If it is as other posters have stated as a liver danger, it may be in his best interest to stop, regardless of his intended gains from an substance (I know I'm stating the obvious, but come on, his liver?!)
Maybe a question for other readers, but has anyone experienced this sensation of a sunburn or burning when on any supplement? Or maybe someone who practices medicine can chime in. Good luck to your friend, I certainly hope the damage is minimal if any.
Also, is it actual Urticaria (hives) or is it not visible, only seemingly a phantom sensation or burning or itching?