Allodynia in Migraine: Why Touch Suddenly Hurts
Allodynia is pain from something that should not hurt at all. During a migraine attack, it can mean your scalp hurts when you brush your hair. It can mean your skin hurts under a necklace or a shirt collar. Your nervous system turns up its own volume. Ordinary touch gets read as pain.
This can feel strange the first time. Even a little scary. But allodynia is a known part of migraine. Understanding it can help you treat attacks better.
Key takeaways
- Allodynia is pain from a touch, movement, or temperature change. Normally, none of these would hurt.¹
- About 60% of people with migraine feel it at some point. Estimates range from 40% to 70%, depending on the study.²
- Allodynia comes from central sensitization. This is when nerve cells in the brain and spinal cord get overly excitable.²
- It usually builds gradually as an attack goes on, rather than appearing all at once.²
- Treating an attack early, while pain is still mild, gives your medicine its best chance to work.²
- Allodynia is linked to a higher chance that migraine becomes more frequent over time. Mention it to your headache specialist.³
What is allodynia?
Allodynia is pain from something that would not normally hurt.¹ A light touch. A bit of pressure. A small change in temperature. Any of these can suddenly feel like pain.
People with migraine often describe this as their hair hurting. Brushing it can set it off. So can resting your head on a pillow. Or a light tap on the wrist.¹ Some people say it feels like a sunburn across their whole body, even though nothing touched their skin.
Allodynia is not just "more pain." It causes no tissue damage.¹ It is also not one of the four phases of a migraine attack, the way prodrome or aura are. It is something that can show up once an attack has already started.
What does allodynia feel like during a migraine attack?
Allodynia shows up in different forms. It depends on what triggers it.
Allodynia usually starts on the same side as the headache. Often around the scalp, face, or forehead. This is called cephalic allodynia. In some people, especially with chronic migraine, it spreads to the arms, legs, or trunk. This is called extracephalic allodynia. It is a sign that more of the nervous system has become sensitized.²
In chronic migraine, allodynia does not always wait for an attack. Some people notice it between attacks too. This is more likely the longer someone has lived with chronic migraine. It points to ongoing sensitization, not just a symptom tied to one attack.⁴
Why does migraine cause allodynia?
Allodynia comes from central sensitization. This means nerve cells in your brain and spinal cord get more excitable than usual. They start firing from signals that would not normally cause pain at all.²
During a migraine attack, trigeminal neurons become more active. These are the nerve cells that carry pain signals from your head. If the attack goes on long enough, that activity spreads. It reaches nerve cells further up the pain pathway, in the spinal cord and thalamus. Once these cells are sensitized, they can fire from ordinary touch, not just from the headache itself.² That is what allodynia feels like from the inside.
Researchers are still working out the details. Recent work points to CGRP, a protein already known for triggering migraine pain. It may also help keep this sensitization going as migraine becomes more frequent.⁵ That is one reason CGRP-targeting treatments are now a focus of allodynia research, not just migraine research.
This process usually builds as the attack goes on, rather than appearing all at once.²
How common is allodynia in migraine?
Allodynia is common. The exact number depends on who is studied and how allodynia is measured. Across large studies, researchers estimate that 40% to 70% of people with migraine feel it. Most studies land close to 60%.²
Allodynia is also more common with certain migraine patterns. People with frequent attacks, migraine with aura, or chronic migraine are more likely to have it. They are also more likely to have it severely.² A 2024 study looked at more than 61,000 US adults with migraine, as part of the OVERCOME research project. Severe allodynia was about three times more common in people who sought medical care for their migraine than in those who did not.⁶ People whose allodynia affects their life more are more likely to bring it up with a doctor. That is exactly what headache specialists want people to do.
Does allodynia affect treatment?
Yes. This is one of the most useful things to know about allodynia. But the science here has gotten more precise in recent years.
Older research suggested that once central sensitization sets in, triptans lose much of their effect. Newer trial data tell a more careful story. One large trial tested the triptan almotriptan. Allodynia itself did not lower how often people became pain-free, as long as they treated the attack while pain was still mild. What mattered most was how bad the pain already was when treatment started. Allodynia by itself mattered less.² The practical advice stays the same: treat early, before pain builds.
There is also good news for preventive treatment. A 2021 trial tested erenumab, a CGRP-targeting preventive medicine. It worked just as well for people with moderate to severe allodynia as for people without it.⁷ Having allodynia does not mean your preventive options are limited.
If you already have allodynia by the time you treat an attack, talk with your clinician about your options. Some people find other approaches help. OnabotulinumtoxinA, a preventive treatment for chronic migraine, can ease allodynia symptoms for some people alongside headache days.⁴
What can help?
