Rosacea remains a therapeutically challenging, chronic facial dermatosis whose central feature-persistent erythema-often resists topical and systemic agents. In this study we evaluated, for the first time, the simultaneous use of a 532-nm potassium titanyl phosphate (KTP) laser and a microsecond-pulsed 1064-nm Nd:YAG laser as a safe alternative.

Rosacea is an extremely common condition characterised by facial flushing, dilated capillaries and papules and pustules. Both systemic and topical treatments have their drawbacks, such as limited efficacy, intolerable adverse reactions, drug resistance and high recurrence rates. Therefore, it is necessary to explore new treatment methods for rosacea.

Lasers have been used for more than three decades to treat vascular lesions with an excellent safety profile and very low risk of scar formation. Purpura was a common side effect of the previous generation of lasers and has been significantly reduced with the introduction of newer devices. The 532-nm potassium titanyl phosphate (KTP) laser is used for treating vascular cutaneous lesions due to its selective absorption by haemoglobinn, while rarely inducing purpura. However, the 532-nm KTP laser is primarily effective for superficial blood vessels. The long-pulsed 1064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser can penetrate up to 4-6 mm beneath the skin and is effective in treating larger blood vessels. Previous studies have demonstrated that the long-pulsed 1064-nm Nd:YAG laser is effective for both erythematotelangiectatic rosacea (ETR) and papulopustular rosacea (PPR). However, traditional millisecond-domain devices should still be used with caution in darker skin types, and it is associated with an extensive zone of thermal injury and a heightened risk of scar formation. In contrast to millisecond 1064-nm Nd:YAG lasers, microsecond-pulsed lasers deliver energy within the thermal relaxation time of the epidermis, minimizing heat diffusion to surrounding tissues.

Rosacea is a chronic and recurrent dermatologic condition that poses significant therapeutic challenges. While both 532-nm KTP and 1064-nm Nd:YAG lasers demonstrate efficacy in managing rosacea-associated erythema, no single laser system can address all vascular components due to their distinct limitations in penetration depth and vessel selectivity. We need to explore more treatment options. This study aims to evaluate the efficacy and safety of a 532-nm KTP laser combined with a microsecond 1064-nm ND:YAG laser in treating the erythema of rosacea, in order to provide scientific evidence for clinical application.

Inclusion Criteria:

• Participants aged between 18 and 65 years, without cognitive impairments, and of any gender
• Patients must meet the 2017 rosacea diagnostic criteria updated by the National Rosacea Society Expert Committee
• The severity of rosacea must be scored at least 2 points on the Clinician's Erythema Assessment (CEA) scale.

Exclusion Criteria:

• if they had undergone any treatments that could influence the prognosis of rosacea within the preceding 8 weeks
• if they had taken photosensitizing or phototoxic medications within the same period
• the presence of other facial conditions that might confound the efficacy assessment
• participation in any drug clinical trial as a subject within the last month
• the presence of severe concurrent diseases

De-identified participant data (CEA scores, DLQI, GAIS, adverse events) and the study protocol will be made available to qualified researchers beginning 6 months after primary publication. Proposals must be approved by the corresponding author and institution; data will be shared via secure file transfer with a signed data-use agreement.