Normal volunteers and patients with acute helminth (a type of parasite) infections aged 18 years older may be eligible for this study. Following a medical history and physical exam, participants will undergo suction blistering to provide cells needed for study. A suction blister device is attached to the skin of the thigh. A heating element in the device heats the skin to speed blister formation. (This will feel only a slightly warm.) The device is removed after about two hours, when the blisters have formed. The blister tops are removed with sterile scissors. The blistered areas are then treated with special dressings to promote healing and the participant is discharged with further wound care instructions. A small amount of blood (around four tablespoons) may be drawn to compare chemicals in the blood with chemicals in the blister fluid. Participants will be contacted by telephone over the next 72 hours to check on healing. Further follow-up will occur by phone at 6 months and 1 year.