Sensitivity/allergic response to medication

Part of the reason why I could not get my GP to listen to my heat symptoms was that I had simultaneously a fiercely itchy head-to-toe rash and it was clearly felt that if they could find the correct cream to remove the rash everything else would vanish away. After 9 months of creams and pills I began to realise that the rash was worsened by taking oral medications and so I reduced pill-taking to a minimum. This, combined with a double dose of antihistamines, made a huge improvement. Taking new medication (such as antibiotics or pain-killers) brings the rash back with a vengeance. Does that sound familiar to anyone or is this sensitivity to drugs not connected to the EM? It has been a great comfort to find all my other symptoms shared by so many of you lovely people.