What Causes Right Sided Headache, Rashes On The Chest, Arms And Legs?

My Husband has had a Headache on/off for about 2 months. Not a typical headache. It is on the right side of his scalp, radiates to his sinuses and jaw. It comes and goes. worse in the eve. If he takes ibuprofen the headache pain does get much better, but after 4-5 hours returns. He also broke out in a rash about 2 weeks ago. The rash is on the chest, back arms and legs. The rash does not itch and it gets worse and better, but never fully goes away. He has fatigue, but that is better. His lymes test was neg, CBC wnl. He did have a crp of 15. Mono neg, strep neg. fifth disease neg. He is having an MRI of the head tomorrow. He did sinus x rays neg, chest x ray neg. He has a small bump on the back of his neck that came with these symptoms as well.