - females of childbearing age will be asked and self-report pregnancy status.