What Causes Rashes And Red Spots On Legs And Arms While On Spironolactone?

I was prescribed Spironolactone 100 mg, twice daily and after 2-3 weeks on the medication I have developed a skin rash mostly on my legs and arms as well as red spots on my arms. It seems to be worse at night. I notified the prescribing physician and she recommended ceasing the medication and to take Benadryl. It has been 4 full days since I stopped the Spironolactone and I am not seeing relief of symptoms. Is it advisable to go to the ER or wait until Monday to be seen by PCP?