Headaches happen—here’s why 

Published April 8, 2026

Nearly everyone has had a headache, and for some, they are all too frequent. Headache disorders are one of the most common reasons people miss work or school, cancel plans, and seek medical care.

But not all headaches are the same. Some happen on their own. Others happen because of something else. Some occur once in a while. Others become frequent enough that people plan their days around them.¹

What is a headache, really?

A headache is pain or discomfort in any part of the head, including the face, scalp, or neck. While it may feel like the pain is coming from the brain, brain tissue has no pain receptors of its own. Instead, headache pain is caused by the activation of pain-sensitive structures in or around the head, such as the blood vessels, nerves, and muscles of the head, face, and neck. When these structures get irritated, inflamed, or stretched, they send pain signals to the brain. Because these structures are located within or around the skull, the brain processes and registers those signals as pain inside the head, and what you feel is a headache.¹,² 

What are the types of headaches?

Most headaches fall into 2 main groups based on what causes them.² ,³

Primary headaches are the condition itself, not a symptom of something else, and include tension headache, migraine, and cluster headache. They’re caused by overactivity or dysfunction involving pain-sensitive structures in the head, rather than by another health condition. Most of the headaches people experience throughout their lives are primary headaches.

Secondary headaches are a symptom of another health condition, such as a sinus infection, dehydration, high blood pressure, or illness. The headache is the body’s way of signaling that something else is going on.

It’s also common for people to experience more than 1 type of headache over time.

What are chronic headaches?

Another way headaches are described is by how often they happen.

Some headaches are episodic, meaning they happen from time to time. Others are chronic, meaning they happen frequently over time. A chronic headache is defined as a headache that occurs 15 or more days a month for at least 3 months.³ 

This distinction matters. Frequent headaches can start shaping daily life in ways occasional headaches usually don’t. People living with frequent headaches may start planning around them, worrying about the next one, or changing routines to avoid setting one off. Chronic headaches can also affect quality of life, work, school, and relationships. 

The causes of chronic headaches vary and may be influenced by factors like dehydration, vitamin levels, hormone changes, sleep issues, stress, blood pressure, or other underlying health conditions. Many of these can often be addressed. Better understanding of what’s driving the pattern is the first step toward breaking it.²⁻⁵

What are the most common types of headaches?

Tension headaches are the most common type of headache. They can feel like constant pressure or squeezing in the head, face, or neck, or like a tight band of pressure around the head. Tension headaches can last from 30 minutes to 7 days. Common triggers include stress, fatigue, hunger, dehydration, jaw clenching or teeth grinding, and posture that strains the head or neck.¹,⁶

Migraine is the second-most common type of headache. It causes moderate-to-severe throbbing or pulsating pain, usually on one side of the head. Some people also have aura, which can include vision changes such as zigzags, flashing lights, or blind spots before the headache phase begins. Migraine tends to run in families and affects women most often. Common triggers include stress, hormone changes, fatigue, hunger, certain foods and drinks, bright lights, loud noise, strong smells, and changes in weather or altitude.

Cluster headaches are less common but are among the most severe headache disorders. They cause sudden, excruciating pain on one side of the head, usually around or behind one eye. Symptoms on the same side can include a watery or red eye, a runny or stuffy nose, and a drooping eyelid. Attacks can last from 15 minutes to 3 hours and may happen up to several times a day. They often come in clusters over weeks or months, sometimes at the same time of day or night, followed by symptom-free periods that can last for months or even years. While the exact cause is unknown, attacks during a cluster period may be triggered by alcohol or tobacco use, strong odors, bright sunlight, and changes in weather or altitude.

Sinus headaches are a type of secondary headache and a symptom of a sinus infection. They can cause deep, pressure-like pain in the face, forehead, or around the eyes that often gets worse with sudden movement or when bending forward. They usually come with other sinus infection symptoms, like a stuffy or runny nose and sometimes fever. Migraine and sinus headaches share common symptoms, which may make them easy to confuse. Studies suggest that nearly 90% of people who thought they had sinus headaches were actually experiencing migraine.⁶,⁷

What’s the difference between a headache and a migraine?

Migraine is a type of headache, but not all headaches are migraine. Migraine is a neurological condition. It includes head pain, but it’s defined by much more than pain alone.¹,³

What sets a migraine apart is the full picture. The pain is more intense and can last anywhere from 4 hours to 3 days. It’s commonly paired with symptoms like nausea, vomiting, and extreme sensitivity to light, sound, or smell. 

Migraine also follows a pattern. For some people, it unfolds in stages. This can include early warning signs, changes in vision or sensation (called aura), the headache itself, and the final phase, often described as a migraine hangover.¹,⁵

How do triggers set off a headache?

Your body is constantly working to keep its internal systems in balance. Temperature, hydration, blood sugar, blood pressure, hormone levels, and sleep are all monitored and regulated in the background. This steady balance is called homeostasis and is essential for the body to function properly.¹⁻⁷

When that balance shifts, the body has to adjust. For many people, those adjustments happen and they never notice. But for people who are prone to headaches, especially migraine or chronic headaches, the brain can be more sensitive to these changes. 

Different triggers affect the body in different ways. Skipping meals can lower blood sugar. Not drinking enough fluids can lead to dehydration. Certain foods or drinks may affect blood vessels. Weather changes can shift air pressure that may affect the sinuses and surrounding tissues. 

These are real, physical changes the body has to respond to. And for some people, they can be enough to activate pain pathways and trigger a headache. 

Sometimes, all it takes is a trigger like 

• Stress (physical or emotional) 
• Changes in sleep 
• Skipping meals 
• Dehydration 
• Nutrient deficiencies 
• Hormone changes 
• Illness or infection 
• Weather or altitude changes 
• Bright lights, loud noise, or strong smells 
• Allergens 
• Alcohol 
• Tobacco 
• Caffeine 
• Certain foods (such as aged cheeses, processed meats, or chocolate) 
• Artificial sweeteners