The short answer: not well. Clothing absorbs, scatters and reflects most red and near-infrared light before it reaches your skin, so far less energy gets where it's needed. A thin, light-colored layer lets some near-infrared light through, but there's no way to tell how much, which turns your session dose into a guess. For consistent results, treat bare, clean skin.
What you'll learn
- Why fabric blocks red and near-infrared light
- How fabric type, color, thickness and layers change what gets through (quick reference table)
- What to wear during a panel, face mask or bed session
- Whether a longer session makes up for clothing
- Whether red light therapy works through glass
- How close you need to be, and whether skin contact matters
Why clothing blocks red light therapy
Red light therapy works by delivering a set amount of light energy to your skin and the tissue beneath it. That energy, measured in joules, is what our dosing guidelines are built around. Anything between the LEDs and your skin reduces it.
Fabric gets in the way in three ways:
- Absorption. Fibers and dyes soak up part of the light.
- Scattering. Light bounces between threads and spreads out, so less of it travels straight through to your skin.
- Reflection. Some light bounces off the surface of the fabric and never enters it.
Lab measurements show how much this adds up to. In a 2023 study of woven cotton fabrics, the samples reported in detail let through only about 10% to 37% of light between 770 and 950 nm, depending on the weave, density and dye. Even a single layer of cotton stopped most of the light (Dobnik Dubrovski et al., 2023).
What affects how much light gets through
- Fabric type and weave. Tightly woven, dense or thick fabrics block more. In a study using 850 nm near-infrared light, denim blocked the signal within two to three layers, while thinner cotton and polyester let a small, measurable amount through even when layered (Saleem et al., 2013).
- Layers. Each extra layer cuts the light further.
- Color. Dyes absorb visible light, so dark fabrics block more visible red light. At 850 nm near-infrared, color made only a small difference compared with fabric type (Saleem et al., 2013).
- Wet or dry. In the same study, damp fabric let more near-infrared light through than dry fabric. It still blocked a lot, so wetting your clothes isn't a workaround.
For more on the difference between the two types of light, see red light vs near-infrared.
Quick reference: what reaches your skin
| Between you and the light | What gets through | What to do |
|---|---|---|
| Nothing (bare skin) | All the light your device delivers at that distance | Best option for the area you're treating |
| Thin, light-colored cotton or linen | A fraction of the light, mostly near-infrared | Move it aside or uncover the area |
| Dark, thick or dense fabric (denim, fleece, wool) | Very little | Uncover the area |
| Several layers of clothing | Very little | Uncover the area |
| Sunscreen, makeup or heavy lotion | Less than bare skin | Treat clean skin and apply products afterward |
| Tinted or coated window glass | Can block much of the near-infrared | Don't use a panel through a window |
What to wear during red light therapy
The simple rule: uncover the area you're treating, and wear whatever you like everywhere else.
- Panels. Expose the area facing the panel. For a full-body session at home, many people wear underwear or nothing at all. Light won't reach covered skin, so any area under your underwear won't be treated.
- Face masks. Use a face mask on a clean face, without makeup or sunscreen. Tie back any hair that falls across your face.
- Beds. Wear as little as you're comfortable with. Underwear or a swimsuit is fine; the skin they cover just won't be treated. At a clinic or spa, follow their policy. See our red light therapy beds.
- Eyes. Wear protective goggles for the whole session. Goggles come with Rouge G4 panels and the Horizon bed, and the Elite face mask comes with eye covers. If your device doesn't include goggles, use a pair made for red light therapy.
- Bandages and dressings. Don't remove a dressing your healthcare provider applied in order to use red light therapy.
Can a longer session make up for clothing?
Not reliably. Your dose depends on how much light actually reaches your skin, and fabric changes that by an amount you can't measure at home. Doubling a session through a shirt might still leave you short, or it might not. It's simpler and more consistent to uncover the area and follow the session times in our dosing guidelines.
Longer isn't better, either. Our guidelines cap total exposure at 120 joules per session, adding up all the areas you treat, and no session should run longer than 20 minutes. For how often to do sessions, see how often should you use red light therapy.
Does red light therapy work through glass?
Glass is less of a barrier than fabric, but it still matters. Clear glass lets most visible red light through. Many modern windows are tinted or have a low-emissivity (low-E) coating designed to reflect infrared heat, and these can block much of the near-infrared light.
In practice, don't use a panel through a window, a glass table or a display case. Set it up so there's nothing between the LEDs and your skin.
Do you need skin contact?
No. Touching a panel isn't harmful, but it isn't practical, and panels are designed to be used at a distance. Our dosing guidelines use distances from about 15 cm (6 in) to 90 cm (36 in): closer for deeper tissue such as muscles and joints, farther for skin and larger areas. The closer you are, the more light reaches a smaller area, so sessions are shorter. Face masks sit close to the skin by design.
For more setup tips, read 10 mistakes to avoid with red light therapy at home.
Frequently asked questions
Does red light therapy work through clothes?
Not well. Clothing blocks most red and near-infrared light, so much less reaches your skin. For consistent results, treat bare, clean skin.
Does near-infrared light go through clothing better than red light?
Somewhat. Near-infrared light is less affected by fabric color than visible red light, but fabric still absorbs and scatters most of it, especially when it's thick or layered.
Can you wear underwear during red light therapy?
Yes. The skin under your underwear won't be treated, but the rest of your session works as normal.
Do you have to be naked for red light therapy?
No. Only the area you're treating needs to be uncovered. For full-body sessions, many people wear underwear or nothing, whichever they prefer.
What should you wear in a red light therapy bed?
As little as you're comfortable with. Underwear or a swimsuit is fine. Wear protective goggles for the whole session.
Does red light therapy work through glass?
Partly. Clear glass lets most visible red light through, but tinted or coated windows can block much of the near-infrared. Keep glass out of the way during sessions.
Sources
- Dobnik Dubrovski P, Fakin D, Ojstršek A. Cotton woven fabrics as protective polymer materials against solar radiation in the range of 210–1200 nm. Polymers. 2023;15(5):1310. MDPI
- Saleem A, Canal C, Davis LAJ, Green RJ, Hutchins DA. Near infrared transmission through various clothing fabrics. Journal of Textile Science & Engineering. 2013;3(2):129. Full text
This content is for educational purposes only and is not a substitute for professional medical advice. Consult your healthcare provider before starting any new treatment, especially if you have a medical condition, take photosensitizing medication or are pregnant.