There are few greater feelings than laughing so hard that you cry.
Despite the seeming antithesis between the emotions of joy and sorrow, the two often produce the same bodily operation. Ancient Egyptian and Hippocratic physicians believed tears were a purging of toxin accumulation in the body. We know today that emotional tears contain an endorphin called enkephalin; an opiod peptide. Crying can be brought about by pain, but it is also a natural pain killer.