I was taking 1 mg of Melatonin for about 3 months for sleep after my Bro died & it worked so well for sleep. Suddenly I started having acute diarrhea. I couldn't even go out. Tried Immodium, a special diet... you name it, I tried it. I didn't even think of Melatonin as the culprit as I had not had any side effects in 3 months of taking it nightly. My Doc did stool cultures,tests... nothing was wrong. I finally started looking on the Internet after 2 months of severe diarrhea & came across a support site where people were having the same as I was due to Melatonin. I stopped it & wthin 2 days the diarrhea was gone. I didn't take any for close to a year but 2 nights ago I had insomnia again & took half of a 1 mg Melatonin. In the morning I had a couple of bouts of diarrhea but I also was sneezing & had a very runny nose all day. Thought I was getting a cold. I did not take any Melatonin that night & in the morning my "cold" was miraculously gone! Sneezing & runny nose plus diarrhea are now listed as side effects of Melatonin on some sites. But only half of 1 mg causes this? Has anyone else experienced these side effects? My Doc had never heard of it. Just crazy! But when I stop the Melatonin I am fine. Anyone else?