Parasites are micro-organisms which live in the intestines. Some cause symptoms while others can live for long periods in the bowel without causing symptoms or requiring treatment. However, the long term presence of parasites may contribute to the development of food allergies. Some intestinal parasites can cause symptoms such as loose foul-smelling stools, diarrhea, mucous in stools, abdominal cramps and gas. These symptoms may last for weeks and return several times a year. Other parasites are nearly harmless (at least in small quantities) and often don't cause symptoms. In North America and Europe, parasites rarely cause serious complications. The incidence of parasite infection is both overestimated and underestimated, depending on who you are listening to. If you have symptoms suggesting their presence, you should be carefully and even repeatedly tested, if necessary.

If you have parasites, you can reduce the likelihood of passing them on to others by carefully washing your hands after having bowel movements and cleaning the genital area before having sex.