Weeping releases a chemical that reduces sexual arousal in men. The chemical releases a signal that says they are not interested in romance at the moment, which men instinctively respond to by shutting down feelings of arousal. To be specific, this refers to deeply emotional tears, not those caused by getting something in the eye, or a moderately sad movie.
Typically, those arousal-killing chemicals are only released during full emotional weeping. Neuroscientist Noam Sobel of the Weizmann Institute of Science in Rehovot, Israel, put together an experiment to test this. Sobel collected jars of tears from women and dipped pads in them.
They placed the pads under men's noses and showed them pictures of women. The men smelling tears rated the faces as less attractive when compared to men who did not smell tears. To support it scientifically, their testosterone levels were measured, and, not surprisingly, they dropped.
Source: OMG Facts