A few strategies are worth building into your migraine plan if allodynia is part of your pattern.
Treat early. Take your acute medicine as soon as you recognize an attack starting, ideally while pain is still mild.² This gives medicine the best chance to work before sensitization takes hold.
Track your pattern. Keep a headache diary. Note when allodynia shows up during an attack and how bad it gets. This helps your headache specialist see how sensitized your nervous system has become. They can use that to adjust your plan.
Ask about prevention. Allodynia is one of the better-established risk factors for migraine becoming more frequent over time.³ Raise it with your clinician, even if it does not feel like the main problem. An effective preventive treatment can lower how often you reach the point of sensitization at all.
Do not blame yourself for it. Allodynia is not a sign that your migraine is unusual or that you are managing it wrong. It is a well-documented part of how migraine behaves in a large share of people.
Living with headache or migraine? The specialists at Haven Headache & Migraine Center are here to help. Book a virtual consultation.
Frequently asked questions
Why does my scalp hurt during a migraine attack?
This is usually cephalic allodynia, pain from light touch that develops once central sensitization sets in during an attack.¹ Brushing your hair or resting your head on a pillow can trigger it.
Is allodynia dangerous?
No. Allodynia can feel distressing, but it is not dangerous. It does not mean tissue damage.¹ It eases as the migraine attack ends.
Does everyone with migraine get allodynia?
No. Roughly 40% to 70% of people with migraine feel it at some point, depending on the study.² It does not happen with every attack. It is more common with frequent attacks, aura, and chronic migraine.
Why does my medicine stop working once my skin feels sensitive?
It is not quite that simple. Newer research suggests pain level matters more than allodynia itself.² Treat the attack early, while pain is still mild. That gives medicine its best chance to work.
Can allodynia happen between migraine attacks?
In chronic migraine, some people have ongoing allodynia even between attacks. This is more likely the longer someone has lived with the condition.⁴ This pattern is worth discussing with a headache specialist.
Should I be worried if I have allodynia?
Allodynia itself is not an emergency. But it is worth mentioning to your headache specialist. It is linked to a higher chance that migraine becomes more frequent over time.³ It can also help guide treatment decisions.
Medically reviewed by: Alicia Chang, MSN, APRN, FNP-BC, FNP-C, CEN, PHN, Haven Headache & Migraine Center
Peer reviewed by: Samantha Clem, PA-C, AQH, Haven Headache & Migraine Center
References
- American Migraine Foundation. What to Know About Allodynia. https://americanmigrainefoundation.org/resource-library/what-to-know-about-allodynia/
- Mínguez-Olaondo A, Quintas S, Morollón Sánchez-Mateos N, et al. Cutaneous Allodynia in Migraine: A Narrative Review. Front Neurol. 2022;12:831035. https://pmc.ncbi.nlm.nih.gov/articles/PMC8830422/
- Lipton RB, Buse DC, Nahas SJ, et al. Risk factors for migraine disease progression: a narrative review for a patient-centered approach. J Neurol. 2023;270(12):5692-5710. https://link.springer.com/article/10.1007/s00415-023-11880-2
- Ozarslan M, Matur Z, Tuzun E, Oge AE. Cutaneous allodynia and thermal thresholds in chronic migraine: The effect of onabotulinumtoxinA. Clin Neurol Neurosurg. 2022;220:107357. https://doi.org/10.1016/j.clineuro.2022.107357
- Chou TM, Lee ZF, Wang SJ, Lien CC, Chen SP. CGRP-dependent sensitization of PKC-δ positive neurons in central amygdala mediates chronic migraine. J Headache Pain. 2022;23(1):157. https://pmc.ncbi.nlm.nih.gov/articles/PMC9746101/
- Ashina S, Muenzel EJ, Nicholson RA, et al. Machine learning identifies factors most associated with seeking medical care for migraine: Results of the OVERCOME (US) study. Headache. 2024;64(8):1027-1039. https://doi.org/10.1111/head.14729
- Lipton RB, Burstein R, Buse DC, et al. Efficacy of erenumab in chronic migraine patients with and without ictal allodynia. Cephalalgia. 2021;41(11-12):1152-1160. https://doi.org/10.1177/03331024211010305
This article is for general education and is not medical advice. It is not a substitute for care from a qualified health professional. Always talk with your clinician before starting, stopping, or changing any treatment. If you have a sudden, severe headache, the worst headache of your life, or a headache with new symptoms like weakness, trouble speaking, or vision loss, seek emergency care right away.