If you suffer from headaches, you’re probably all too familiar with the throbbing head pain or scalp tightness that signals another one is on its way.

But there’s different red flag you should know about. Researchers in Germany have uncovered a symptom that can sometimes be worse than the telltale head pain that most people associate with headaches. When this symptom is overlooked, a proper diagnosis and treatment can be delayed, causing people with headaches to suffer unnecessarily.

Recent finding: Researchers asked nearly 3,000 people with headaches, including migraines and extremely painful headaches that often occur around the eye (known as cluster headaches), to complete questionnaires about their headaches.

When the numbers were crunched, 10% of the study participants reported experiencing facial pain with their headaches. (Note that anyone with dental problems that could have led to facial pain was excluded from the study.)

Interestingly, facial pain was more common with some types of headaches than others. For example, facial pain occurred in 45% of those with paroxysmal hemicranias (a rare headache that causes short and severe attacks on one side of the head)…21% of those with hemicrania continua (a rare headache that triggers continuous headache pain that varies in severity)…and 20% of sufferers of short-lasting unilateral neuralgiform headache, which leads to very frequent attacks on one side of the head.

Of the 2% of migraine sufferers who had facial pain, nearly half reported that their pain was felt predominantly in the face, not in the head.

A new pain syndrome: The study also identified six people who reported constant unilateral facial pain (one side only) in addition to 10-to-30-minute attacks of facial pain several times a day. This is the first time these particular symptoms have ever been reported, according to study author Arne May, MD, PhD, professor of neurology at the University of Hamburg in Germany. Based on these symptoms, Dr. May suggested that this pain syndrome be named “constant unilateral facial pain with added attacks.”

“For a better understanding of these types of facial pain and ultimately for the development of treatments,” explained Dr. May, “it’s crucial that we understand more about facial pain and whether it is the same disease as the headache, but showing up in a different place, or whether they are two different syndromes.”

Caveat: Because the study participants answered questions about past headache experiences, their recollections about symptoms may not be entirely accurate. That said, it’s also possible that the actual number of facial pain sufferers is even higher than reported.

Takeaway: If you experience any type of facial pain with or without head pain, be sure to tell your doctor so that you can discuss treatment options.