... and Vancomycin ( ignore the spelling) for 4 days in the Hospital with no reactions then I was given 300 mg clindamycin caps to take at home for 14 days along with Bactrim 800-160 mg I developed a rash and hives on my arms and hands, like an allergic reaction to something, I am allergic to penicillin I did not develop this reaction in the hospital while taking IV clindamycin, my question is can a person develop an allergy to clindamycin like over night and how long will these hives last taking Benadryl that my doctor has me taking