Lactobacilli are bacteria that normally live in the human small intestine and vagina. Lactobacillus acidophilus is generally considered to be beneficial because it produces vitamin K, lactase, and anti-microbial substances such as acidolin, acidolphilin, lactocidin, and bacteriocin. Multiple human trials report benefits of L. acidophilus for bacterial vaginosis. Other medicinal uses of L. acidophilus are not sufficiently studied to form clear conclusions.

The term "probiotic" is used to describe organisms that are used medicinally, including bacteria such as L. acidophilus and yeast such as Saccharomyces boulardii.

Although generally believed to be safe with few side effects, oral L. acidophilus should be avoided in people with intestinal damage, a weakened immune system, or with overgrowth of intestinal bacteria.

Acidophilus, Acidophilus Extra Strength®, acidophilus milk, Actimel®, Bacid®, Cultura®, DDS-Acidophilus, Endolac®, Enpac®, Fermalac® (Canadian), Florajen®, fresh poi, Gynoflor®, Infloran®, Kala®, Kyo-Dophilus®, L-92, L. acidophilus, L. acidophilus OLL2769, L. acidophilus milk, L. acidophilus yogurt, Lacteol Fort®, lactic acid-producing bacteria (LAB), Lactinex®, Lactobacillaceae (family), lactobacilli, lactobacillus, Lactobacillus acidophilus 145, Lactobacillus acidophilus DDS-1, Lactobacillus acidophilus LA 02, Lactobacillus acidophilus La5, Lactobacillus acidophilus L-92, Lactobacillus acidophilus NCFM, Lactobacillus acidophilus NCK56, Lactobacillus acidophilus strain 27L, Lactobacillus acidophilus strain LB (LaLB), Lacto Bacillus, MoreDophilus®, Narine®, poi, Probiata®, Pro-Bionate®, probiotic, sour poi, Superdophilus®, yogurt.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Bacterial vaginosis (Grade: B)
Multiple human studies report that

Allergy treatment (Japanese cedar pollen) (Grade: C)
A small study was conducted to evaluate the effects of

Asthma (Grade: C)
There is limited research in this area, with unclear results.

Diarrhea prevention (Grade: C)
A small amount of human research suggests that

Diarrhea treatment (children) (Grade: C)
A small amount of research in children, using different forms of acidophilus, reports no improvement in diarrhea. Future studies should use a viable

Hepatic encephalopathy (confused thinking due to liver disorders) (Grade: C)
There is limited study in this area, with mixed results.

High cholesterol (Grade: C)
There is conflicting information from several human studies regarding the effects of

Irritable bowel syndrome (Grade: C)
Human studies report mixed results in the improvement of bowel symptoms after taking

Lactose intolerance (Grade: C)
There is conflicting information from several human studies as to whether using

Necrotizing enterocolitis prevention in infants (Grade: C)
One human study using

Vaginal candidiasis (yeast infection) (Grade: C)
taken by mouth or as a vaginal suppository has not been adequately assessed for the prevention or treatment of vaginal yeast infections. More research is needed in this area a before a conclusion can be drawn.