skin or soft tissue infection
"I was prescribed this as a precaution because I had a mole removed, however I had the worst experience. 
I don't know if I had food poisoning during the first night of taking it, or if it was entirely the cephalexin, but I had a 12 hour episode of vomiting and diarrhea, after that I was for an entire week with nausea and evidently sick (couldn't eat anything different than BRAT diet). I decided to stop taking cephalexin and in 12 hours I was MUCH better. 
My doctor said that since we are all different, some antibiotics might not work at all for some of us. This is the first time in my life I had a bad experience with an antibiotic."