Allodynia: Causes, types, and treatment
Allodynia can be a symptom of several different nerve conditions, or it can occur on its own.
Allodynia is not the same thing as an increased response to painful stimuli.
Some people feel extreme pain from something minor, such as a paper cut. Feeling increased pain or being hypersensitive to mild pain is called hyperalgesia.
Individuals with allodynia, however, feel pain when something is ordinarily painless.
Pain is one of the body's protective mechanisms. It tells a person to stop doing something that is harmful.
For instance, a pain response causes a person to pull their hand away from a hot stove, preventing a severe burn. But people with allodynia perceive pain even though there is nothing harmful causing the pain.
The main symptom of allodynia is pain from non-painful stimuli.
Some people with allodynia may experience severe pain even from a few hairs brushing against their skin.
Symptoms can vary from mild to severe. Some people may feel a burning sensation while others feel an ache or squeezing pain.
Allodynia can limit the activities a person is able to do and decrease their quality of life. Common complications of allodynia include:
Types of allodynia
There are three main types of allodynia, which are classified according to what causes the pain.
Regardless of the type of allodynia, pain is still the main symptom. Some people may only have one type of allodynia. Others may have all three types of the condition.
Types of allodynia include:
- Thermal allodynia: Thermal allodynia causes temperature-related pain. Pain occurs due to a mild change of temperature on the skin. For example, a few drops of cold water on the skin may be painful.
- Mechanical allodynia: Movement across the skin causes mechanical allodynia. For instance, bedsheets pulled across a person's skin may be painful.
- Tactile allodynia: Tactile allodynia, also called static allodynia, occurs due to light touch or pressure on the skin. For example, a tap on the shoulder may cause pain for someone with tactile allodynia.
Causes and risk factors
Something as simple as hair being brushed may cause intense pain to someone with allodynia.
The exact cause of allodynia is not known.
Allodynia may occur due to increased responsiveness or malfunction of nociceptors, which are a particular type of nerve.
Having one of the following medical conditions may also increase a person's risk of developing allodynia.
- Migraines: Migraines can cause debilitating head pain, but a headache is often not the only symptom. Migraines can also cause additional symptoms, such as nausea and sensitivity to sound and light. According to the American Migraine Foundation, up to 80 percent of people experience symptoms of allodynia during a migraine.
- Postherpetic neuralgia: Postherpetic neuralgia is a complication of shingles, which is caused by the same virus that causes chicken pox. Shingles can cause damage to the nerve fibers, which leads to persistent nerve pain and is associated with allodynia.
- Fibromyalgia: Fibromyalgia is a medical condition that causes widespread pain in the body. The cause of fibromyalgia is not known, but there does appear to be a genetic link in some instances. There also seems to be a connection between allodynia and fibromyalgia.
- Diabetes: Over time, diabetes can cause damage to nerves, increasing the likelihood that a person will develop allodynia. Nerve growth factor (NGF) is essential to the nervous system, and some experts have suggested that diabetes can lower NGF levels. A recent study in rodents showed that low levels of NGF led to both hyperalgesia and allodynia.
- Complex regional pain syndrome: Complex regional pain syndrome (CRPS) is a long-term pain condition that tends to affect one limb, typically after the person injures the area. People believe CRPS occurs due to problems with the nervous systems.
Diagnosis and when to see a doctor
There is not one specific medical test to diagnose allodynia. Instead, a doctor will perform a physical exam, take a medical history, and review a person's symptoms.
Many common conditions can cause chronic pain, so doctors may need to rule out certain medical conditions before they can make a diagnosis of allodynia.
Various nerve sensitivity tests may also be performed to help make a diagnosis.
Anyone who experiences pain from non-painful stimuli, such as light touch, should see their doctor.
Dealing with chronic pain that develops after even the mildest touch can be frustrating and upsetting. Receiving an accurate diagnosis can help someone start the treatment and management process.
Topical creams may help to treat the symptoms of allodynia. Recommended treatment will be based on the cause of the condition.
Currently, there is no cure for allodynia. Treatment is aimed at decreasing pain, using medications and lifestyle changes.
Pregabalin is a medication used to treat nerve pain associated with conditions, such as spinal cord injuries, diabetes, fibromyalgia, and shingles. It may also decrease pain in some people with allodynia.
Topical pain medications, such as creams and ointments containing lidocaine, may be helpful in some cases. Over-the-counter, non-steroidal medicines may also be effective.
Complementary approaches to pain management, such as acupuncture and massage, may not be tolerated as they involve touch and can lead to discomfort for a person with allodynia.
Treating an underlying condition that is causing allodynia may also help. For example, preventing migraines or treating migraines straightaway can help reduce the risk of allodynia symptoms. Getting diabetes under good control can also be helpful.
Some people might find that lifestyle changes, such as light exercise, a healthful diet, and getting enough sleep might help.
Although living a healthful lifestyle will not cure allodynia, it can enhance overall health and help people with the condition cope more efficiently.
Identifying and decreasing pain triggers as much as possible may also reduce symptoms. It may not be possible to limit all the things that cause discomfort, but some changes may help.
For example, it might not be reasonable for someone to shave their head if brushing their hair hurts. But switching to a different type of brush or brushing it less frequently may be possible.
Similarly, if certain fabrics hurt the skin, a person can try clothing made of a different, less irritating material.
Stress may make the pain worse in some people. So, learning stress management techniques may also help.
Although stress reduction may not improve allodynia in every case, developing better stress management techniques can help a person cope with their condition.
Allodynia is not life-threatening, but it can make daily life difficult and cause frustrating limitations. It can also lead to anxiety and other mental health conditions.
The outlook for people with allodynia varies depending on the severity of the condition. Taking a comprehensive approach to treatment can improve the outlook.
Using a combination of pain management techniques along with lifestyle changes may decrease symptoms of allodynia.
A holistic approach can also help someone feel more in control of their condition and improve their overall quality of life.