If i stop taking claritin (loratadine) will the side effects go away overnight and by that i mean in a 24 hour period? or will it take a couple of days for all the medicine to be out of my system?

Claritin (loratadine): You do not mention what are your side effects. The antihistaminic effect of the medication may persist for up to 5 days, if you took Claritin (loratadine) d, the decongestant side effects will subside within 24 hours.

About 72 hours: Allergy skin test readings can be affected by taking antihistamine for up to 72 or more hours although the clinical response may not last as long.