Researchers from the University of Copenhagen, Denmark studied the relation between natural trigger factors and migraine with aura (MA) in 27 patients who reported that bright or flickering light or strenuous exercise would trigger their attacks. Patients were provoked by photic stimulation, strenuous exercise, or a combination of these two factors. Three patients (11%) reported attacks of MA following provocation. An additional 3 patients reported migraine without aura (MO) attacks. Following exercise, 17% developed an aura, 4 out of 12 patients reported migraine (1 MA, 3 MO) headaches, while no patients developed attacks following photic stimulation alone. Patients were exhausted after the exercise and 5 developed nausea, 2 vomited, and 6 complained of dizziness. Light stimulation, especially low frequency of 1-5 Hz, was considered unpleasant but was well tolerated. 
COMMENT. In an editorial , the trigger effect of exercise demonstrated in the present study is considered small (10%) compared to that of nitroglycerin infusion that induces migraine and premonitory symptoms in 75% of patients . Food triggers or sensitivities, frequently discussed in the migraine literature [4, 5], have variable effects or mechanisms. As an example, ingredients in chocolate implicated in the mechanism of dietary-triggered migraine include phenylethylamine, theobromine, caffeine, and catechin. These chemicals may initiate a headache by alteration of cerebral blood flow and release of norepinephrine from sympathetic nerve cells . Alternatively, a chocolate trigger may be explained by a premonitory food craving; and chocolate is consumed because of a response to a migraine attack and not a cause. Also, an urge to exercise may represent a premonitory symptom of migraine. The classic advice to avoid suspect triggers may be incorrect, and the migraineur should instead, be advised to become habituated to the provocative factor . Indeed, some adult patients advised to avoid chocolate and red wine would rather suffer an occasional migraine.