Laser Resurfacing: CO2 vs. Erbium
The physics of water absorption in human tissue dictates the severity, downtime, and outcome of ablative lasers.
Mechanism of Action
Ablative lasers work by targeting water as their primary chromophore. Because the epidermis is approximately 70% water, these specific wavelengths of light are rapidly absorbed, superheating the intra- and extra-cellular water until the tissue vaporizes (ablates).
The Two Primary Ablative Wavelengths
- CO2 (10,600 nm): Extremely high water absorption, but leaves a zone of thermal coagulation (heat damage) around the vaporized tissue. This heat causes immediate collagen contraction and significant long-term neocollagenesis. High downtime (7-14 days).
- Erbium:YAG (2,940 nm): Has an absorption coefficient in water 16 times greater than CO2. It vaporizes tissue so quickly that very little residual heat is transferred to surrounding areas. Less collagen contraction, but much faster healing (3-7 days).
Fractionated Delivery
Historically, lasers ablated 100% of the surface area (fully ablative), leading to weeks of raw, weeping skin and high risks of scarring and hypopigmentation. Modern devices are almost exclusively "fractionated"—they drill microscopic columns of thermal damage (Microthermal Treatment Zones, or MTZs) leaving islands of healthy tissue intact to speed epithelialization.
Clinical Outcomes Matrix
| Modality | Target Condition | Downtime | Fitzpatrick Risk |
|---|---|---|---|
| Fractional CO2 | Severe rhytids, Deep acne scars | 7-10 Days | High (Types IV-VI) |
| Fractional Erbium | Superficial texture, Fine lines | 4-7 Days | Moderate (Types IV-VI) |
| Non-Ablative (1565nm) | Mild texture, Pigment, Maintenance | 1-3 Days | Low |
FAQ
- Does laser resurfacing thin the skin?
- Temporarily during the ablation phase, yes. However, the subsequent wound healing response deposits new, highly organized collagen and elastin, ultimately resulting in thicker, more resilient dermal architecture.
- When will I see results?
- Epidermal (surface) healing occurs in 1-2 weeks. However, true dermal neocollagenesis begins around week 3 and peaks at months 3-6. Final results cannot be judged before 6 months post-procedure.