Science Behind Red Light Therapy for Neuropathy Pain

Have you ever wondered what light can do for your health? Red light therapy has gained traction in recent years due to its potential ability to promote skin health, hair growth, wound healing, and other proposed benefits. But can red light therapy also relieve pain due to neuropathy? Research suggests this may be so.

Does red light therapy help with neuropathy?

Red light therapy (RLT) is a type of alternative therapy that applies light with low wavelengths (600–750 nm) to the body for the management or potential treatment of health conditions. It falls under the umbrella term of low-level light therapy, which also includes light in the near-infrared range (750–1,400 nm). Higher wavelengths of light penetrate tissues more deeply than lower wavelengths. For this reason, near-infrared light is used to manage conditions affecting deeper structures such as muscles and nerves, while red light targets more superficial structures such as the skin.

Research studies have employed both red light and near-infrared light for the management of neuropathy, a condition that affects 2.4% of the world’s population. Neuropathy, or nerve pain due to nerve damage, can be a result of many different underlying conditions, most commonly diabetes. Some other causes include medications, toxins, or injuries.

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In research studies, RLT has been used to address different types of neuropathies, including diabetic neuropathy, chemotherapy-induced neuropathy, orofacial neuropathy, and more. However, studies have used inconsistent parameters for light delivery, including area of irradiation, light energy density, wavelength, and number and duration of treatments. Therefore, there is no standard protocol for using RLT to treat neuropathy and no conclusive evidence that certain parameters work better than others.

How does red light therapy work for neuropathy?

Since near-infrared light targets the nerves better than red light, most studies on RLT and neuropathy have utilized wavelengths in the near-infrared range. For therapeutic purposes, red light and near-infrared light are often combined in RLT devices.

RLT devices, which can take the form of lasers or LEDs, emit photons that are absorbed by cells and cause metabolic changes. Although the research is evolving, evidence from animal studies suggests that RLT works by stimulating a molecule called cytochrome c in mitochondria, leading to increased production of cellular energy. RLT also causes mild oxidative stress leading to the production of antioxidants and anti-inflammatory molecules. These and other mechanisms might promote nerve healing and prevent further nerve damage.

Many rodent studies utilize a technique in which the sciatic nerve (a major nerve in the body) is injured to induce neuropathic pain. These studies have consistently shown the pain-reducing effect of RLT. One study suggests that the shift in immune cell profile from pro-inflammatory to anti-inflammatory is a potential pain-reducing mechanism.

Some notable animal studies include the following, most of which used laser sources of light:

• In a 2020 study, researchers found that red light applied daily over 7 days significantly reduced neuronal cell death and pain in rats compared to those that did not receive RLT.
• A 2014 study in rats showed that both red and near-infrared laser light increased pain tolerance after 2 weeks of treatment following sciatic nerve injury compared to rats that did not receive light therapy. In this study, red light (660 nm) was associated with better therapeutic effects than near-infrared light (980 nm).
• A 2012 study in rats with sciatic nerve injury found that red light reduced inflammatory markers and increased the number of proteins that may promote nerve regeneration after 7 days of treatment.
• In a 2010 study, rodents with sciatic nerve injuries were exposed to red light daily for 3 weeks. Compared to the control group, exposed rodents increased antioxidant levels and produced molecules responsible for accelerating the growth of nerve axons (structures that transmit electrical pulses).

Benefits of red light therapy for neuropathy

Although results are mixed, neuropathic pain has generally shown a positive response to light therapy in clinical (human) studies. However, due to the lack of protocol consistency across studies, further research is needed to clarify the optimal parameters and duration of treatment.

Research suggests that the benefits of light therapy for neuropathy primarily involve improvements in pain. Studies have shown benefits ranging from the immediate post-treatment period up to several months after treatment, although long-term studies are lacking to determine whether continued treatment is needed for sustained pain relief.

While there is no clinical evidence that RLT can reverse the underlying cause of neuropathy, animal models have shown that light therapy may accelerate the process of nerve regeneration, increase the number of myelinated nerve fibers, promote a healthier myelin sheath (the coating around nerves), and cause the release of growth factors.

Diabetic neuropathy

Neuropathy is seen in up to 40.3% of people with diabetes. High blood sugar levels affect the blood vessels that supply the nerves in the hands and feet, leading to nerve damage over time. This can lead to pain, burning, numbness, and a pins-and-needles sensation.

An older 2004 study showed that subjects with diabetes had similar pain reductions after a 4-week period of receiving either near-infrared laser light therapy or sham therapy. The authors concluded that their study did not provide sufficient evidence to recommend light therapy for painful diabetic neuropathy.

This study, however, stands alone. Most other studies have shown a beneficial response of diabetic neuropathy to red or near-infrared laser light. Some examples include the following:

• In a 2019 study of older adults with painful diabetic peripheral neuropathy, treatment with near-infrared light over a 12-week period led to significantly lower pain levels and improved quality of life compared to individuals who received sham treatment.
• A 2012 study showed that subjects with diabetes treated with near-infrared light demonstrated significantly reduced pain and improved foot skin microcirculation after a 4-week treatment period compared to the control group.
• Researchers of a 2011 study applied near-infrared light to people with diabetes 3 times a week. After 10 sessions, subjects showed a significant increase in neural potential amplitudes detected in a nerve conduction study, reflecting an improvement in nerve health.

