Vasodilation of the blood vessels may be caused by consumption of, or exposure to, nitrates and nitrites, which may trigger a vascular headache.
Nitrates are found in some medications for heart problems and in some chemicals used in the food and beverage industry.
The nitrites are used to preserve the red coloring in processed meats (hot dogs, salami, bacon, etc.) and as preservatives in many other food products. Sensitivity to these agents varies greatly. The amounts used in most foods are usually very minimal but may trigger a headache in some sensitive individuals. Keeping a headache diary may help identify these triggers.