many things can cause hives but the antibiotic he was taken. even if he recently finished it. is still high on the list of possibilities.
drug allergy-my husband was taking anitbiotics prescribed by a dentist for a n infection in a tooth. see more below. two days after finishing the prescription he developed hives and nausea. he did take benedryl for the hives on an empty stomach and the nausea came on after that. so i guess that could cause stomach upset but still dont know what caused the hives.