A migraine trigger is anything that consistently results in a headache. Common triggers include, alcohol, lack of sleep, and skipped meals. Many people have food triggers and smell triggers. But everyone is different. One migraineur can eat chocolate until they are three hundred pounds and not get a headache while the next person with the same headache type can't walk by a candy counter without getting a headache. Rather the listing all the things that ever gave anybody a headache, it is better to be observant about the events that surround your headaches and when you see a pattern, act accordingly.