Chronically photodamaged skin is visually characterized by dryness, wrinkles, brown spots, leathery appearance, etc. While photodamage leaves the skin's surface visibly changed, the skin's unseen immune system may also be permanently altered as a result of the exposure, making it more likely to develop a variety of skin cancers and infections.~This study will aim to evaluate the lasting changes that lifetime UV exposure causes to the different components of the skin's immune system in chronically sun damaged skin (forearms) compared to sun-protected skin (buttocks). Investigators will compare the cellular responses to stimulation of the skin's innate immune system, the skin's adaptive immune system, and the skin's hypersensitivity responses between these two sites.~In order to stimulate the different arms of the immune system, investigators will be using the following interventions: an intradermal injection of Candida Albicans antigen, an intradermal injection of histamine phosphate, a topical application of imiquimod 5% cream, and a tape stripping procedure with adhesive tape. Skin testing with the C. albicans antigen is a useful procedure for measuring the capacity of a person to manifest a delayed-type hypersensitivity response and is commonly used in clinical settings to evaluate cellular immunity. Similarly, histamine phosphate is frequently used as a positive control in clinical tests to assess type I Immunoglobulin E (IgE)-mediated hypersensitivity reactions. Imiquimod 5% cream is a direct stimulator of toll-like receptor (TLR) 7, a key component of the innate immune response with downstream signaling effects involving the adaptive immune response. It is FDA-approved for the treatment superficial basal cell carcinomas, actinic keratoses, and genital warts. Finally, tape stripping is a validated procedure used to remove superficial layers of the epidermis in clinical study environments.~Objective: This is a mechanism of action pilot study designed to characterize the molecular nature of the local innate and adaptive immune response in chronically photodamaged skin (forearm) as compared to photoprotected skin (buttocks) using non-photodamaged individuals (forearms and buttocks) as a control.~Population: Adult subjects with or without photodamage will be entered into the study at the University of Michigan.~Procedures: study interventions (tape stripping, candida albicans and histamine phosphate injections, imiquimod 5% cream application), photography, Chroma Meter reading, biopsies, skin assessment
Chronically photodamaged skin is visually characterized by dryness, wrinkles, brown spots, leathery appearance, etc. This happens as a result of excessive exposure to UV light from the sun. While the sun's exposure leaves the skin's surface visibly changed, the skin's unseen immune system may also be permanently altered as a result of the exposure, making it more likely to develop a variety of skin cancers and infections. This study will examine the lasting changes in the immune system of the skin caused by UV exposure. Investigators will stimulate different aspects of the skin's immune system by giving an injection of Candida Albicans (CANDIN®) and histamine phosphate (HISTATROL®), topical applications of imiquimod 5% cream (ALDARA®) and performing a tape stripping procedure with adhesive tape. The use of Candida Albicans (CANDIN®), histamine phosphate (HISTATROL®), and tape stripping are common procedures in clinical settings to stimulate skin desired skin responses. Imiquimod 5% cream (ALDARA®) is an FDA-approved drug for the treatment of basal cell carcinomas, actinic keratoses and genital warts. Investigators will compare the reaction of the skin's immune system on a cellular level from skin normally exposed to the sun exposure to an area normally hidden from sun exposure.