Suggest Remedy For Soreness In Skin

My son (24) started experiencing soreness in the skin of his right hand last week. Gradually the tenderness extended up his arm, to his neck, and to the right upper side of his chest. He had some aching in that arm as well, especially in the elbow. I gave him an anti-inflammatory that I had (Mobic). It helped the pain in his elbow joint, so he took another Mobic the next day. Later that evening he started breaking out in an itchy, whelpy, patchy red bumpy rash. It started on the right arm and is now on his neck, eyelids, groin, and behind one knee. He stopped the Mobic. He s been refinishing wood floors, using a sander, but he wears a mask. He s also about 3 months clean from meth addiction.