I was prescribed cephalexin for staph but it gave me an allergic reactions. i told my doctor i have been taking it for 4 days but its was 3 day. he prescribed me doxycycline will it still be affective he prescribed me doxycycline 100mg for 5 days?

Doxycycline is not the drug of choice for staph infection but it is an acceptable because you are allergic to cephalexin, probably penicillin and its derivative. The duration of treatment depends on where the infection is. In general, a five day course is probably enough for a simple infection.

I agree with Dr Le that Doxycycline is acceptable as an option, However, it also depends on where the staph infection might be as different substitutes for cephalexin exist depending on location. Also for some bad kinds of staph called MRSA, a sulfa drug like Septra/bactrim would be a better option

I agree with Dr. Le's comments, but would stress that a more effective dose of doxy for an established staph infection would be 100 mgs twice a day for 5 days