Suggest Treatment For Itchy Red Rash On Neck And Chest

I have an itchy red rash on my neck and chest. I have occasionally noticed irritation in the past few days but not noticed the redness. Nothing is new in my diet or clothing or detergent. The only new product is a Rejeuvaderm lotion I was putting on my neck; not usually on my chest, for the last two weeks. I have not used it for 2 days now, but the rash is quite active today. Your suggestions/comments appreciated. Carol Van Dorn