Infrared light 830–850 nm—how deep does it penetrate

If you turn on the infrared mode and the mask appears off, everything is fine. This is the most common question about this spectrum.

Why it's not visible

The human eye sees approximately up to 700 nm. Light at 830 or 850 nm is outside this range — it's there, but you can't see it.

Many devices include a dim visible diode as an indicator to let you know the mode is working. If yours doesn't — check with your phone's camera. Most sensors register near-infrared as a pale purple glow.

How deep does it penetrate

Near-infrared light penetrates deepest of all wavelengths used in LED therapy — approximately up to about 5 mm into soft tissue.

This makes it the only part of the spectrum that reliably reaches the lower dermis and the dermal papilla of the hair follicle. That's why it's standard for scalp devices — see Hair Loss and LED Therapy.

What it does there

Stimulates mitochondria — the same mechanism as red light, but deeper.
Anti-inflammatory effect in deeper layers.
Supports microcirculation.
Participates in recovery after procedures — see wound healing.

Heat — an important clarification

Infrared light is often confused with thermal radiation. These are different things.

Near-infrared (around 800–900 nm) at therapeutic doses does not noticeably heat the skin. Far-infrared — like what an infrared sauna emits — is something entirely different.

If you feel a noticeable warming from an LED mask, it's usually from the electronics, not from the therapeutic effect. For rosacea, this matters — see the separate article.