Even if your bath towel doesn't smell stale after you've used it more than once, it may be time to wash it. A bath towel is a breeding ground for bacteria once you've used it, making it a potential health concern after several uses between washings. Wash towels after three or four uses to keep them smelling their best and to keep them as germ-free as possible.
When you dry off after a shower, that towel absorbs dead skin cells off your body along with the water. These cells serve as food for the bacteria that thrive within the damp fibers of a towel. The bacteria may not be a big deal, but if you have an open wound, they could cause an infection if you use the towel again.
Keep track of how often you use the bath towel, replacing it after three to five days. If you take more than one bath or shower in a day, replace it even sooner -- even after each use; otherwise, the towel may not be dry when you use it. If the towel smells less than fresh before five days have passed, swap it out for a fresh one.
Towels must be able to dry completely -- and somewhat quickly -- to prevent damp, musty odors. Hang them on a towel rack or hook so they are exposed to as much air as possible. Open the bathroom after a shower or bath to release the moisture, or turn on an exhaust fan. Keeping the towels in a damp or humid environment or leaving them in a heap on the floor doesn't allow them to dry out completely, which leads to stale odors or even mildew. Be sure to rinse off thoroughly before using the towel as well; otherwise, soap or shampoo soil the towel and transfer back onto your body the next time you use the towel.
Hand towels in the bathroom should be swapped out at least as often as the bath towels, or potentially more if multiple people use them -- especially young children that may not have established sufficient hygiene skills yet. Swap the washcloth out for a fresh one after every use or two, as it gets far dirtier and wetter than a bath towel, making it even more of a breeding ground for germs and bacteria or even mildew and viruses.
To return towels and washcloths to a fresh-smelling state once again, wash them in hot water along with your usual laundry detergent. Add a cup of vinegar to the final rinse to help remove soap residues and odors. Dry the towels thoroughly in the dryer or on a clothesline before folding them to prevent mildew or stale smells. Skip fabric softeners and dryer sheets which leave behind a residue that traps odors into the towels.