Exercise, heat,
skin friction, hot baths, hot drinks, cold exposure (especially swimming), sunlight, emotional stress, spicy foods.
Medicines, oral and injected: Aspirin, alcohol (in cough compounds and pediatric elixers), morphine, codeine, dextromethorphan (“DM” in cough compounds), nonsteroidal anti-inflammatory agents, procaine, opiates (codeine, Demerol, morphine), thiamine, high molecular weight polymers (dextran).
Medicines, topical: Topical antibiotics containing polymyxin B.