Laser therapy has become a conventional treatment of chronic burns scars for hypertrophy and contracture, with excellent results. Various types of laser can be used, but all rely on selective wavelengths and energy pulsing to selectively heat and ablate superficial tissue, without causing underlying thermal damage beyond the target tissue. Beyond these technical features, effective laser therapy relies on the experience and technique of the laser operator. The synergy of technology and skill allow ablation of hypertrophic scar with necessary precision. Burns laser is being performed under topical local anaesthetic in adult burns services, but what if topical local anaesthetics are affecting scar thickness and interfering with this precision. As topical local anaesthetic is absorbed into the skin it will temporarily accumulate, subtley changing the biomechanical properties of the skin. Previous authors have shown that topical local anaesthetic significant changes the thickness of normal skin, but there is no existing primary research to assess whether the same phenomenon is occurring in chronic burns scars. Due to the greater tissue hardness, and lower visco-elasticity of burns scar than normal skin, will burns scar be temporarily thickened by topical local anaesthesia? As more laser is performed in the outpatient setting in the pursuit of shorter waitlist times, such a question must be answered to ensure the same quality of care. We present the rationale of a randomized controlled trial currently pending ethics approval for assessment of scar thickness pre and post application of topical local anaesthetic prior to outpatient burns laser.