Allergy Headache vs. Migraine: How to Tell Them Apart

If you get seasonal head pain with facial pressure and a blocked nose, the odds are strongly in favour of migraine rather than an allergy headache — and the two need completely different treatment. Study after study looking at people who self-diagnose "sinus headache" finds that the large majority meet the diagnostic criteria for migraine instead. That is the single most useful fact in this whole topic, because it means the default assumption most people make about their own head pain is probably wrong.

This is not a technicality. If you treat migraine with decongestants and antihistamines for years, you get poor results and conclude that nothing works. If you recognise it as migraine, an entirely different and far more effective set of options opens up.

Why the confusion is so common

Allergy and migraine share a symptom list that overlaps almost perfectly in the areas people pay attention to.

Both can produce facial pressure. Both can produce a blocked or running nose. Both can produce watery eyes, light sensitivity and a heavy, foggy head. Both are seasonal for a lot of people, and both get worse in spring and autumn.

The reason for the overlap is anatomical. The trigeminal nerve supplies sensation to the face, the sinuses, the nasal lining and the meninges around the brain. Migraine involves activation of that same trigeminal system, and part of what it does when activated is drive autonomic symptoms in the nose and eyes — congestion, tearing, the sense of pressure behind the cheekbones. In other words, migraine can produce sinus symptoms directly, without any sinus disease being present at all.

So a person has head pain plus a stuffy nose, reaches the obvious conclusion, buys a decongestant, and never questions it again.

The distinguishing features

Here is what actually separates them in practice.

Points toward migraine:

• The pain is moderate to severe and often one-sided, or clearly worse on one side
• It throbs or pulses rather than sitting as a constant dull ache
• Nausea, even mild, or loss of appetite
• Light and sound feel genuinely intolerable, not just mildly annoying
• Ordinary movement — walking upstairs, bending forward — makes it worse
• It comes in discrete attacks with clear starts and ends, lasting 4 to 72 hours
• You are essentially fine between attacks
• Any visual disturbance, tingling or speech difficulty beforehand

Points toward allergic or sinus-driven headache:

• Pain is dull, bilateral, pressure-like rather than throbbing
• It tracks tightly with your nasal symptoms — worse when congested, better when clear
• Sneezing, itching in the nose, throat or eyes, which migraine does not cause
• It improves substantially with antihistamines or nasal steroid, and stays improved
• It is present most days during your allergy season rather than in defined attacks
• No nausea, no aura, and light sensitivity is mild or absent

Points toward actual sinusitis, which is a third and much rarer thing:

• Thick discoloured nasal discharge
• Fever
• Reduced or absent sense of smell
• Pain that is markedly worse leaning forward
• Symptoms persisting more than ten days, or improving then clearly worsening again

Itching is the most useful single discriminator on this list. Allergic rhinitis itches — the nose, the palate, the eyes. Migraine does not itch. If itching is a prominent part of your episode, allergy is genuinely in play.

The overlap is real, and it matters

None of this means allergy is irrelevant to migraine. The relationship runs the other way.

People with allergic rhinitis have a meaningfully higher prevalence of migraine than people without it, and among people who already have migraine, those with allergies tend to have more frequent attacks. The mechanism is threshold-based rather than causal: allergic inflammation releases histamine and other inflammatory mediators, those mediators sensitise the trigeminal system, and a sensitised trigeminal system needs a smaller push to tip into an attack.

So the accurate model for most people is not "allergy headache or migraine". It is migraine, with allergy acting as one of the things that lowers the bar.

That reframing explains a very common experience: your usual triggers stop being survivable during pollen season. The stressful week you would normally absorb, the poor night's sleep, the falling barometer ahead of a front — each of them individually manageable in December, each of them enough to trigger an attack in April.

Where weather comes into it

This is where the picture gets more complicated, and more predictable.

Pollen release is weather-dependent. Warm, dry, breezy days ahead of an approaching front produce the highest counts. But those same pre-frontal days are also when barometric pressure is falling — and falling pressure is one of the most consistently reported weather triggers for migraine.

