Acidophilus (Lactobacillus acidophilus), a bacterium found in the mouth, intestine and vagina, is used as a probiotic. Probiotics are good bacteria that are either the same as or very similar to the bacteria that are already in your body. Each type of probiotic supplement — and each strain of each type — can work in different ways.

As a supplement, acidophilus is available as capsules, tablets, wafers, powders and a vaginal suppository. In addition to use as a supplement, acidophilus is found in some dairy products, such as yogurt, and is commercially added to many foods.

People commonly take acidophilus to treat a type of vaginal inflammation (bacterial vaginosis) and digestive disorders, as well as to promote the growth of good bacteria.


Research on acidophilus use for specific conditions shows:

  • Bacterial vaginosis. Oral use of acidophilus and use of vaginal acidophilus suppositories or application of yogurt containing acidophilus to the vagina has been shown to be effective in treating this type of vaginal inflammation.
  • Lung infections. Acidophilus might play a role in reducing the number and severity of respiratory infections children experience.
  • Certain types of diarrhea. When taken with antibiotics, a combination of acidophilus and other specific forms of lactobacillus might reduce diarrhea, bloating and cramps caused by a bacterium that can cause symptoms ranging from diarrhea to life-threatening inflammation of the colon (C. difficile infection). The probiotic formulation might also reduce the occurrence of antibiotic-associated diarrhea and C. difficile infection in people who are hospitalized.
  • Eczema. Oral use of acidophilus during pregnancy, by breast-feeding mothers and by infants appears to reduce the occurrence of eczema (atopic dermatitis) in infants and young children.

Acidophilus products might contain significant differences in composition, which could cause varying results.

Our take

Green light: Generally safe

Generally safe

There’s growing interest in probiotics such as acidophilus. While more research is needed there appears to be little harm in taking acidophilus. However, a balanced diet, including fermented foods such as kefir, might provide you with sufficient “good” bacteria.

Safety and side effects

Possible side effects from acidophilus include:

  • Constipation
  • Gas
  • Bloating
  • Increased thirst

If you’re immunocompromised, consider talking to your doctor before taking a product such as acidophilus that contains live bacteria.

If you’re lactose intolerant, be aware that some acidophilus products might contain lactose.


There are no known significant interactions for acidophilus.

Nov. 18, 2020