moonlit night

In folklore, moonlight sometimes has a harmful influence. For example, sleeping in the light of a full moon on certain nights was said to transform a person into a werewolf. The light of the moon was thought to worsen the symptoms of lunatics, and to sleep in moonlight could make one blind, or mad. Nyctalopia (night blindness caused by a lack of vitamin A), was thought to be caused by sleeping in moonlight in the tropics. [Wikipedia]