The Yale Allergy & Immunology Contact Dermatitis Program serves patients affected by one of the most common causes of both personal and occupational allergic skin diseases: allergic contact dermatitis (ACD). ACD is an immune reaction that typically causes a rash in response to a substance in personal care products, medications, or even diet. Other potential allergic sources include occupational exposures and biomedical implants, all of which can result in chronic and sometimes debilitating symptoms. Identification of the offending allergen is key to the rapid diagnosis and resolution of ACD. Patch testing, in which allergens are placed in chambers held in place with adhesive patches on the back, is the gold standard for the diagnosis of ACD. The testing usually takes place during three visits over the course of a week after the initial consultation is completed. At the first visit, the patches are placed, and a second visit occurs 48 hours later for patch removal. Between 72-96 hours after the initial patch placement, a third visit occurs with a final diagnosis and a physician follow-up. Occasionally, a fourth visit is needed for delayed reads of certain allergens. We have the ability to test to multiple extended allergen series, medications, occupational and healthcare-specific substances, as well as some product brought in by patients. We take a personalized approach to the diagnosis and care of patients with contact dermatitis. From the initial consultation and testing phase, where potential allergens will be determined, a custom patch test prescription is prepared, and, ultimately, allergen identification/avoidance strategies and a treatment plan are formulated.