Participants will have eight small blisters raised on the forearm using a gentle suction device. The top of the blisters will be removed with scissors and a plastic template will be placed over the blisters. The wells of the template will be filled with a salt solution or a mixture of the subject s serum (fluid part of the blood without cells) and a salt solution. Some blisters may be covered with coverslips a small round piece of very thin sterilized glass before adding the fluid. Blister fluid will be removed from the wells at 3, 5, 8, and 24 hours with a syringe and analyzed for inflammatory mediators. A scab will form over the blisters and fall off in about 2 weeks.