You can sleep in a toupee as long as you feel comfortable. However, some people avoid sleeping in them to prevent damaging the strands. In most cases, sleeping in a toupee may cause tangles and frizz. As a result, the hair might become loose and shed, thus reducing its lifespan. But you can avoid such problems by sleeping on a silk or satin pillowcase. This reduces friction between your hair and the pillow, thus, lessening tangles and frizz.