One manufacturer says 633 nm, another says 660 nm, and both claim theirs is the right one. Is it worth worrying about?
The Short Answer
Not particularly. Both fall within the therapeutic red range, and both are absorbed by cytochrome c-oxidase. The 27-nanometer difference is much less important than the delivered dose.
If you are choosing between two devices solely based on this criterion, you are choosing incorrectly.
The Skin's "Optical Window"
Between approximately 600 and 1100 nm, the skin absorbs relatively little light — hemoglobin and melanin absorb more strongly below 600 nm, and water above 1100 nm.
Both 633 and 660 nm are within this window. Both reach the dermis, where fibroblasts are located.
The Real Differences
| 633 nm | 660 nm | |
|---|---|---|
| Penetration | Slightly shallower | Slightly deeper |
| History in studies | Often for skin indications | Often for scalp and muscles |
| Absorption by CCO | High | High |
The difference in depth is in the order of tens of micrometers. For practical purposes, it is negligible compared to differences in power between devices.
What Really Matters
- Delivered power in mW/cm² at skin level.
- Total dose — power multiplied by time.
- Coverage — is the entire face evenly illuminated.
- Distance — intensity decreases rapidly with distance.
- Regularity — see how often.
Each of these factors changes the outcome more than 27 nanometers.
How to Read Specifications
When a manufacturer emphasizes the exact wavelength but does not specify mW/cm², it usually means that power is not their strong suit.
The same applies to the number of diodes and the number of "colors." More in the selection guide.
Frequently Asked Questions
Which is better for wrinkles? Both work. The combination with infrared provides more than choosing between the two.
What about hair? For the scalp, 660 nm is more commonly used in combination with 850 nm. See Hair Loss and LED Therapy.
Why do some devices have both? A broader spectrum covers more absorption peaks. It's reasonable, but not a revolution.
Related articles
- Blue light 415 nm
- Mitochondrial biology of photobiomodulation
- Dr. Renú LED Face Masks
- Avci P et al. Semin Cutan Med Surg. 2013.
- Huang YY et al. Dose Response. 2009.
Sources
This article is for informational purposes only and does not substitute for medical advice.
