Some side effects of probiotics include gas, bloating, upset stomach and diarrhea. These symptoms typically do not last more than a couple of days after an individual starts using them. Probiotics may cause an allergic reaction to happen, and if that occurs, consult a doctor, states WebMD.
Probiotics are a dietary supplement, according to Drugs.com. The most common probiotics belong in the lactobacillus group and are typically found fermented foods like yogurt, states WebMD. Certain strains of lactobacillus may help individuals who are unable to digest lactose and may also help with diarrhea. Probiotics may also come from the bifidobacterium group, and these may help the symptoms of irritable bowel syndrome.