Can the Sun Cause Headaches?

Sunny days are great for being outside, but not if you have a headache. The glare of the sun is a common migraine trigger and can make headaches worse. In fact, sensitivity to bright light, called photophobia, can cause several types of headaches, according to the National Headache Foundation.

"Bright sunlight can trigger a migraine attack because light-sensitive cells in the eye communicate directly with areas of the brain that cause headache pain," says Michael Doerrler, DO, an assistant professor of neurology and a headache specialist at Loyola University Medical Center in Chicago.

As many as 90 percent of migraine sufferers have photophobia. In fact, photophobia is one of the keys to diagnosing a migraine headache, the National Headache Foundation says. Artificial lights that are very bright can also cause photophobia, but glare from the sun is a major trigger. Less commonly, bright sun can also cause headaches in people who get tension headaches, the most common type of headache.

A sun headache can come on when you go from a dark area into bright light, like leaving a movie theater and stepping out into bright sunlight. It's also more likely to develop with harsh, reflected sunlight. Examples include being at the beach, out on the water or out in the snow. You may actually feel pain in your eyes before the headache starts, notes the National Headache Foundation.

The best way to avoid a sunlight headache is to wear sunglasses on any sunny day. Choose dark, tinted glasses with polarized lenses to reduce glare. Wraparound-style sunglasses and a wide-brimmed hat will give you the best protection. Make sure to put on your sunglasses before you go from darkness to sunlight. Darkness widens your pupils and lets more light into your eye when you step into the light, the National Headache Foundation warns. If you feel a headache coming on, get to a dark, quiet place.

The sun can also cause a headache from its heat. Becoming dehydrated from overheating, especially in the summer, is a common cause.

"People are more active on warm, sunny days, [and] being active in the sun can cause dehydration, a very common cause of headaches," says Dr. Doerrler.

Read more: Heat and Headaches

Dehydration is the loss of fluids and blood minerals called electrolytes. When fluid and electrolytes get out of balance, a headache is one of the most common symptoms. On sunny days, you're more likely to be outside exercising, and the heat causes you to lose fluid through sweating.

Symptoms of a dehydration headache include a headache along with thirst, fatigue, dizziness, dark urine and dry mouth, the National Headache Foundation says. To avoid or treat a dehydration headache, drink plenty of water or a beverage designed to replace sugar and electrolytes, like a sports drink. Avoid alcohol, sugary drinks and caffeine as they can increase dehydration.

Other tips? Consider wearing a wide hat and a bandanna around your neck to keep your head cool. Use a cool mist spray to keep your face and body cool. And remember that white clothing reflects the heat of the sun, while dark clothing absorbs it.

For people with migraine headaches, summer can also trigger headaches because of the fragrances in summer products like sunscreen and insect repellent, the American Migraine Foundation notes. Odors are a common migraine trigger.

Read more: 6 Surprising Symptoms of Heatstroke and Heat Exhaustion You Need to Know This Summer

"Any stress or struggle can upset the delicate balance of your body and brain and trigger a headache," says Dr. Doerrler. That includes the stress of photophobia and the struggle of dehydration. The good news is that with a little planning, you can still enjoy the sun and avoid the headache.