Just because everyone gets headaches doesn't mean we all get the same headaches. There are a bunch of different kinds — and women are more likely to get most of 'em. Plus, not only are headaches painful and far too common, but they're also annoyingly mysterious. They may come on for seemingly no reason at the most random of times. And experts still aren't sure exactly what causes them.What they do know is that essentially, a headache happens when the blood vessels and nerves that surround your brain (over)react to your body's chemical signals. Those, in turn, may be cued by things in your environment, such as certain types of light, sounds, or foods. But exactly why or how that happens is still unknown.And of course, not all headaches cause the same type of pain. Headaches can be a symptom of all sorts of issues, from sinus infections or allergies to simply forgetting to eat lunch. We know that tension headaches, for instance, tend to affect both sides of your head and are commonly caused by stress. We also know that cluster headaches are excruciatingly painful and may occur daily (or several times per day) for a period of weeks or months before going away for just as long. And we know that migraines , which are characterized by painful throbbing on one or both sides of the head, may also start with visual symptoms, such as a shining "aura" about 30 minutes before the actual headache hits.Minor headaches that only come once in a while can usually be tamed with over-the-counter meds, such as ibuprofen, and are nothing to worry about. But if you find you're getting frequent headaches (at least two per week ), there's no need to suffer on your own. In some rare circumstances, a headache that's new and severe can be a sign of serious issues, such as a brain tumor . So if your headaches are coming in different patterns or they're the worst headaches you've ever had, it's a good idea to get them checked out.But even if they're not a symptom of something scarier, your doctor may recommend that you see a headache specialist. The specific cocktail of things that trigger headaches is different for everyone, so a specialist can help you narrow down what's going on and pinpoint the factors in your life that may be subtly contributing to your personal brand of headaches.Still, knowing common headache triggers can provide some helpful clues to get you started. Ahead, we cover 26 of the most commonly reported headache and migraine causes so you can be on the lookout.