Hot, red skin, burning sensation on hands, feet, thighs, neck/chest, what could be causing this?

Reaction: sounds like an allergic reaction. Try Benadryl (diphenhydramine) 50mg

Sounds worrisome: though autoimmune disorders as well as any skin rash could cause such symptoms. Of course I'm guessing you have ruled out sun burn as a cause? I would see a healthcare provider as soon as possible if you continue to have these symptoms. Thanks for trusting in HealthTap.