[header] How to treat a rash on the neck [title] Evaluate your circumstances before the rash appeared. [step] Where you were and what you were doing before the onset of the rash can provide important clues as to what caused the rash. Think about anything new or unusual that you might have been exposed to. 
[substeps] If you wore a new necklace for the first time, tried a new lotion or soap, or ate a new food, your rash may be an allergic reaction. Make note of how much time passed from the initial exposure until the development of the rash.