Red light therapy (also called photobiomodulation, low-level light therapy, or LLLT) is shining red and near-infrared light on your skin to drive cellular changes underneath. Most people use it for skin (firmer, less wrinkles, less acne, faster healing), hair regrowth, and faster recovery from training. A smaller group uses it for thyroid issues, mood, sleep, joint pain, and fertility.

It's not a stimulant or a drug. The light penetrates a few centimetres into tissue, gets absorbed by your mitochondria, and nudges them to produce more energy and less inflammation. The effects are real but cumulative and modest. You're not going to feel anything after one session. You'll see things change over weeks of consistent use. Done at the right dose it has almost no downside, the catch is that dose, wavelength, distance, and consistency all matter and most people get them wrong.

Deep-dive

Dosage:

• Wavelengths: Red (630-670 nm, with 660 nm the most studied) for skin, hair, superficial tissue. Near-infrared (810-850 nm) for muscle, joint, thyroid, brain, deeper tissue. A combined 660+850 nm panel covers most use cases
• Dose at target tissue: 3-10 J/cm² for skin, 10-60 J/cm² for deeper tissue. More is not better, the response is biphasic. A typical panel at 6 inches delivering 100 mW/cm² hits 6 J/cm² in 60 seconds, so most skin sessions are 1-3 minutes per area, not 20
• Distance: 6-12 inches from the body for most panels. Closer is not better, the intensity rises sharply but you risk overdosing and heating tissue. Check your specific device's irradiance curve
• Session length: 5-20 minutes total covering the areas you care about, 3-5 times per week. Sessions over 20 minutes are rarely doing more than the first 10. Daily is fine if the per-session dose is moderate; if you're running high power close to the skin, every other day is enough
• Skin and anti-aging: Face or specific area at 6-12 inches, 1-3 min per area, 3-5x/week. Expect changes at 6-12 weeks.
• Hair (AGA): Scalp coverage, 10-15 min, 3x/week. Consistency matters more than session length. Most clinical trials ran 24-26 weeks before evaluating
• Muscle recovery/performance: Apply 30-60 min before training or immediately after, 3-10 min per major muscle group at 6-8 inches. NIR (810-850 nm) penetrates deeper, use it for muscle, not red alone
• Thyroid (Hashimoto's): Front of the neck over the thyroid, 5-10 min, 2-3x/week. The Höfling protocol used 830 nm, so NIR is the wavelength of interest here. Don't expect to drop levothyroxine without monitoring TSH/T4 alongside, this is a "do it and watch your labs" application
• Transcranial (cognition/mood): This is where dosing gets touchy and home devices are inconsistent. 810 nm at 100-200 mW/cm² for 8-20 min to the forehead in published trials. If you're doing this for depression rather than for fun, do it with a clinician who's tracking it
• Eye protection: Wear blackout goggles for face/scalp work, especially at higher power. Red light isn't directly damaging the retina the way UV would, but bright NIR at close range over time isn't well studied for ocular safety. Cheap goggles included with most panels are sufficient. Just close your eyes and look away isn't enough at close range
• Timing of day: Morning or daytime is generally preferred. Some people get mild alertness afterward which can disrupt sleep if done late

Here's what you can expect:

For skin, expect subtle improvements in tone, texture, and hydration at 2-4 weeks, more visible reductions in fine lines and overall skin quality at 8-12 weeks. The change is real but gradual, more "I look better-rested" than "I look 10 years younger." For hair, no visible change for 8-12 weeks, then a slow reduction in shedding and gradual fill-in in thinning areas over 4-6 months. For muscle recovery, you may notice less soreness the day after a hard session within the first week or two of using it pre-workout. For Hashimoto's, lab markers (TSH, antibodies) shift over months, not weeks, and you'll want bloodwork to confirm rather than relying on subjective feel. For cognition and mood, effects are subtle and individual, some people notice a clearer feeling after sessions, others nothing.

The biggest mistake people make is inconsistency. Three sessions and quitting will do nothing. Three sessions a week for three months will do something. The second biggest mistake is overdoing it: longer sessions or closer to the skin past the optimal dose start eroding the benefit.