My Son Is Sick He Has Croup Cough And He

My son is sick he has croup cough and he is on breathing treatments he has taken these many times before I gave him medicine doc prescribed for him we noticed about an hour later he had spider web /beehive purplish/bluish veins all over his chest back and arms. Is this something maybe an allergic reaction or maybe just from running around Lil bit since he is having Lil trouble breathing ? Any advice ?