I was prescribed Cephalexin for an infection on my leg. After a couple days I had a hard time breathing, felt light headed and like my airway was partially closed off. I was very tired & sick to my stomach. I didn't hardly eat for a couple days because I just wasn't hungry. I skipped my pill at bed time to see what would happen and by the time I woke up I was definitely feeling better, so I didn't finish out the prescription. The infection did go away though.