I have been taking acidophilus for many, many years. I take it to increase the amount of good bacteria in my system, as it aids in the reduction of occasional yeast overgrowth I may experience. Never have I experienced any ill effects of this wonderful supplement. Acidophilus is good bacteria. I believe anything in moderation is safe. I have been taking supplements for over 20 years, so I'm knowledgeable of many. Acidophilus is especially helpful in conjunction with traditional medicines - especially antibiotics. Since antibiotics destroy all bacteria (good as well as bad) acidophilus replaces the good bacteria that antibiotics destroy. If ever I take antibiotics (which is extremely rare...I increase my garlic instead) I'd take acidophilus 1-2 hrs following my antibiotic. I hope this gives you the confidence to administer acidophilus without worry.