AbstractBackgroundThe reasons for the apparent increased risk of skin cancer in Celts are unclear, but it is possible that Celts possess more risk factors than non‐Celts.AimsTo determine whether Celts differ from non‐Celts with respect of cutaneous response to UVR, and tests of cell mediated immunity.MethodsThe MED of UVB, degree of clinical photodamage, pigmentation, numbers of peripheral blood T‐lymphocyte sub‐sets, and response to a battery of infra‐dermal antigens were determined in 18 Celts with a history of BCC and 18 age, sex, and skin type matched non‐Celts with a history of BCC. Each was then exposed to 2MED, and biopsies taken of irradiated and non‐irradiated sites at 24 h.ResultsCelts tended to have a thinner epidermis than the non‐Celts. Following irradiation the epidermal thymidine labelling index in Celts had almost doubled, whereas in non‐Celts it fell slightly. We found no differences in photodamage, freckling, pigmentation, MED, the erythema response to 2MED, numbers of peripheral T‐lymphocytes, or tests of cell mediated immunity.SummaryThe tendency of Celts to a thinner epidermis and an increased epidermal labelling index following UV irradiation may be a reflection of an increased susceptibility to skin damage fo