The result is that allergy exposure and pressure change arrive on the same days, systematically, not by coincidence. If you only track one of them, you will misattribute. People conclude they are extremely pollen-sensitive when a good part of what they are feeling is the pressure drop, or the reverse.

The way to untangle it is to look for the days that break the pattern. A high-pollen day under a flat, steady barometer. A sharp pressure fall in midwinter with no pollen anywhere. Your response on those days tells you which driver is doing the work. Checking a barometric pressure forecast alongside a pollen count for a few weeks usually resolves the question faster than any amount of guessing.

Why the distinction changes what you do

Getting this right has direct practical consequences.

If it is migraine, the useful tools are triptans or gepants taken early in an attack, identifying and managing triggers, and — if attacks are frequent — a preventive medication discussed with a doctor. Over-the-counter painkillers taken more than about ten days a month risk medication-overuse headache, which quietly makes everything worse.

If it is allergic rhinitis driving genuine sinus symptoms, the useful tools are a daily intranasal corticosteroid, which is more effective than antihistamines for congestion, plus an oral or intranasal antihistamine, allergen avoidance where practical, and immunotherapy for severe persistent cases.

If it is migraine with allergy lowering the threshold, which is the most common situation of all, you treat both. Controlling the allergic inflammation raises the bar, and the migraine treatment handles the attacks that still get through.

Decongestants deserve a specific warning. Oral and topical decongestants used regularly cause rebound congestion, and in the case of nasal sprays that rebound can develop within days. A lot of people with undiagnosed migraine end up in a cycle of spray, rebound, more spray, worsening headache.

A simple two-week test

If you want to sort this out without waiting for an appointment:

1. Note for each headache: which side, throbbing or steady, any nausea, whether light bothered you, whether movement made it worse.
2. Note separately whether you were itching — nose, eyes, palate.
3. Note the pollen count and the pressure trend for that day.
4. Note what you took and whether it helped within two hours.

Two weeks of that will usually make the pattern obvious, and it gives a doctor something far more useful than "I get sinus headaches."

Frequently asked questions

Can allergies cause a real migraine attack?

Allergic inflammation does not cause migraine, but it lowers the threshold for an attack in someone who already has the underlying tendency. In practice that means more attacks during your allergy season, which feels identical to allergies causing them.

Why do my "sinus headaches" respond to migraine medication?

Because they are migraine. This is one of the clearest diagnostic signals there is — if a triptan resolves it, the mechanism was migraine, whatever the facial pressure suggested.

I get facial pain and a stuffy nose with every headache. Doesn't that prove it's sinus?

No. Trigeminal activation during migraine produces nasal congestion and facial pressure directly. Around half of people with migraine report these symptoms, which is exactly why the misdiagnosis is so widespread.

Does an allergy test settle the question?

It tells you whether you are sensitised to specific allergens, which is genuinely useful information. It does not tell you whether your headaches are migraine — that is a clinical diagnosis based on the pattern of the attacks themselves.

Should I stop taking antihistamines if it turns out to be migraine?

Not necessarily. If you have confirmed allergies, treating them is still worthwhile, and reducing the inflammatory load may reduce attack frequency. What changes is that you stop expecting antihistamines to be your headache treatment.

How do I tell allergy season from pressure season if they overlap?

Look for the mismatched days — high pollen with a stable barometer, and pressure swings out of allergy season. Tracking both for a month separates them reliably. The Pressure Pal city forecasts give you the pressure side, including the direction and rate of change that most weather apps omit.

When should I see a doctor?

If headaches are frequent, escalating, waking you from sleep, accompanied by any neurological symptoms, or if you are reaching for painkillers more than a couple of days a week. Sudden severe headache unlike anything you have had before needs urgent assessment.

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Pressure Pal tracks barometric pressure and its trend for your location so you can separate the weather component of your headaches from everything else that happens to arrive on the same day.