Your brain itself can’t feel pain. It has no pain receptors. But the tissues surrounding it, particularly the layers of membrane that wrap around your brain (called the meninges) and the blood vessels running through them, are loaded with pain-sensing nerve fibers. When those fibers get activated by inflammation, pressure changes, muscle tension, or chemical signals, the result is what you feel as a headache. The specific cause depends on the type of headache, and most people experience more than one kind over their lifetime.
How Your Head Produces Pain
Pain-sensing nerves in and around your skull are part of a network called the trigeminal system, which covers your face, jaw, and the membranes surrounding your brain. These nerves respond to mechanical pressure, chemical irritation, and inflammation. When something activates them, they send signals to your brainstem and up to higher brain regions, where you consciously register the sensation as pain.
In many headaches, the process involves a signaling molecule released by those nerve endings that widens blood vessels and triggers local inflammation. This creates a feedback loop: the inflamed tissue irritates more nerve fibers, which release more inflammatory signals, which sustains or worsens the pain. That’s why headaches can build gradually and linger for hours even after the original trigger is gone.
Tension-Type Headaches
The most common headache feels like a dull, pressing tightness on both sides of your head, often extending into the neck and scalp. Tension-type headaches aren’t throbbing. They stay at a steady, moderate level and generally don’t stop you from going about your day, though they make everything less pleasant.
These headaches are linked to sustained muscle contraction in the scalp, neck, and shoulders, often from stress, poor posture, or long hours staring at a screen. The tightened muscles compress local nerve fibers and restrict blood flow, which generates that band-like pressure feeling. Emotional stress, lack of sleep, skipped meals, and jaw clenching are the most reliable triggers.
Migraines Are More Than a Bad Headache
Migraines produce moderate to severe one-sided, throbbing pain that worsens with physical activity. Attacks last anywhere from 4 to 72 hours and commonly come with nausea, sensitivity to light, and sensitivity to sound. Some people experience an aura beforehand: visual disturbances like flashing lights or zigzag lines, or tingling and numbness, typically lasting less than an hour before the pain begins.
The underlying process centers on the meninges. Nerve endings there become persistently activated and increasingly sensitive to mechanical stimulation, meaning normal blood vessel pulsing that you’d never notice on a regular day suddenly registers as throbbing pain. Immune cells in the meninges interact with these nerve endings and blood vessels, amplifying the inflammatory response. This is why migraines can feel so much more intense than other headaches: the pain system itself has become hypersensitive.
One striking finding is how often migraines get blamed on sinus problems. A meta-analysis of over 4,300 patients found that 55% of people who believed they had sinus headaches actually met the criteria for migraine. In studies that followed up with confirmed migraine patients, misdiagnosis rates reached as high as 81.5%, with some people going undiagnosed for up to 38 years. If you get recurring headaches you’ve always attributed to your sinuses, especially if they come with nausea or light sensitivity, they may actually be migraines.
Cluster Headaches
Cluster headaches are rarer but far more intense. The pain comes on rapidly, concentrates around or behind one eye, and is often described as excruciating or burning. The affected eye may tear up and turn red, the nostril on that side gets congested or runny, and the face may flush. Individual attacks last 15 minutes to 3 hours, but they repeat daily for weeks or months before disappearing entirely, sometimes for years, before returning in another “cluster” period.
Everyday Triggers That Cause Head Pain
Many headaches trace back to something straightforward happening in your body.
Dehydration is one of the most common culprits. When your body loses more water than it takes in, blood volume drops and your cells shrink, including the cells in your brain tissue. This shrinkage can pull on the pain-sensitive membranes surrounding the brain and expand the fluid-filled spaces inside it. Even mild dehydration, the kind you get from skipping water on a busy day, can be enough to trigger it.
Caffeine withdrawal affects regular coffee or tea drinkers. Your body adapts to daily caffeine by increasing its sensitivity to a naturally occurring molecule called adenosine, which caffeine normally blocks. When you skip your usual dose, that heightened sensitivity kicks in, and blood flow to the brain increases as vessels widen. The result is a dull, persistent headache that typically starts 12 to 24 hours after your last caffeine intake. Interestingly, researchers note that the blood vessel widening may not be the full story. The withdrawal likely also involves broader changes in how pain signals are processed.
Sleep disruption works in both directions. Too little sleep lowers your pain threshold, making you more vulnerable to headaches from any cause. Too much sleep can also trigger headaches, possibly by disrupting your body’s normal chemical rhythms.
Alcohol triggers headaches through multiple paths: it causes dehydration, widens blood vessels, and promotes inflammation. The “hangover headache” is really a combination of all three.
When Painkillers Become the Problem
If you take over-the-counter pain relievers for headaches frequently, you can develop what’s called a medication overuse headache. The International Headache Society defines this as headaches occurring on 15 or more days per month, developing after regular use of headache medication on 10 to 15 or more days per month (depending on the type of medication) for more than 3 months.
The pattern is predictable: you take a painkiller, it helps, the headache returns, you take more. Over time, your pain system recalibrates, and you end up with more frequent headaches than you started with. The only way to break the cycle is to stop overusing the medication, which usually means a rough stretch of worse headaches before things improve.
Red Flags Worth Knowing
The vast majority of headaches are uncomfortable but not dangerous. A small number, however, signal something serious. Clinicians use a checklist of warning signs to identify these, and the patterns worth knowing include:
- Sudden, explosive onset: A headache that reaches maximum intensity within seconds, sometimes called a “thunderclap” headache, can indicate bleeding around the brain.
- Neurological changes: Weakness, vision loss, confusion, difficulty speaking, or decreased consciousness alongside a headache points to possible stroke, infection, or other structural problems.
- Fever with headache: This combination raises concern for infection, particularly meningitis.
- New headache pattern after age 50: A first-time or clearly different headache in someone over 50 has a broader range of serious causes, including inflammation of the arteries in the temples.
- Positional headaches: Pain that dramatically worsens when you stand up or lie down can reflect abnormal pressure inside the skull.
- Progressive worsening over weeks: A headache that never fully resolves and gradually intensifies deserves investigation, especially if it doesn’t fit any pattern you’ve experienced before.
- Headache after head injury: Post-traumatic headaches need evaluation, particularly if they worsen rather than improve over days.
Any of these patterns, especially in combination, warrants prompt medical evaluation. The key distinction is not how severe the pain is, but how different it is from your usual headaches and whether it comes with other symptoms.