Scarring After Cosmetic Surgery: What Shapes a Scar and What the Evidence Shows

The scar is the permanent part of an elective procedure. Swelling and bruising clear within weeks, but the incision line keeps changing for a year or more, and how it matures decides whether it settles into a fine pale line or stays raised, wide, or dark. This article covers how a scar forms, what shapes the outcome, and what the published Hyperbaric Oxygen Therapy (HBOT) evidence does and does not show. Most of that evidence is in problem scars rather than ordinary cosmetic incisions, and it is described below with its limits.

How a scar forms

Wound healing runs in three overlapping phases, described in the StatPearls entry on hypertrophic scars and keloids : an inflammatory phase in the first days, a proliferative phase that starts around day three and lasts for weeks while new tissue and collagen fill the wound, and a remodeling phase over the following months in which that collagen is reorganized and the scar flattens and fades. A hypertrophic scar is one that stays raised but within the original wound and may regress over time. A keloid grows beyond the wound edges and does not regress.

Oxygen sits inside this process. Collagen cannot be assembled without an oxygen-dependent step in its synthesis, and Sen (2009)  reviewed the evidence that collagen production rises with tissue oxygen tension across the physiological range. In 33 post-operative surgical patients, Jonsson et al. (1991)  measured collagen deposition in standardized wounds and found it directly proportional to wound oxygen tension. More collagen is not the same as a better scar, though. The animal work below points to less inflammation, not more collagen, as the route to a flatter scar.

What shapes the outcome

• Tension and location: incisions across lines of skin tension, and on the chest, shoulders, and upper back, are more prone to widening and thickening. Surgeons plan incision placement around this.

• Healing complications: infection, wound separation, and tissue that heals slowly all prolong the inflammatory phase, and StatPearls notes that the inflammatory stage may be the most important in determining the scar.

• Skin type and history: a personal or family history of raised scars raises the risk of another one.

• Aftercare: silicone sheeting or gel, sun protection, and the taping or massage your surgeon prescribes are the standard measures, and they take priority over anything below.

What the HBOT evidence shows

No randomized trial has compared HBOT with no treatment for scar quality after elective cosmetic surgery, and no study has followed cosmetic-surgery scars beyond 12 weeks with a validated scale. What has been published is listed below.

• Friedman et al. (2019) : a retrospective cohort of 356 abdominoplasty patients. Those who completed one to three 90-minute sessions at 2 ATA before surgery had no hypertrophic scars, against 7.3% in the group without HBOT (P = 0.006), alongside no infections and no tissue necrosis. The cohort was more than half post-bariatric, and patients chose their own group.

• Chen et al. (2025) : 33 patients with clean linear surgical wounds, assigned to seven 100-minute sessions at 2.5 ATA starting four weeks after surgery or to silicone sheets. Both groups improved on the POSAS scar scale over 12 weeks. HBOT reduced scar surface area more (44.2% versus 22.3%), and silicone did as well or better on vascularity, pigmentation, thickness, and pliability. There was no untreated group.

• Song et al. (2018) : 240 patients with keloids on the chest or shoulder treated with excision and radiotherapy. Adding two weeks of daily 60-minute sessions at 2 ATA cut recurrence from 14.15% to 5.97%. Groups were assigned by calendar month rather than true randomization. A 2023 meta-analysis by Xie et al.  pooled this with three similar studies and reported an odds ratio of 0.26 for recurrence. Keloid excision and radiotherapy are physician-directed medical treatment, not what OxyRenew provides.

• Ince et al. (2020)  and Ren et al. (2018) : rabbit ear scar models in which daily HBOT from the day after wounding produced thinner scars with fewer fibroblasts and less collagen, which the authors attributed to lower inflammation and higher fibroblast turnover. Animal models only.

A Cochrane review  of HBOT for acute surgical and traumatic wounds found four trials covering 229 participants and concluded that high-quality evidence is lacking. The honest summary is that oxygen is required for collagen formation, that HBOT reduced recurrence and improved scar scores in small studies of problem scars, and that one small study of ordinary incisions found it comparable to silicone on most measures. None of that shows HBOT prevents scarring after cosmetic surgery.

Timing around surgery

For surgical clients, a 6-session package is typically structured as one session before surgery and five as soon as possible after, sometimes the same day if your doctor allows. The studies above ran at different points: before surgery in the abdominoplasty cohort, from day one in the animal models, and from week four in the human incision study. Timing has not been compared in people, and your surgeon decides when you can start.

HBOT in Los Angeles

HBOT is not FDA-cleared for scarring or cosmetic surgery recovery. At OxyRenew in West Hollywood, sessions run in a private 2.0 ATA hard-shell chamber with a Certified Hyperbaric Technician monitoring from start to finish, and you breathe concentrated oxygen through a mask or cannula.

Book your first session online, or contact us to speak directly with a Certified Hyperbaric Technician about timing around your procedure date. You can also read about supplements and healing after surgery and more about HBOT for surgery recovery.