My grandson, who doesn t live nearby, has a severe rash, some blistering and joint swelling in the ankles wrists and knees. No itching. they are at an emergency clinic and awaiting lab results. If it keeps getting worse they will go to the hospital emergency. He hasn t been near poison ivy, has only had tylenol in the last 12 hours. I m just a grandmother trying to help them from across the country without making matters worse. Any suggestions on what the cause is?