Where do you find pictures to help diagnose a rash on arms and shoulders?

Although not intended to be used as a substitute for proper diagnosis by a qualified physician, Mayo Clinic offers a slideshow of common skin rashes on its website. The slideshow includes pictures and descriptions of the most common adverse skin reactions.

While several of the 12 illustrated conditions can occur on the arms and shoulders, only a few are normally limited to these areas, according to Mayo Clinic. Pityriasis rosea, more commonly known as Christmas tree rash, normally appears first on the upper back or chest and spreads to the lower back and arms. Side effects and allergic reactions to drugs are also common causes of rashes in these areas.