TCA for Atrophic Scars

01What is TCA CROSS intended to do?

The aim is to make a suitable depressed scar less noticeable as it heals and remodels. It does not erase the scar or recreate skin that has never been injured.

Improvement is gradual and variable. A scar may become shallower without disappearing. Some scars respond modestly or not at all. A series may be considered, but another treatment should never be automatic: the skin must heal and the response must be reviewed first.

A treated scar can become wider, more noticeable or more atrophic. That belongs in the decision before treatment, not in the small print afterwards.

02Which scars may be suitable?

TCA CROSS may be considered when:

• the scar is genuinely atrophic rather than simply darker or red;
• its shape and depth make focal treatment proportionate;
• active acne is controlled well enough that new scars are not continuing to form;
• the skin barrier is settled;
• pigment and scar-healing risks are acceptable;
• the patient can follow the preparation, recovery and UVA/UVB protection plan; and
• the likely improvement is worth the recovery and risk.

Published evidence mainly concerns atrophic acne scars. Other scar causes are assessed separately and are not automatically included.

03When another route may fit better

TCA CROSS is not a universal acne-scar treatment.

• Rolling or tethered scars may need a treatment that addresses the attachment beneath the scar.
• Broad or shallow boxcar scars may suit another resurfacing or combination approach.
• General surface texture may need a treatment across a wider area.
• Active inflammatory acne should usually be controlled before scar correction becomes the priority.
• Brown or red marks without a change in skin structure are not atrophic scars.
• Severe or diagnostically uncertain scarring may require a specialist dermatology route.

Alternatives may include no treatment, camouflage, microneedling, subcision, laser treatment, punch techniques, selected injectable support or a staged combination. Suitability decides the option; the menu does not.

04The evidence, honestly

One small clinical study reported improvement in selected atrophic scars, with better outcomes in patients whose scars were predominantly boxcar and more severe.^[4] It does not establish what one individual should expect.

NICE considered chemical peels within its acne-scarring evidence, but its treatment recommendation names glycolic acid rather than TCA CROSS, and it called for more research on chemical peels for persistent acne scarring.^[1]

A Cochrane review assessed acne-scar treatments broadly and found the comparative evidence too uncertain to identify one clearly superior option; that was not a TCA-CROSS-specific verdict.^[2]

That does not mean TCA CROSS cannot help. It means I will not borrow a percentage from a small study and present it as your expected result.

05What happens after assessment?

1. Scar assessment. I distinguish ice-pick, boxcar, rolling and tethered scars, active acne and pigmentary marks.
2. Suitability decision. I review skin tone, previous pigmentation, healing, medication, skincare, cold-sore history, earlier procedures and realistic recovery.
3. Plan and consent. You receive the intended treatment area, expected limits, alternatives, material risks, aftercare and contact route.
4. Focal treatment. Only the selected individual scars are treated. This page deliberately gives no concentration or application instructions.
5. Early healing. Small treated sites recover under written aftercare and planned photograph check-ins.
6. Review. The next decision is made after adequate healing and assessment of response, not from a prepaid timetable.

06What recovery may look like

The exact sequence depends on the confirmed protocol and individual healing.

A short period of stinging, warmth, tenderness, local redness or swelling may occur. Small dark crusts commonly form at the treated points over the following days. They should be allowed to separate naturally, usually during the following week, although healing can take longer.

The new skin may initially look pink, red, darker or lighter than the surrounding skin. The scars can look temporarily more obvious while crusting and colour change are present. That is too early to judge the result.

Persistent redness, post-inflammatory hyperpigmentation, lighter pigment and delayed healing can occur. Final change is assessed after the skin has settled, not when the last crust comes away.

07Pigment risk changes the plan

Any skin tone can develop post-inflammatory hyperpigmentation, with a greater predisposition in darker skin tones. After TCA CROSS specifically, PIH can persist beyond early healing, but one small study did not show that skin type predicted outcomes or adverse effects.^[4][6]

I also consider previous PIH, melasma, active inflammation, recent tanning or sunburn, medication, earlier treatment reactions and whether reliable photoprotection is realistic.

Broad-spectrum UVA and UVB protection is part of preparation and recovery. It cannot guarantee that pigmentation will not occur.

Do not pick, pull or scrub attached healing skin. Let it separate naturally; if something worries you, use the contact route provided rather than trying to fix it yourself.

08Aftercare does not end at the clinic door

Planned early-healing photographs help me follow the treated sites and are included in the TCA service. Your written aftercare states when to send them, where they should be sent and what to do if something is urgent. This is planned clinical follow-up, not a promise of 24-hour instant replies.

Possible effects and complications

Possible effects and complications include:

• stinging, warmth or tenderness;
• local redness or swelling;
• small dark crusts at the treated points;
• temporary colour change — pink, red, darker or lighter skin;
• persistent redness;
• post-inflammatory hyperpigmentation or lighter pigment;
• delayed healing;
• a treated scar becoming wider, more noticeable or more atrophic; and
• limited or no improvement.

Frequency is protocol-specific and cannot be given as a reliable individual probability.

When urgent help should not wait

For difficulty breathing, sudden swelling of the lips, mouth, tongue or throat, collapse, severe eye pain or a sudden change in sight, call 999 or go to A&E. Do not wait for a clinic reply.

If a problem is urgent but not life-threatening and the clinic is unavailable, contact NHS 111.

Otherwise contact the clinic promptly if pain increases rather than settles; redness, heat or swelling spreads; blistering, persistent weeping or discharge develops; a cold sore appears; you feel unwell; a treated point extends unexpectedly beyond the scar; healing appears delayed; or pigment change concerns you.

Questions, answered

09References

1. National Institute for Health and Care Excellence. Acne vulgaris: management — evidence review for management of acne vulgaris-associated scarring (NG198, evidence review M). 2021. NICE evidence. Accessed 4 August 2026.
2. Abdel Hay R, Shalaby K, Zaher H, et al. Interventions for acne scars. Cochrane Database of Systematic Reviews. 2016;(4):CD011946. doi:10.1002/14651858.CD011946.pub2. Accessed 4 August 2026.
3. Veenstra JJ, Fakhoury JW, Ozog D. Worsening of acne scars from trichloroacetic acid CROSS delivered via micropipette: a case report. Journal of Clinical and Aesthetic Dermatology. 2021;14(4):41–42. PMCID: PMC8142827. Accessed 4 August 2026.
4. Agarwal N, Gupta LK, Khare AK, et al. Therapeutic response of 70% trichloroacetic acid CROSS in atrophic acne scars. Dermatologic Surgery. 2015;41(5):597–604. doi:10.1097/DSS.0000000000000355. Accessed 4 August 2026.
5. Weber MB, Machado RB, Hoefel IR, et al. Complication of CROSS-technique on boxcar acne scars: atrophy. Dermatologic Surgery. 2011;37(1):93–95. doi:10.1111/j.1524-4725.2010.01820.x. Accessed 4 August 2026.
6. Mar K, Khalid B, Maazi M, et al. Treatment of post-inflammatory hyperpigmentation in skin of colour: a systematic review. Journal of Cutaneous Medicine and Surgery. 2024;28(5):473–480. doi:10.1177/12034754241265716. Accessed 4 August 2026.