Key facts
- Chromophore
- Haemoglobin absorbs strongly around 577 nm; melanin absorbs across 532–1064 nm, falling as wavelength rises
- Yellow laser
- Around 577 nm, usually a long-pulsed solid-state or diode source; vessel-directed; not offered here
- Pulsed-dye laser
- 585–595 nm, as in Vbeam; vessel-directed, with bruising at some settings; not offered here
- Pico laser
- Picosecond pulses at 532, 785 or 1064 nm; pigment and ink, not vessels; used here as T2 Frax Radiance
- Used here for redness
- 675 nm 少女光 on the DEKA RedTouch Pro; R2 Glow long-pulsed 755 and 1064 nm for inflammatory redness
- Decided by
- The pressing-glass test and examination of what kind of redness it is
Why does the wavelength decide which laser treats redness?
Because each wavelength is absorbed mainly by one target. Post-inflammatory erythema, the flat red mark left after a pimple, is blood sitting in dilated capillaries, and so are the fixed redness and thread veins of rosacea. Oxygenated haemoglobin absorbs strongly around 577 nm, which is why yellow lasers sit there and pulsed-dye lasers sit close by at 585 to 595 nm: light absorbed by the blood heats the vessel wall until the vessel closes, while the skin around it absorbs comparatively little.
Melanin absorbs across a wide band from 532 nm into the near infrared, falling as wavelength rises. Pico lasers at 532 and 1064 nm were designed around that curve, and around pulses short enough to shatter pigment particles by a pressure effect rather than by heat. A vessel is not a particle. Closing it needs heat held in the wall for milliseconds, and a picosecond pulse does not deliver that, which is the physical reason a pico laser is the wrong tool for a red mark.
What does each laser do for PIE, rosacea flushing and acne redness?
For PIE, vessel-directed light is what the trial literature supports: pulsed-dye class lasers and intense pulsed light, delivered gently across a field of marks once the acne is controlled. A yellow laser works on the same principle at a neighbouring wavelength. A pico laser does nothing useful for the red mark and, if the mark is treated as if it were pigment, adds heat to skin that is already inflamed. The pressing-glass test in the PIE guide sorts the red mark from the brown one in seconds.
For rosacea, the vascular component responds to the same haemoglobin-directed wavelengths, but flushing is a neurovascular event rather than a fixed vessel, and no laser switches the condition off. The rosacea page explains why laser sits inside a medical plan of trigger review, barrier-respecting skincare and prescribed anti-inflammatory treatment rather than replacing it. Heat is itself a trigger, so energy is kept conservative.
Acne redness is two things at once: the inflammatory flush of active lesions and the PIE they leave behind. Active acne is controlled first, because new marks replace treated ones. Where the background is mainly inflammatory, Dr Sin Yong reaches for R2 Glow, a long-pulsed 755 and 1064 nm protocol directed at inflammatory activity; where redness, pores and texture occur together, the 675 nm 少女光 Laser on the DEKA RedTouch Pro, whose wavelength is absorbed by collagen and interacts with the vascular component of the dermis, is considered.
“Press a glass against the mark: if the red empties out, it's blood in vessels, not pigment in skin — and no brightening serum on earth treats a blood vessel.”
Dr Sin YongOn telling PIE from PIH
What do yellow and pulsed-dye lasers do differently from each other?
They share a target and differ in pulse, bruising and depth. Pulsed-dye lasers generate light in a liquid dye at 585 to 595 nm with adjustable pulse widths; at shorter pulses they can rupture the vessel and leave purpura, the purple bruising some settings produce, which clears but is visible for a time. Purpura-free settings exist, with a trade-off in how decisively a vessel closes. The comparison of Vbeam with other vascular lasers covers that decision in detail.
Yellow lasers at around 577 nm sit closer to the haemoglobin absorption peak and are usually delivered as longer pulses that heat the vessel without rupturing it, so bruising is less often part of the picture; the shorter wavelength also travels less far, which suits fine superficial vessels and diffuse redness more than larger blue vessels. Both are absorbed to some degree by epidermal melanin, so in Fitzpatrick III to V skin the settings and cooling matter, and darkening after treatment is the risk to plan around.
Yellow laser, pulsed-dye laser, pico laser and the 675 nm laser compared by target| Laser | Wavelength and target | PIE (red acne marks) | Rosacea redness and flushing | Here |
|---|
| Yellow laser | About 577 nm; haemoglobin | Vessel-directed; suits fine superficial vessels and diffuse redness | Fixed redness and fine vessels; does not stop flushing | Not offered here |
| Pulsed-dye laser | 585–595 nm; haemoglobin | Vessel-directed; purpura at some settings | Fixed redness and thread veins; does not stop flushing | Not offered here |
| Pico laser | 532, 785 or 1064 nm picosecond; melanin and ink | Not suited; pulses too short to close a vessel | Not suited to redness | T2 Frax Radiance, for pigment and texture |
| 675 nm 少女光 Laser | 675 nm fractional; collagen, with a dermal vascular effect | Considered where redness, pores and texture coexist | Vascular component, within a medical plan | DEKA RedTouch Pro, performed by Dr Sin Yong |
| R2 Glow | Long-pulsed 755 and 1064 nm; inflammatory activity | Where the background is inflammatory, once acne is controlled | Diffuse inflammatory redness | Performed by Dr Sin Yong |
Which wavelength does Dr Sin Yong use for redness, and why?
Facial redness here is treated with the 675 nm 少女光 protocol on the DEKA RedTouch Pro and, where the picture is mainly inflammatory, with R2 Glow; established individual thread veins are a separate target, with the wavelength chosen for vessel colour, depth and skin type at assessment. Yellow and pulsed-dye lasers are described on this page as devices other clinics use, not as something offered here.
The 675 nm wavelength is absorbed preferentially by collagen rather than water and works at the reticular dermis without ablating the surface, which is why it is chosen when redness coexists with enlarged pores, inflammatory acne or early laxity. Pico laser keeps its own job: discrete pigment, freckles and sun spots, and fractional texture work through the T2 Frax Radiance protocol. Sending a red mark to a pigment laser, or a brown mark to a vascular one, is the commonest way these treatments disappoint.
Who should wait, and what are the risks?
Treatment is deferred with active, uncontrolled acne, a recent tan or sunburn, photosensitising medication, infection in the area and in pregnancy. Steroid creams applied to the face can create a redness of their own that rebounds when they stop, and that is reviewed before any laser. Any mark that is raised, growing or bleeding is examined first rather than treated as redness.
The risks of vessel-directed light are bruising, blistering or crusting where energy is too high, darkening afterwards in melanin-rich skin, and, with repeated aggressive treatment, pale patches. Settings chosen for the skin, sun protection around treatment and conservative pacing are the safeguards. Dr Sin Yong assesses in person and sets the fee out in writing after the consultation; how fees are quoted explains what the quote contains.
