 [ Symptoms ] why has my 5 month old gone from sleeping through the night to waking up crying we have to feed her to help her sleep [ Disease ] there are plenty of other effective antibiotics like erythromycin or the cephalosporins some penicillin allergic people may have a cross over allergy to this class however he needs to be under the care of a good dentist now let the dentist determine the type of treatment and antibiotics if he has an abscess he needs more than just a prescription for a non penicillin based antibiotic dental infections like you are describing need immediate and definitive care