If you can, try to get a referal to a dermatologist for your rash. You may well be right about it being from the sun, and Katharine's advice about sun screen is spot on.
A dermatologist is the best one to advise you about treatment for the rash.
Cortisone cream can be useful but in the long term it causes thinning of the skin, so it is best used sparingly and for as short a time possible.
I see you are on plaquenil. This will help lupus skin rashes, but may take a while to get to full effectiveness.
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