The side effects of cephalexin are as follows. The first aspect is the common gastrointestinal symptoms, such as patients can have nausea, vomiting, acid reflux, belching, bloating, abdominal pain, diarrhea, constipation, and mucus stools. The second aspect is allergic reaction, patients can have rash, hives and itching of local blood vessels. The third aspect is neurological symptoms, patients may experience drowsiness, delirium, euphoria, and coma. The fourth aspect may be hematologic, such as transient leukocyte or platelet depression. The fifth aspect is rare, there is a transient impairment of liver and kidney function.