Reactions to allergens can trigger migraines. When a person suffers a migraine their superficial temporal artery becomes initially constricted before dilating. The increase of blood pressure in the artery, increases the pain of the migraine. This is why pressing a hand on the side of the head, compressing the artery, relieves the pain. Research has shown that when allergens are avoided the monthly headache rate decreases. It was found that 85% of migraine sufferers studied became free of migraine simply by avoiding dairy products and wheat. It is also recommended that people prone to migraines avoid eating a number of different foods at any one meal. This is because the combination of chemicals in different foods can create a reaction in the human body. Avoiding artificial food additives such as preservatives, colorings and flavors can also reduce the incidence of migraine.