I personally know it kills yeast. My son gets an occasional yeast rash in his unmentionable area due to not bathing often when he is at his dads, and I will spray him with CS, and he feels relief from itching almost right away. Also I believe i have seen that as one of the things it helps. My daughter has spina bifida, and her toes are prone to fungus because of the lack of movement so I spray her feet and the don't have that funny smell anymore. I would definitely guve your freind some. It will work, just have him spray it on his feet a few times a day until it goes away then if he's prone to it, just have hime spray like after his shower or in the morning before he puts his shoes on. Hope this helps some