How much is too much when it comes to meds?

My 6 yr old English Springer Spaniel is currently being treated for a suspected allergy. Symptoms are recurrent ear infections & a rash on her abdomen. Anyways, the vet put her on Cephalexin (an antibiotic), Chlorpheniramine (antihistamine), Prednisolone (steroid), and Tresadem for ear drops. She is handling this cocktail of drugs really well & takes them like a champ, but also is due for her yearly shots and a Frontline app. Just seems to me like an awful lot of STUFF is being introduced into her system so maybe I should hold off on adding more until she is off these meds. I wrestle with getting all the recommended vaccinations for my dog each year anyway. I have heard different opinions on whether boosters truly necessary. Any advice would be appreciated.