Failed 3 rounds of antibiotics child still has pus in ear allergic to omincef and amoxicillin what else can we try?

Culture: Although this is rarely necessary, culture may be helpful in determining which antibiotic to use if there have already been 3 failures. Also, penicillin allergy needs to be confirmed (some allergies resolve with time and some are not even true allergy to begin with). An Allergist can perform testing. If penicillin still the best choice, a desensitization procedure is worth considering.

Hard to say: Since you didn't list the previous meds it is hard to suggest one that may work. Success in clearing an otitis after 3 meds often drops to below 25% regardless of what is tried. If a sample of the puss is obtained it may help. However, at some point the middle ear fluid may be so thick drugs cannot penetrate & kill the germs. At that point removing the pus during tube placement may be the best rx.