Cutaneous Allodynia: What Is It & What Can It Teach Us About Migraine?
In the midst of a migraine attack, have you ever found that brushing your hair, wearing jewelry, or putting on a blanket feels painful? You’re not alone. In fact, anywhere from 61% to 79% of migraine sufferers experience this sort of sensitivity during a migraine attack.
Yet before the year 2000, this migraine skin sensitivity, termed “painful hair syndrome” in the 18th century, and cutaneous allodynia in the 20th century, was largely misunderstood if not dismissed. Migraineurs were left to suffer needlessly, because they were reluctant to communicate their symptoms to physicians for fear of being told they were “crazy.”
Today, scientists understand that this common feature of migraine is not only very real, but can also provide important context for how best to treat individual cases of migraine or even individual attacks. In this article, we’ll explore the symptoms, physiology, and treatment of cutaneous allodynia. Plus, we’ll illuminate what it can tell you and your physician about your migraine.
What is cutaneous allodynia?
Cutaneous allodynia is skin hypersensitivity that accompanies a migraine attack in a large number of migraineurs. It is a perception of pain triggered by a stimulus that is generally not painful at all, such as routine contact with the skin or hair. Things like brushing your hair, the weight of a blanket, taking a shower, touching the skin around your eye, shaving, or wearing earrings might all feel painful or even unbearable during an attack, and often many hours after the attack has ended.
What causes cutaneous allodynia?
Cutaneous allodynia occurs because of a process called central sensitization. Input arriving from sensitized pain receptors that supply the meninges (the soft tissue that envelops the brain) causes the neurons that transfer pain signals to the brain to become more active and more sensitive. As a result of this increased sensitivity, the receptive fields of these neurons grow and extend beyond the original pain site. Once initiated, central sensitization can create signals of pain without external stimuli.
In migraine, it is believed that head pain and other symptoms are communicated via a pathway that involves the trigeminal nerves. Some researchers have theorized that in the case of cutaneous allodynia, first-order neurons in the trigeminal pathway transmit input to second-order neurons in the brain stem. In turn, these activate third-order neurons in the thalamus that transfer the pain signals to the cortex, which is the area of the brain that regulates many functions of the body, including sensory perception.
As migraine progresses along this neural pathway, sensitization of first-order neurons presents as throbbing head pain, which activates and sensitizes second-order neurons, leading to skin hypersensitivity in the head and face and muscle tenderness in the neck. In addition, the signals that are sent from the second-order neurons in the spinal cord to the third-order neurons in the thalamus sensitize the third-order neurons, which cause patients to feel as if their skin is hypersensitive and painful to touch all over their body. These migraineurs will avoid tight clothes, jewelry, heavy blankets, massages, or hugs.
What are risk factors for cutaneous allodynia?
Migraine With Aura
High Migraine Frequency
Migraine researchers have found that the prevalence of cutaneous allodynia increases in migraineurs with higher headache frequency. This sets up a chicken-or-the-egg scenario: Do repeated migraine attacks trigger the development of cutaneous allodynia? Or does cutaneous allodynia increase the frequency of migraine headaches once it develops? (We’ll get into more about this later in the article.)
Specific Migraine Symptoms
The likelihood of cutaneous allodynia more than doubles in migraineurs who experience symptoms of nausea, photophobia, and phonophobia. This is believed to be a result of common pathways shared in the development of these symptoms.
A 2013 study found that the ratio of female migraineurs with cutaneous allodynia was higher than the ratio of male migraineurs. Women are also more likely to experience migraine in the first place, which we know to be a common migraine statistic.
Research suggests that lifetime depression is an independent risk factor for the development of cutaneous allodynia.
Fibromyalgia is an autoimmune condition characterized by widespread pain, especially at specific points of the body. Generalized allodynia (pain that is felt throughout the body in the absence of stimuli to cause it), both in response to and independent of non-painful stimuli, is a defining feature of fibromyalgia. Studies show that as many as one out of every six migraine patients also suffers from fibromyalgia.
What does cutaneous allodynia treatment teach us about migraine?
