If you think you have a sinus headache, think again, according to an Arizona headache specialist. You may have a migraine.

In a new study, almost nine out of 10 people who thought they had sinus headaches actually had migraines, according to Dr. Eric J. Eross, an associate consultant in neurology at the Mayo Clinic in Scottsdale.

Eross and his colleagues studied 100 people who thought they had a sinus headache. After evaluating the patients, however, the researchers concluded that 63 percent had migraines and another 23 percent had probable migraines.

Eross presented the results of the study in Vancouver at the annual meeting of the American Headache Society.

Misclassification of migraines as sinus headaches is a problem of “guilt by provocation, location and association,” Eross said in an interview with Reuters Health.

In many cases, headache symptoms were provoked by changes in weather, seasonal changes and exposure to allergens, Eross explained. Headache sufferers often assume that these triggers cause sinus headaches, but they can all trigger a migraine, Eross explained.

Also, the location of headache pain can often confuse people, according to Eross. When people experience pain over their sinuses, they often assume it is caused by a sinus headache when, in fact, migraine can cause pain in that region, too, Eross noted.

Furthermore, migraines often affect just one side of the head, so people believe that a headache that affects both sides is not a migraine, according to the Arizona researcher. But migraines can affect both sides at once, he said.

Headaches are sometimes mistakenly classified as sinus headaches because they occur along with symptoms that are associated with allergy and sinus trouble, including a runny nose and watery eyes, Eross said.

But in most people in the study, the headache pain itself triggered these symptoms, he found. And in a smaller group of people, symptoms of allergic rhinitis, such as a runny nose, actually triggered a migraine.

The misclassification of headaches can have a long-term impact on quality of life, as people are less likely to receive the most effective treatment, according to Eross.

In the study, over-the-counter pain relievers were the most commonly used medications, followed by non-prescription antihistamines. Only about 10 percent of headache sufferers had been prescribed drugs called triptans, which Eross described as the “gold standard” for treating migraine.

Although triptans were used the least, people who took them were most satisfied with the treatment, according to Eross.

He noted that people in the study had been experiencing what they thought were sinus headaches for an average of 25 years.

Eross encouraged people who think they are having sinus headaches to ask their doctor if they might have a migraine. In many cases, it may be a good idea to see a headache specialist, he said.