Short answer: a headache is a symptom — head pain of any cause. Migraine is a specific neurological disorder with diagnostic criteria defined in the International Classification of Headache Disorders, 3rd edition (ICHD-3). The features that distinguish migraine from a tension-type or other headache are systemic: nausea, sensitivity to light or sound, worsening with activity, and a characteristic 4–72-hour duration.
This page lays out the actual ICHD-3 criteria, the differences between the major headache types, and the surprisingly common case of “sinus headache” that turns out to be migraine.
Headache as symptom, migraine as disorder
The word “headache” describes pain in the head. Almost everyone gets headaches at some point. The cause might be a tension-type headache, a migraine, a cluster headache, dehydration, fever, a hangover, a medication side effect, or something rarer.
“Migraine” describes a specific neurological disorder with a characteristic cluster of symptoms. The mechanism involves cortical changes, the trigeminovascular system, and neurotransmitter shifts (most notably the CGRP pathway). It’s a biological condition that runs in families and shows up on brain imaging research as patterns of cortical excitability — not just “bad headaches”.
This distinction matters because:
- The treatments are different (acute and preventive migraine medications target the underlying pathway, not just the pain).
- The prognosis is different (migraine is chronic and recurrent; tension headache often isn’t).
- The patient experience differs hugely — migraine commonly produces disability that tension headache rarely does.
The ICHD-3 criteria for migraine
A migraine attack (without aura — the more common subtype) meets ICHD-3 criteria if:
A. At least 5 attacks meeting criteria B–D.
B. Lasting 4–72 hours (untreated or unsuccessfully treated).
C. Has at least 2 of these 4 characteristics:
- Unilateral (one-sided) location
- Pulsating quality
- Moderate or severe pain intensity
- Aggravation by — or causing avoidance of — routine physical activity (walking, climbing stairs)
D. During the headache, at least 1 of:
- Nausea and/or vomiting
- Photophobia (light sensitivity) AND phonophobia (sound sensitivity)
E. Not better accounted for by another ICHD-3 diagnosis.
That’s the formal definition. The practical sniff test: if your “headache” makes you want to lie down in a dark, quiet room and the thought of climbing stairs makes it worse, it likely meets migraine criteria.
The major headache types — side-by-side
| Feature | Migraine | Tension-type | Cluster |
|---|---|---|---|
| Pain quality | Pulsing | Pressing, band-like | Stabbing |
| Location | Often one-sided | Both sides | One-sided, around eye |
| Intensity | Moderate–severe | Mild–moderate | Severe |
| Duration | 4–72 h | 30 min–7 days | 15–180 min |
| Activity makes worse? | Yes | No | Worse with lying down |
| Nausea / vomiting | Common | Rare | Rare |
| Light / sound sensitivity | Common | Rare | Rare |
| Autonomic symptoms (tearing, runny nose) | Rare | Rare | Common, same side |
| Prevalence | ~14% lifetime | ~40% lifetime | ~0.1% |
A migraine attack and a bad tension-type headache can feel similar in the moment. The disambiguator is usually the company the pain keeps: the systemic symptoms (nausea, light/sound sensitivity) are migraine’s signature.
”Sinus headache” — usually isn’t
This is one of the most common misdiagnoses in primary care. The 2004 American consensus paper found that roughly 80–90 percent of patients who self-diagnose “sinus headache” actually meet migraine criteria when properly evaluated.
The confusion is reasonable: migraine often produces facial pain, pressure around the eyes, nasal congestion, and tearing — all classically thought of as sinus symptoms. The honest test:
- True sinus headache requires infection (sinusitis) with characteristic mucus, fever, and bacterial or viral signs on examination.
- Migraine masquerading as sinus produces the same facial pain pattern without the infection — and the cluster of classic migraine features (nausea, sensitivity) is usually also present.
If you’ve been treating “sinus headaches” with decongestants for years without much benefit, the differential is worth raising with a clinician.
When a headache needs urgent evaluation
These features mean a “headache” should be evaluated now, not tracked in an app:
- Sudden, severe — a thunderclap headache reaching maximum intensity in under a minute.
- New pattern after age 50.
- Headache with fever, stiff neck, rash, confusion, or focal neurological deficits.
- Worst headache of your life.
- Headache after head trauma.
- Progressive worsening over days/weeks.
These can signal subarachnoid haemorrhage, meningitis, mass lesions, or other emergencies. Migraine forecasting apps are not useful here; emergency department evaluation is.
What Hermly assumes
Hermly assumes you have an established migraine diagnosis (formal or working) and that your attacks generally fit the ICHD-3 pattern. The model is trained on data from individuals with recurrent episodic migraine. It is not appropriate for:
- One-off severe headaches that haven’t been evaluated.
- Cluster headache (different pattern, different mechanism, very different treatment).
- Secondary headaches caused by another condition.
If you’re unsure where your headaches fall, the ICHD-3 criteria are the formal reference, and a neurologist or headache specialist is the right place to start.