Redness in the face and arms.?

Ok i dont have alot of details but my best friend today all of a sudden got very red in his arms and his face. Could this be relaited to drug use? if so what drugs. Im very concerned. He hasent been acting himself lately. Anythoughts?Redness in the face and arms.?
I have an Asian friend that gets flushed when he drinks alochol. That could be it.
that may be allergy ..did he change the type of drug recently...or it may be somthng else...if it persist more than 2 days pleese seek a doctor