Sequential Fractional CO and 1540/1570 nm Lasers: A Narrative Review of Preclinical and Clinical Evidence.

Ablative fractional CO laser is an established tool for dermatologic and aesthetic indications. Non-ablative wavelengths, such as 1540 and 1570 nm, are increasingly being combined with CO laser to optimise the results while reducing the recovery time. A narrative review of the literature was conducted, including ex vivo, in vivo, and in vitro studies, as well as human clinical trials that evaluated the efficacy, safety, and histological impact of dual-laser systems. Preclinical studies have shown that sequential application of fractional CO followed by 1540/1570 nm expands the thermal coagulation zone without increasing the ablation depth. At the histological level, the dual protocol promotes collagen remodelling with greater thermal precision. On a clinical level, a combined treatment has shown efficacy in improving scars, striae distensae, skin laxity, and wrinkles, with reduced recovery times compared to CO monotherapy. Preliminary data also suggest potential benefits in inflammatory conditions such as hidradenitis suppurativa. The sequential CO + 1540/1570 nm combination represents an effective and well-tolerated approach in regenerative dermatology. Current evidence supports its use as a versatile, safe, and reproducible technique for skin rejuvenation and scar modulation; however, further comparative studies are needed to standardise protocols.