The presence of cutaneous allodynia can give you and your physician important context about how to best treat your migraine and stop it from progressing over time. Two studies in particular are worth note and one even shows how cutaneous allodynia actually hinders migraine treatment protocols that were once widely accepted.
The timing of treatment matters.
Even if it’s not a part of your migraine treatment, you’ve likely heard of sumatriptan. This prescription drug belongs to a class of drugs known as triptans, which are used to quiet down overactive pain nerves that play a central role in the onset of migraine attacks. In 2004, Dr. Rami Burstein published a groundbreaking study establishing whether triptans could be used to stop the activation and sensitization of neurons that carry pain signals of migraine to the area of the brain where the perception of headache is generated. If so, such treatment could stop the progression of a migraine attack before the development of central sensitization and cutaneous allodynia.
To execute the study, Dr. Burstein treated with triptans two migraine attacks in patients experiencing cutaneous allodynia. In the first attack, sumatriptan was administered immediately after the onset of the attack (less than one hour), whereas in the second attack sumatriptan was administered two to four hours after attack onset. In the latter case, late intervention neither terminated migraine nor prevented the development of cutaneous allodynia. However, early treatment terminated the migraine headache within an hour without any development of additional pain or sensitivity.
This research was crucial because the FDA had approved sumatriptan for treating moderate to severe migraine attacks, rather than mild ones. So physicians would recommend a wait-and-see approach to triptan intervention and patients would not take their medicine until they were unable to bear the pain. Dr. Burstein’s research uncovered an important flaw in this philosophy: by the time a patient with cutaneous allodynia knows the migraine attack is severe, it’s likely too late for triptan intervention to be effective. Physicians now eliminate unnecessary suffering by recommending that sufferers take triptans within the first 20 minutes of a migraine attack.
Cutaneous allodynia is a predictor of chronic migraine.
Earlier in this article, we noted that cutaneous allodynia is more likely in migraine sufferers with higher headache frequency. While this was initially looked at as a chicken-or-the-egg scenario, a study published in the journal Brain shed new light on the potential role of allodynia in the development of increased headache frequency.
Researchers followed the progression of migraine in 2331 eligible participants over a period of six months or more. At the end of the study, they found that migraine frequency was more likely to have increased amongst the 70% of participants who had reported cutaneous allodynia. Thus, they concluded that cutaneous allodynia is a predictor of migraine chronification.
As a result, physicians understand that they may need to treat migraine patients who develop cutaneous allodynia more proactively, as migraine is more likely to become chronic in this population.
Could narrow-band green light be a source of relief?
Research shows that allodynia is reported more frequently during migraine attacks than between attacks. With this being the case, reducing the frequency of migraine attacks could in turn reduce episodes of cutaneous allodynia experienced alongside them. New research suggests that consistent narrow-band green light exposure shows strong potential to reduce the number of headache days per month in migraineurs — even those with chronic migraine..
These findings are supported by a 2020 study of 29 migraine patients, 22 of whom experienced chronic migraine. Over the course of 10 weeks, researchers exposed these participants to white-light-emitting diodes every day for a period of one to two hours. After a two-week rest period, the same participants were exposed to narrow-band green light daily over the course of another 10 weeks. During the green light exposure period, the number of headache days per month reduced by at least half in 63% of chronic migraineurs and 86% of episodic migraineurs.
Narrow-band green light is now available to everyone.
Regular exposure to narrow-band green light isn’t quite as simple as going to the hardware store and buying a green light bulb, since normal bulbs won’t emit the specific wavelength of light shown to reduce headache frequency and soothe migraine light sensitivity. Luckily, regular access to narrow-band green light is now easy thanks to The Allay Lamp. This patented lamp is portable, chargeable, and affordable, so you can take the soothing effects of narrow-band green light with you 24/7.
It has not only been shown to soothe migraine symptoms during an attack for many sufferers, it’s also easy to incorporate into your routine for daily exposure. The Allay Lamp is bright enough for reading and working, but can also dim at the touch of a button for bedtime use. Most importantly, it’s noninvasive, completely safe, and free of adverse side effects.