What is allodynia in migraine?

Allodynia is pain or discomfort triggered by stimuli that aren't normally painful — light touch, hair combing, eyeglass frames, jewellery against the skin. It typically develops 2–4 hours into a migraine attack and indicates central sensitisation.

Why does allodynia matter clinically?

Allodynia onset signals that central sensitisation has occurred — the trigeminal system has become hyper-responsive. Acute medication response rates drop significantly once allodynia is present, which is why early treatment is emphasised.

Is allodynia common in migraine?

Yes — about 65 percent of migraine attacks develop some allodynia, and roughly 40 percent of migraine patients have it consistently. It's more common in chronic migraine than episodic.

How do I treat a migraine after allodynia starts?

Triptans still work in some patients, but the response is reduced. Some evidence suggests gepants may retain efficacy better in the allodynic phase. The honest answer is that prevention — taking acute medication earlier next time — has more impact than chasing the established attack.

Allodynia — when light touch hurts during a migraine

Creator: Hermly
Published: 2026-05-16T00:00:00.000Z

Allodynia is pain from stimuli that shouldn’t be painful — combing your hair, putting on glasses, the touch of jewellery against skin, the brush of a pillow. In migraine, allodynia develops 2–4 hours into about 65 percent of attacks and signals that central sensitisation has occurred.

Clinically, allodynia onset is an important marker: once it’s present, acute medication response rates drop. This is the biological reason headache specialists emphasise treating attacks early.

What it looks like

Migraine allodynia is cutaneous — affecting the skin. Typical presentations:

Scalp tenderness — hair combing, hat-wearing, even resting the head on a pillow becomes painful.
Facial sensitivity — eyeglass frames hurt, water on the face during washing feels uncomfortable.
Neck and shoulder area — clothing collars, jewellery against skin.
Extracephalic spread — in severe attacks, allodynia can extend beyond the head and neck to the arms or body.

The mechanism is central sensitisation: trigeminal sensory neurons in the brainstem become hyper-responsive after sustained input from the migraine pain pathway. Once sensitised, they fire from input that wouldn’t normally reach the pain threshold.

Why allodynia matters for treatment

The Burstein 2000 paper in Brain was the foundational finding: patients who took acute medication before allodynia developed had significantly higher pain-free rates than those who took it after. The treatment window is real — and allodynia onset marks roughly the end of the high-response window.

Practical implication: if you have a pattern of consistent allodynia onset (say, 2 hours into typical attacks), the time to treat is during the first 30 minutes of recognisable headache. Waiting “to see if it gets bad enough” usually moves you past the optimal window.

Allodynia in chronic migraine

Allodynia is more common in chronic migraine than episodic — the chronic state involves more sustained central sensitisation. Patients who develop new persistent allodynia may be transitioning toward chronic, and that pattern warrants a preventive-treatment conversation with the prescriber.

What this isn’t

Not a recommendation to take medication on a fixed clock schedule — that’s the path to MOH. The practical guidance is: treat each attack at first recognition, not “as soon as I notice signs every day”.

Not medical advice. Hermly is a wellness app, not FDA-cleared for diagnosis or treatment. This page is informational and should not replace conversation with your doctor. If you're experiencing a sudden, severe, or unusual headache, contact a medical professional or emergency services.