There are some sayings about sleeping with we hair. The most common and popular sayings about it are this action will lead to cold or bad eye sight, even blindness. Yet it seems that there is no reliable evidence or study about the two theories, which are suggested to be mythical by most sources. So far, there is no direct correlation has been found between sleeping with wet hair and blindness. Yet you need to know it is not good to sleep with wet hair. Sleeping with wet hair will cause buildup of fungus on pillow. We spend one third of our life time on pillow, thus we are exposed to various fungi, which could cause many kinds of respiratory conditions. Fungi could build up on our scalp, which will cause too much dandruff. When I was little, my mother also told me that sleeping with wet hair will make me headache. Anyway sleeping with wet hair is harmful to our health. You 'd better not to do so.
