Fig 6. Illustration of the sweat collection procedure.

Briefly, the whole back was wiped with tap water (STEP 1), and a drape with a 15×20 cm square hole was applied (STEP 2). Petrolatum was applied to the area in the hole (STEP 3). The bottom of the drape was folded up to create a pocket for fluid collection as subjects bathed in a sauna at 80°C (STEP 4). The sweat that pooled in the drape was collected with a syringe and filtered with a cartridge-type 0.22-μm filter.