March 31, 2026 Jacky Chan

Herniated (Slipped) Disc and Red Light Therapy: What the Research Says So Far

This article is for general education and isn't medical advice. Talk to your doctor or physical therapist before starting any new therapy, especially if you have a diagnosed condition, are pregnant, or take medications that increase light sensitivity.

A herniated disc, often called a slipped or bulging disc, is one of the more common reasons people end up with back pain that travels down a leg. It's also a topic where a lot of red light therapy marketing gets ahead of the evidence. As a certified personal trainer, stretch therapist and massage therapist, I spend a lot of time with people who are working on recovery and movement, so I want to lay out plainly what a herniated disc is, what red and near-infrared light therapy is, and what the research does and doesn't show so far.

What a Herniated Disc Is

Your spine is a stack of bones (vertebrae) with rubbery discs between them. According to Mayo Clinic, each disc has a soft, jellylike center inside a tougher outer ring. A herniation happens when some of that softer material pushes out through a tear in the ring. It can happen anywhere in the spine, but it is most common in the lower back.

When the disc material irritates a nearby nerve, people may feel pain in the buttock, thigh, calf or foot, along with numbness, tingling or weakness. Mayo Clinic also notes that some people with a herniated disc have no symptoms at all and only find out from an imaging test. In other words, what shows up on a scan and what you feel don't always line up, which is one more reason a proper evaluation matters.

When to get help right away

Mayo Clinic advises calling your healthcare professional if neck or back pain spreads into an arm or leg, or if you notice numbness, tingling or weakness. It recommends seeking immediate care for:

Pain, numbness or weakness that keeps getting worse and makes daily activities hard
Trouble controlling your bladder or bowels
Numbness in the inner thighs, around the rectum or other "saddle" areas

No device, red light therapy included, should delay that kind of care.

What Red Light Therapy (Photobiomodulation) Is

Red light therapy uses low levels of red and near-infrared light. The research term is photobiomodulation, or PBM. Older studies often call it low-level laser therapy (LLLT), because many early trials used lasers rather than LEDs. Cleveland Clinic describes red light therapy as thought to work by acting on mitochondria, the energy-producing parts of your cells.

It's worth being clear about the limits from the start. Cleveland Clinic lists pain and inflammation among potential uses that researchers are still investigating, and says there isn't enough evidence yet to support most uses. For more background on the technology itself, see our red light therapy 101 guide.

Can the Light Reach a Spinal Disc?

This is the first honest question to ask. Lumbar discs sit deep in the body, behind skin, fat, thick back muscles and bone. A 2017 computer-modelling study in Lasers in Medical Science found that longer wavelengths travel deeper into skin than shorter ones, but the modelled penetration depths were measured in millimeters, not inches. That doesn't mean no light travels further, but it does mean that claims about a home device delivering a meaningful dose "to the disc" are not something the research has shown.

What the Research Shows So Far

Lab studies on disc cells

Some of the interest comes from cell research. In a 2018 study in Scientific Reports, researchers took disc cells removed during spine surgery, exposed them in a dish to inflammatory signals, and then to red, green or blue light at several doses. Some combinations lowered levels of enzymes involved in breaking down disc tissue, and the effects varied by wavelength and dose. This was cell-culture work only, so it tells us about possible mechanisms, not about results in people.

Clinical trials in people with disc-related pain

A 2022 randomized trial of 110 adults with low back pain and leg symptoms coming from a disc (discogenic lumbar radiculopathy) compared low-level laser therapy plus conventional physical therapy with physical therapy alone. Both groups had 18 sessions. The authors reported statistically significant differences in pain, disability and range of motion between the groups and described laser therapy as an efficient add-on to physical therapy. Because the comparison group received physical therapy alone, it's hard to separate the effect of the light from the effect of simply receiving an extra treatment.

A 2023 systematic review and meta-analysis in Perspectives on Integrative Medicine pooled five randomized trials (845 patients) of low-level laser therapy for lumbar disc herniation. Compared with inactive or sham treatment, laser groups had better pain and disability scores, and laser added to usual care did better than usual care alone. But laser on its own was not more effective than usual care, the certainty of the evidence was rated low to very low, and the authors called for larger, well-designed trials.

The broader low back pain picture

Many people with back pain don't have a confirmed disc herniation, so the general low back pain research is worth knowing too. A 2021 placebo-controlled trial published in Pain randomly assigned 148 adults with chronic non-specific low back pain to real or placebo photobiomodulation, 12 sessions over four weeks, with patients, therapists and assessors all blinded. The researchers found no clinically important difference in pain or disability between the groups. No adverse events were reported.

Putting it together

The honest summary: red and near-infrared light is being studied for disc-related back pain. A small number of trials have reported positive results, mostly when light was added to physical therapy, while a carefully blinded placebo-controlled trial in general low back pain found no meaningful benefit. That's an early, mixed evidence base, not a settled answer, and the studies used clinic-based laser or light devices, so their results don't tell you how a particular home device will perform.

What Matters First: Diagnosis and a Plan

If you have back pain that radiates into your leg, start with a doctor or physical therapist who can examine you and rule out anything that needs urgent attention. They can help you build a plan, which may include activity changes, specific exercises and other options. Red light therapy is not a substitute for that evaluation or for medical treatment.

From a trainer's point of view, the general principles I care about with anyone whose back is sensitive are simple: stay as active as your clinician says is appropriate, build up gradually, and don't push through sharp or worsening nerve symptoms. The specific exercises for a disc problem should come from your physical therapist, because what's right for you depends on your exam and history.

If You're Considering Red Light Therapy at Home

If you and your clinician decide a home device is reasonable to try, keep these points in mind:

Follow the manufacturer's instructions for session length, distance and frequency. There is no established dose of light for disc-related pain.
Protect your eyes. Cleveland Clinic advises shielding your eyes when using at-home devices.
Check with your doctor first if you're pregnant, have a light-sensitive skin condition, or take medications that increase light sensitivity.
Don't use it to cover up symptoms. New or worsening numbness, weakness, or bladder or bowel changes need medical attention, not another session.
Keep expectations realistic. Cleveland Clinic says red light therapy appears safe when used short-term and as directed, but notes that the long-term safety of these devices isn't yet known.

If you'd like to see what at-home devices look like, you can browse our red light therapy collection. We're glad to answer questions about a device's specs, but questions about your back belong with your doctor or physical therapist.

Sources

Written by Jacky Chan, certified personal trainer, stretch therapist and massage therapist, and founder of Peak Flow Fitness. Have a question about the equipment in this guide? Contact our team.

Filed in: back pain, herniated disc, photobiomodulation, recovery, red light therapy, slipped disc

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