Have Sensitivity To Pcn And Sulfa. PA Prescribed Clindamycin. Concerned

Have sensitivity to Pcn and sulfa. PA prescribed clindamycin. Concerned since I've had terrible itch (similar to yeast infection from when I was young) in perineal area since before Christmas- not vaginal opening, but more on labia and anus. Thought it was more of a cyst, itch is releived by Allegra topical. Also culture was negative. Had my "routine" blood work this morning, Should I wait for the lab results before taking this?