“Medication allergy?”

I am sorry but I do not quite understand the question. I am assuming you are asking if cephalexin can be taken by someone who is allergic to penicillin. If that is your question the short answer is a most likely - very low risk of cross-reactivity so it can be tried. However, penicillin allergy is something that is not permanent so I strongly suggests seeing an allergist and having formal testing and challenge done - most people clear that allergy after a few yrs. Establishing if you can safely take penicillins from now on will have great benefits for your future healthcare.