SN instructed patient and/or caregiver that Cephalexin is an antibiotic that can treat a number of bacterial infections. Common adverse effects of Cefalexin, like other oral cephalosporins, are gastrointestinal , disturbances and hypersensitivity reactions. Gastrointestinal disturbances include nausea, vomiting, and diarrhea. Hypersensitivity reactions include skin rashes, urticaria, fever, and anaphylaxis. Pseudomembranous colitis has been reported with use of Cefalexin. Signs and symptoms of an allergic reaction include rash, itching, swelling, trouble breathing, or red, blistered, swollen, or peeling skin.