A rash from an allergic reaction to medicine has a variable clinical course. Even after the offending drug is discontinued, it can take weeks or months for the drug reactions to disappear. The durarion for the rash to cease is related to the exposure time and the amount of drug the person was exposed to.
It should start to lessen almost immediately, and completely disappear within a week or so after discontinuation of the medicine. If it doesn't then the rash was probably caused by something else and will need treatment.
Depends on numerous factors such as: how bad the rash was, how long medicine was took, and how long the medicine will stay in the body's system. Some medicines can take days to fully empty out of your system.
Well a rash from an allergic reaction to medicine will last about a week at the most depending on whether you continue to take the medicine or not. If you are still taking the medicine, it may last longer.
A rash from an allergic reaction to medicine should not last for more then 2 days. If it does you will need to seek medical attention, because it could be more serious then some cases though, a reaction can be bad enough to stay for a couple of weeks.
I'm currently experiencing a drug reaction from prednisone, imagine that....this is what they use to help treat rashes from allergic reactions! My rash has been here for 5 days today, and slowly, slowly letting up. :-/