“The perspiration exuding from exertion of practice should be rubbed into the body (and not wiped), as by so doing the body becomes strong.”
Hatha Yoga Pradipika, Chapter 2 verse 13
Sweat is important product of vinyasa (breathing and movement system) and during the practice when we combine asanas with the breath and the movement the blood circulates freely in the entire body washing away pain and disease. S.K. Pattabhi Jois used to say that the blood boils. And when the blood boils all the poisons are burnt. This heated blood moves through internal organs and around the joints and brings out impurities with the sweat.
Sweat is a result of a very powerful detox process which occurs in the body during the practice. And when we rub the sweat back into the body we increase the amount of sweat and we make the detoxification process more effective. When we wipe the sweat during the practice we make our body cooler and more stiff so we prevent a strong purification process.
So during the practice do not wipe your sweat! Rub it back into exposed parts of your skin. Apart of mentioned above its an interesting to mention that since the water has a capacity to carry the energy and memory and if we wipe the sweat we drain the energy we generated during the practice. So if we rub the sweat back we push the energy back. It is also recommended not to take a shower at least 1,5 hours after practice.
May be its the time to develop right habits at your practice, start rubbing the sweat instead of wiping it!