Hi & Welcome. thanks for your concerns. Keflex (Cephalexin) is a first generation cephalosporin antibiotic commonly prescribed to treat susceptible bacterial infections including upper respiratory infections, ear infections, skin infections, and urinary tract infections. Its common side effects include diarrhea, abdominal pain, rash and allergy. Although less common however it has been implicated in triggering seizures. He should stop taking Keflex and consult his treating doctor for an alternate effective antibiotic and also to take anticonvulsant depending upon the situation. Hope this answers.