What are the possible side effects of taking acidophilus?

Acidophilus is considered a generally safe supplement with very few side effects when taken in appropriate doses, according to Mayo Clinic. Children under 6 months of age should not take acidophilus, as it has been linked to an increased sensitivity to cow's milk.

Although acidophilus does not frequently cause side effects, the most common side effect is gas, according to Mayo Clinic. In some extreme cases, certain strains of acidophilus have been linked to infection, but this is very rare and generally occurs in individuals with weak immune systems. Individuals with stomach issues should only take acidophilus in low doses due to a slight chance of irritation.