This is an observational cohort study which will look at the biomarkers from blood and tissue sample for adult patients with hypertrophic scarring due to burns/trauma incident over 12 months from date of recruitment. The study will assess the kinetics of the response to fractionated carbon dioxide laser therapy in hypertrophic scars.

Research has identified a gap in the knowledge of how fractional ablative carbon dioxide laser works on hypertrophic (thickened) scars. At present there is no accurate measure of how effective the benefit is objectively (medically), subjectively (to the patient) and histologically (on a microscopic level). Recent systematic review has shown an improvement in scars following laser therapy, however it found the quality of the data to be poor, confounded by multiple bias, identifying the lack of evidence to prove the worth and effectiveness of lasers. It concluded the need for more robust studies.

The study plans to observe a group of patients with hypertrophic burn and/or trauma scars (over 1 year old) and see what happens to their scars using the fractionated carbon dioxide laser therapy. Two similar scars will be identified per patient volunteer and will randomly allocate to receive either fractionated carbon dioxide laser therapy or standard care. An independent assessor will be blinded to the intervention and control scar sites.

The trial will aim to identify any biological markers found in participants blood and scar tissue and if they change through the course of and following laser therapy. This will help with understanding the mechanism of how the carbon dioxide laser works on scars.

As part of the evaluation of the impact of laser treatment on patients' quality of life, a patient reported outcome measures (PROMS) validation study will be carried out. PROMs describe how the patient is functioning or feeling without input from clinical staff providing a unique perspective of patients' lived experience of the disease as not all symptoms or impacts are obvious to clinicians. In order for PROMs to be effective in clinical trials and practice, they have to capture information on domains that matter to the patient. These include: scarring, movement and function, scar sensation, psychological distress, body image and confidence, engagement in activities, treatment burden and impact on relationships.

The scars will be assessed in a number of different ways; scar assessment tools/questionnaires, clinical inspection, photography, use of ultrasound, probes with suction to test the elasticity and pliability of the scars and the colour, microscopic evaluation and the identification of biomarkers from blood samples and scar and normal tissue biopsy.

Inclusion Criteria:

• Adult patients aged ≥ 16years
• Patient with hypertrophic scarring as a result of deep dermal or full thickness burns/trauma.
• Trauma or Burn sustained more than 12 months prior to recruitment.
• Treatment area to be ≥25cm2 confluent scarring with a comparable control scar on limb or trunk

General Exclusion Criteria:

• Patients under 16 years of age
• Previous laser therapy treatment to the study site
• The use of recent (within 6 months) or concurrent invasive scar treatments, including intra-lesional pharmaceuticals, micro needling or other laser modalities (e.g. Pulse-dye.)
• Known allergy or contraindication to EMLA™ 5% Cream (Lidocaine 2.5% and Prilocaine 2.5%), Dermol 500TM (Benzalkonium Chloride 0.1%; Chlorhexidine Dihydrochloride 0.1%; Liquid Paraffin 2.5%; Isopropyl Myristate 2.5%) or 50:50 ointment (White Soft Paraffin Liquid Paraffin %w/w 50 50.)
• Patients with Fitzpatrick skin type of 5-6 due to nature of the skin

Laser Treatment Exclusion Criteria

• The presence of acute infection at the proposed treatment site
• Pregnancy or lactation
• Patients with poorly controlled Diabetes mellitus HbA1C >9% or 75mmol/mol within last 3 months)
• Patients experiencing acute exacerbation of Chronic skin diseases e.g. psoriasis or eczema
• Immunosuppression (HIV, drugs with immunosuppressive effect)
• Use of Roaccutane at any time within the last 6 months
• Autoimmune disorders in active stage (for example: 1. Localised; Type 1 Diabetes Mellitus, Addison's, Grave's and Crohn's Disease, 2. Systemic; Rheumatoid Arthritis, Multiple Sclerosis, Lups and Scleroderma).
• Known history of keloid scarring

Adult patient with hypertrophic scarring as a result of deep dermal or full thickness burns/trauma sustained more than 12 months prior to recruitment.