bright lights
severe heat, or other extremes in weather
changes in barometric pressure
hormonal changes, such as estrogen fluctuations during menstruation, pregnancy, or menopause for women
drinking alcohol or caffeinated drinks
foods such as aged cheese, salty, or processed foods
consuming food additives, such as aspartame (an artificial sugar) or monosodium glutamate (MSG)
eating foods that have the additive tyramine, which is found in soy products, fava beans, hard sausages, smoked fish, aged cheeses, and Chianti wine
excess stress
loud sounds
physical activity
skipping meals
loss of sleep
taking certain medicines, such as oral contraceptives or nitroglycerin
unusual smells.