<s>[INST] Just saw a patient (11yo) prescribed cephalexin for 10 days for cellulitis of toe 5/31/14. Sensitivities included cefazolin but not cephalexin. Can these drugs be used interchangeably? Child presents today with scattered maculopapular rash and red skin with hot flashes , malaise since yesterday. Am wondering if this is a drug vs staph infection rash. She looks ill. Did not do vitals or examine as knew needed more evaluation than available in retail clinic. [/INST] Hi..your paediatrician was right in starting Cephalexin for cellulitis as it is a good antibiotic of skin and soft tissue infection like cellulitis and has narrower coverage too. But as you say the kid is still ill - I would look for 2 possibilities - 1. Is the duration of Cephalexin already more than 3 days - without good response?2. Are we dealing with a more virulent organism - if so I would prefer Clindamycin.Regards - Dr. Sumanth </s>