This is a 3-arm randomised clinical enabling study, with no investigational product. Keloid patients who are scheduled for surgical excision of one or more keloid scars (up to nine) will be recruited to the study. The aim is to investigate how collagen synthesis within keloid scars is affected by the current approved steroid treatment for keloids, triamcinolone acetonide (TAC). The primary endpoint will be fractional collagen synthesis in keloids which have received intra-lesional injections of TAC, placebo or no treatment prior to their removal. Fractional collagen synthesis will be determined using an established isotope/mass spectrometric technique which measures levels of deuterium incorporation into collagen following administration of heavy water to the subject. In addition; keloid tissue samples will be evaluated post surgery to identify further biomarkers of extracellular matrix synthesis and degradation for application in future clinical studies. Subjects will complete a screening visit and will then be randomised to receive three intra-lesional injections of TAC or placebo, or no treatment, at an interval of 2-3 weeks. Subjects will be randomised to different treatment sequences depending on the number of keloids they have scheduled for surgery, in such a way that subjects with multiple keloids will receive different arms of study treatment in their different keloids. Planned surgery for removal of their keloid(s) will be performed at week 6-8. All subjects will receive daily heavy water (Deuterium oxide) administration (twice daily or thrice daily as directed), with the first dose being taken at the Week 2 clinic visit and the final dose being taken on the day prior to surgery. A follow-up visit will be conducted at 1-4 weeks post-surgery.