DNA Repair Activity in the Skin of Day and Night Shift Workers

Inclusion Criteria: * Male/Female * Fair skin (Fitzpatrick types I and II) * Age 18 to 40 * Able to comprehend procedures/risks * Primarily work and are awake during normal daylight hours (6 am to 6 pm), or primarily work and are awake during night shifts hours (between the hours of 6 pm and 6 am) or may work a mixture of these shifts over the past 3 months. Rotating shifts will be categorized based on the majority of hours worked on average during the last 3 months. Able to fill out a 3-month calendar of work schedule. Exclusion Criteria: * Known photosensitivity * Currently on photosensitizing medications * Diabetes Mellitus * On any hormonal agents (e.g., birth control pills) * History of abnormal scarring * History of skin infections * History of skin cancers * History of sleep disorders such as sleep apnea or insomnia * Known allergy to lidocaine local anesthetic * Pregnancy or nursing * Other serious health issues