I mentioned something almost exactly like this in an earlier thread. Me and my buds call it "whitefacing" basically you smoke too much adding the high to alot of smoke inhaled depriving the brain of oxygen add on higher blood pressure because you keep thinking it'll get worse. If he just calms down it should pass in a few minutes. I find cold water and not too much moving around (but sit upright! dont lie down) should fix ya up. I've heard of allergies to cannabis but its generally actually an allergy to any form of smoke. But there is documented cases, if he's allergic it is his own damn fault as Bman pointed out though lol. , Most people who are allergic either have much more severe symptoms and/or actual physical symptoms (hives itchiness from the smoke touching their skin etc).