Chemotherapy-induced neuropathy

Chemotherapy used to treat cancer can have toxic effects leading to nerve damage. Few studies have evaluated the use of light therapy for the management of chemotherapy-induced neuropathy.

• A 2023 study revealed that 48% of patients with chemotherapy-induced neuropathy had improvements in their pain at the end of a 6-week treatment period with laser RLT. These improvements were sustained at 6 weeks following the completion of treatment.
• A 2017 study found that patients who underwent near-infrared light therapy experienced significant reductions in chemotherapy-induced neuropathic pain at 4, 8, and 16 weeks compared to those who received sham treatment.
• In a 2022 study of breast cancer patients, treatment with near-infrared light prevented the worsening of neuropathy compared to patients in the control group throughout their course of chemotherapy.

Neuropathic orofacial pain

Neuropathic orofacial pain describes a number of clinical syndromes that can cause nerve-related pain in the face and mouth. One type of neuropathic orofacial pain is trigeminal neuralgia, characterized by severe pain in the distribution of the trigeminal nerve on one side of the face. Another type is burning mouth syndrome, in which patients have ongoing or recurring burning in the mouth without a clear cause.

• A 2012 study showed that patients with trigeminal neuralgia (facial pain due to nerve damage) had significantly lower pain up to 6 months after treatment with near-infrared light plus ganglion block (medical procedure using injections) compared to patients who received ganglion block only.
• A 2017 study revealed that patients with trigeminal neuralgia and burning mouth syndrome experienced improvements in pain after 4 weeks of treatment with either red light or near-infrared light, although near-infrared light led to greater pain reductions.
• In a 2011 study, patients with burning mouth syndrome had improvements in pain immediately after each weekly session of RLT over a 10-week period. However, this study lacked a control group.

Carpal tunnel syndrome

Carpal tunnel syndrome is a condition in which the median nerve gets compressed as it travels through the wrist, leading to numbness, tingling, and pain in the hand and forearm.

Studies on the effectiveness of light therapy for carpal tunnel syndrome are mixed.

A 2014 study showed a significant reduction in pain among patients with carpal tunnel syndrome who received near-infrared light therapy compared to those who received sham treatment for a total of 20 sessions. By contrast, a 2012 study showed no benefit, although this study employed fewer treatment sessions and a lower energy of light per session.

Red light therapy devices for neuropathy

RLT can be administered either via lasers or LED sources. LED sources represent the vast majority of RLT devices on the market for use at home (as they are less expensive), while lasers are typically used in specialty clinics and in research studies (as they require more technical skill).

Animal studies have shown that laser and LED sources are both effective for a variety of indications. Some human studies suggest that laser and LED have comparable effectiveness in the treatment of certain conditions such as dental pain and surgical wounds. However, the quality of these comparisons is low, and not all studies have reached the same conclusion.

No studies have compared the effectiveness of laser versus LED on neuropathy. Therefore, it remains to be determined which of these modalities is better. If you can afford it, the best outcomes are likely to come from receiving professional treatment at a specialty clinic utilizing laser therapy, as the depth of light penetration can be better controlled.

If you decide to try at-home RLT devices, many options exist on the market. In particular, boots, slippers, and foot massages with LEDs can be worn or used if you have neuropathy in your feet, which is the most common location.

Side effects and precautions of using RLT for neuropathy

RLT, including both red light and near-infrared light, is considered very safe due to its high wavelength and low energy. These types of light are considerably weaker than ultraviolet light coming from the sun or used in tanning beds.

While RLT devices used in clinical studies are generally safe, with few adverse effects reported, the safety of commercially available RLT devices for home use is not well-established. In unusual cases, localized itching, dryness, swelling, redness, burns, or blisters may occur. The risk is increased in individuals with neuropathy, who have decreased sensation in their extremities and may not notice adverse effects. The risk is further heightened for individuals who wear an RLT device for a prolonged period of time (typically longer than 30 minutes), which may lead to device malfunction.

The greatest risk of using RLT for neuropathy is that it becomes a replacement for medical therapy. No RLT device can replace the judgment of a qualified medical professional who can evaluate your condition and potentially help reverse the underlying cause. For example, if your neuropathy is due to a vitamin deficiency, correcting the deficiency should be the priority. RLT should only be used as an adjunct to medical therapy, not a substitute.

Comparison of red light therapy with other neuropathy treatments

RLT is one of several options for the management of neuropathy. Some other common treatments are included in the following table.

*Price ranges per treatment course/device, taken from Amazon and GoodRx.

While red light therapy might be a promising option for people with neuropathic pain, near-infrared light (often included in red light therapy devices) has been more extensively studied. Further research is needed to determine the optimal protocol for red light therapy. Consult with your doctor prior to beginning any new treatments to ensure that red light therapy only accompanies — but does not replace — medical treatment for neuropathy.