NEW YORK - Many people with nasal allergies suffer from migraine headaches as well, new research indicates. This suggests that the compound that causes allergy misery - histamine - may also be involved in triggering migraines.

In a study of nearly 300 children and adults, researchers found that 34 percent of those with allergic rhinitis - better known as hay fever - also had symptoms that met the diagnostic criteria for migraine. That compared with only 4 percent of study participants without hay fever.

The findings might prompt doctors to have a "heightened awareness" of migraine symptoms among patients with nasal allergies, the researchers say in the Annals of Allergy, Asthma & Immunology.

Past research has suggested that many headaches assumed to be sinus headaches may instead be migraines. Sinus headaches occur when the sinus cavities become inflamed, with allergies being one cause. However, sinus headaches can be hard to distinguish from migraines because they share a number of features.

Migraines are marked by throbbing pain, typically concentrated on one side of the head and often accompanied by nausea and sensitivity to light and sound. But they can also come with facial pressure, nasal congestion and other signs often ascribed to sinus headache.

For the new study, researchers led by Dr. Min Ku of Allergy & Asthma Care PA in Haddonfield, New Jersey, surveyed 294 adults and children with and without nasal allergies.

They found that patients with allergies were 14 times more likely to have symptoms consistent with migraine.

The connection makes sense, according to Ku's team, because histamine - a chemical released by immune system cells during allergic reactions - may trigger migraines by causing inflammation and blood vessel dilation.

Distinguishing migraines from sinus headaches is important to getting proper treatment. Migraines can be managed with common painkillers, but other medications - such as a class of drugs called triptans - may be necessary. In addition, people with frequent migraines may need preventive drugs.

There is no evidence, Ku's team notes, that the antihistamine medications used for hay fever can relieve migraines. But that's not surprising, they add, because antihistamines have little effect on the blood vessel dilation triggered by histamine.

The researchers are currently studying whether topical steroid medications can treat or prevent migraine in people with nasal allergies.

SOURCE: Annals of Allergy, Asthma & Immunology, August 2006.