It is hard to say with any certainty as to what is causing your rash but I have a couple of ideas. For one , from your list of meds I would say that the Allopurinol is the most likely to cause a rash from the list of meds that you take. You might try to discontinue the med for a couple of weeks to see if this leads to improvement of the rash.
If you wear a chain then a contact dermatitis is possible. If you do, then discontinue wearing the chain for a while.
If dry , scaling and itching it could in part be related to the dryness indoors during the winter months and you might benefit from using a moisturizing lotion several times a day.
You might try a few of these ideas to see if they fit but remember that I can't see your rash and I don't know the details of its characteristics. You may need to see your doctor or a dermatologist to get a definite diagnosis and treatment.
I hope this info helps. Follow up questions are welcome if you have any.
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Anthony Bray MD