Although sweat is mostly water, it also contains oils and fats. As perspiration evaporates from your garments, it leaves behind salt, which may cause stiffness on your fabric. When the residue encounters heat, it oxidizes, leaving a white powder substance. Over time, these stains can become much more noticeable. Often, garments without noticeable perspiration marks will develop noticeable stains after going through the cleaning process. By pre-treating your garments, however, you can minimize the risks of stains becoming set in before you get them to the professionals for a thorough cleaning. If you notice heavy perspiration stains on a garment, flush the stained area with hot water or the steam setting on your iron. Then add a small amount of laundry detergent to the stain. Work the detergent into the stained area by tapping—not scrubbing. Flush the area with water or steam or water again and repeat as needed. In addition to pre-treating stains, you can also prolong the life of your garments by considering the deodorant or anti-perspirant that you use.