Probiotics are microorganisms, such as bacteria and yeast, found naturally in the intestines, according to WebMD. The human intestinal tract contains more than 500 types of bacteria that help digest food. The American Gastroenterological Association indicates the two most common types of commercially available probiotics include various strains of Lactobacillus and Bifidobacterium.
Although research into the effects of probiotics is still underway, WebMD explains probiotics may help keep the intestines in balance to digest food properly as good bacteria in the gastrointestinal tract is sometimes killed by infections, antibiotics or damage to the intestinal lining. Probiotics may treat diarrhea, ulcerative colitis, inflammation of the intestines and eczema related to cow's milk allergies. Probiotics may also improve immune system function because they help create proper immune responses in the body. The AGA reveals probiotics help fight irritable bowel syndrome, inflammatory bowel disease, infectious diarrhea and allergies.
WebMD states foods such as yogurt and cheese have contained probiotic bacteria for centuries, and these microorganisms cause few side effects. Probiotics are generally thought to be safe for human consumption, according to the AGA. Dietary supplements with probiotics are not regulated by the FDA. People who take supplements should consult a doctor, use well-established manufacturers, follow the label's instructions and call the manufacturer for more information.
WebMD states people with weakened immune systems or serious illnesses should avoid probiotics. One study found patients with severe pancreatitis had a higher risk of death after consuming probiotics.