My Son Has Had A Head To Toe Rash On

My son has had a head to toe rash on and off for 3 days now. The rash comes and goes over his entire body. Red, raised bumps in uneven patterns. When the rash on his body goes away his hands and feet are tingly, painful and very itchy....when the rash comes back over his body then the pain, itchiness in his hands/feet go away. He has no fever, no cough, and no headache. He hasn't changed his diet, or medication, or soap, or laundry detergent.