Zertec. A Med Over The Counter Which I Have Been

Zertec. a med over the counter which I have been taking all along. I have a rash all over my body along with a terrible itch, I have been using Zertec for almost a year now. It works at times, especially at bedtime but now for long. Any suggestions, I have gone to a dermatologist and she told me I have DERMOTOGRAPHISM. It just showed up, the itch is driving me crazy. Any suggestions?