TL;DR: Q-switch lasers deliver ultra-short nanosecond pulses (5–20 ns) that fragment pigment particles photomechanically rather than thermally. Wavelengths: 532 nm (red/orange pigment), 694 nm Ruby (blue/black), 1064 nm Nd:YAG (deep pigment, safe in dark skin). Clinical use: solar lentigo, tattoo removal, café-au-lait, Nevus of Ota, melasma (low-dose). Picosecond lasers are the modern evolution.
How Q-switch works
The Q-switch mechanism compresses the laser pulse to 5–20 nanoseconds. This ultra-short pulse fragments pigment particles photomechanically — the particle is shattered, surrounding tissue is preserved. Macrophages then clear the fragments.
Wavelengths and use
| Wavelength | Target | Use |
|---|---|---|
| 532 nm (KTP, frequency-doubled Nd:YAG) | Red/orange pigment, hemoglobin, superficial melanin | Solar lentigo, red tattoo, telangiectasia |
| 694 nm Ruby | Blue/black pigment, deep melanin | Blue/black tattoo, Nevus of Ota, deep lentigo |
| 755 nm Q-switch Alexandrite | Green/dark blue pigment | Tattoo, low-dose melasma |
| 1064 nm Q-switch Nd:YAG | Deep pigment, safe in dark skin | All tattoos, dark-skin melasma, Nevus of Ota |
Indications
- Solar lentigo (age spots) — classic indication; one-session response common
- Tattoo removal — 6–12 sessions; wavelength matched to color
- Melasma — controversial; only low-dose sub-purpuric + topical hydroquinone + sun protection
- Café-au-lait — variable response, recurrence possible
- Nevus of Ota — 1064 nm standard; 6–12 sessions
- Post-inflammatory hyperpigmentation — control inflammation first, then low-dose Q-switch + topical
Skin types
| Fitzpatrick | Q-switch safety |
|---|---|
| I–II | Safe + efficient |
| III–IV | Safe with adjusted parameters |
| V–VI | 1064 nm only; test patch required; PIH risk highest |
Sessions
| Indication | Sessions | Interval |
|---|---|---|
| Solar lentigo | 1–2 | 4–6 weeks |
| Tattoo (black, professional) | 6–12 | 6–8 weeks |
| Tattoo (amateur) | 3–6 | 6–8 weeks |
| Café-au-lait | 4–8 | 6–8 weeks |
| Nevus of Ota | 6–12 | 2–3 months |
| Melasma (low dose) | 4–6 | 4 weeks |
Procedure
- Dermoscopic diagnosis. Suspect melanoma → biopsy, no laser.
- Test patch in first session
- Treatment: antiseptic prep, protective eyewear, spot-by-spot pulses
- Aftercare: cold compress, antibiotic ointment, SPF50+
- Follow-up: 4–8 weeks
Side effects
Expected: immediate frosting (white), mild redness 1–3 days, crusting 5–7 days (pigment), mild bruising. Less common: hyperpigmentation (PIH), hypopigmentation, transient purpura. Rare: scarring (keloid-prone), permanent pigment change, melasma flare (high dose), ocular injury without eyewear.
Contraindications
- Active sunburn or new tan
- Active herpes, acne nodules
- Keloid tendency
- Isotretinoin within 6 months
- Pregnancy / breastfeeding
- Suspected melanoma
- Active vitiligo
Q-switch vs picosecond
Picosecond lasers shorten the pulse to ~10⁻¹² seconds, generating even smaller pigment fragments with less thermal damage. Practical guidance: black/blue tattoo and solar lentigo respond well to Q-switch; multi-color tattoo + resistant melasma + dark skin lean picosecond.
FAQ
One session for spots? Often yes for solar lentigo; multi-session for others. Painful? Rubber-band snap sensation; topical anesthetic helps. Summer? Avoid — autumn/winter preferred. Dark skin? Only 1064 nm; PIH risk requires test patch and conservative parameters. Pregnant? No. Will spots come back? Treated spots don't return; new sun exposure creates new spots — SPF50+ for life.
Our clinic approach
- Dermoscopic diagnosis + AI skin analysis
- Wavelength chosen by Fitzpatrick type
- Test patch + informed consent + before/after photos
- 4–8-week intervals
- SPF50+ and topical protocol integrated
Conclusion
Q-switch is the first-line technology for pigment treatment. Right indication + right skin type + right wavelength deliver high success; wrong use risks PIH or permanent depigmentation. Always physician-administered in a certified clinic.
Dr. Murat Toktamısoglu, MD, PhD — Ataşehir, Istanbul. WhatsApp: +90 533 356 2480. Last medical review: May 18, 2026.
