TCA CROSS (that’s “trichloroacetic acid chemical reconstruction of skin scars”) is a well-established procedure for diminishing the appearance of atrophic acne scars. It originated in Korea, which is surprising to exactly no one given the Korean obsession with perfect skin.
Basically, most acne scarring forms sunken areas in the skin due to damage/loss of collagen. These atrophic scars are further classified as “icepick” (narrow/deep), “boxcar” (wide depressions with steep vertical sides), or “rolling” (rolling/undulating appearance of the skin). TCA causes coagulative necrosis of cells and collagen in the upper layers of the skin which causes sloughing of the damaged layers followed by repair/remodeling from the adjacent non-damaged cells, with increased collagen, glycosaminoglycan, and elastin leading to an increase in dermal volume, reducing the appearance of the atrophic scar.
The technique itself is straightforward: apply high-concentration TCA to the base of a scar until it frosts (reflecting epidermal/dermal protein coagulation and indicating that the TCA has penetrated to the desired depth), cover with an occlusive dressing, then let it heal. Avoid the sun and use some sort of anti-hyperpigmentation regimen, usually hydroquinone + tretinoin.
Still, it’s a procedure with non-negligible risks, chiefly related to the use of TCA (which its MSDS helpfully points out is hazardous to skin). So uh, don’t try this at home? (This is my official statement that I am not recommending that anyone else try this, just documenting what I myself did.)
I’m Fitzpatrick IV, which in practical terms means I have a medium skin tone, tan easily/rarely get sunburnt, and am prone to hyperpigmentation. The Skin Cancer Foundation has a fun little quiz about Fitzpatrick types. There are plenty of papers (including the original one describing the CROSS technique) which showed good results in Fitzpatrick IV-V patients without excessive hyperpigmentation, but I still opted to use a lower TCA concentration (50% instead of the typical 65-100%) to decrease the risk of hyperpigmentation.
For an objective measure of scarring severity: my Goodman score pre-treatment is a 10, which isn’t that bad. I have a few hyperpigmented spots, a lot of shallow boxcar scars, and a few icepick scars, but no deep boxcar scars or rolling scars.
Photos were taken at night in my bathroom so the lighting isn’t ideal. I didn’t get a good photo of the icepick scars on my nose, but they’re there (and are actually the reason I looked into TCA CROSS in the first place).
Prior to doing the peel my skincare routine was to double-cleanse at night with an oil cleanser + mild liquid cleanser, followed by 2% salicylic acid wipes (Stridex) and moisturizer. I wasn’t using any particular brand for the cleansers or moisturizers. Retrospectively I might have wanted to use a topical retinoid and/or hydroquinone-containing product as a pre-peel treatment, but I didn’t plan that far ahead (and it wasn’t done in the original paper, which was the first one I read). Whoops. I was at least using sunscreen religiously.
I spot-tested the night before on my left inner elbow (on a scar from donating blood, which tangentially I can no longer do because it tested positive for Hep B surface antigen on an initial screen and the Red Cross sent me a nice letter saying hey, we confirmed that this was a false positive, but you’re still not allowed to donate blood with us ever. On the plus side, I no longer get obnoxious phone calls from them). The patch frosted as expected with minimal stinging/burning pain, followed by disappearance of the frost and mild local erythema. The next day my spot test looked hyperpigmented as expected, so I went ahead and did my entire face.
The procedure itself:
- Wash face and hands with oil-free soap. Put on latex/nitrile/whatever gloves. Clean skin with alcohol wipes. (I meant to do acetone too but apparently instead of 100% acetone I have some weird protein-fortified acetone meant to keep your nails from looking like you used acetone on them so I elected to skip that step.)
- Stretch each scar and apply 50% TCA with wooden toothpick to the base of the scar. (This didn’t burn as much as doing it on my inner elbow did. I had a hand fan nearby because one of the papers I read mentioned using this to alleviate the pain, but I found it entirely unecessary.)
- Monitor for frosting, re-apply in areas that didn’t frost. Some protocols suggest washing to relieve pain/erythema. I didn’t wash my face after this step because TCA is self-neutralizing and I wasn’t experiencing any discomfort.
- Apply topical antibacterial ointment. If I had Vaseline in a tube I would have used that instead since there isn’t really a need for the “antibacterial” part of the ointment, just the occlusive barrier part, but I wasn’t about to use Vaseline from a used tub on my newly-chemically-burned skin.
Post-CROSS so far I’ve been washing my face just with water and applying the ointment after each time I wash my face. The spots darkened over the course of the first night/day.
- Day 0: Treated areas on cheeks went from frosted to hyperpigmented pretty quickly; treated area on nose stayed frosted longer and did not become as darkly hyperpigmented.
- Day 1: Hyperpigmentation of all spots continued to darken over the course of the day. Some scars appeared wider than before, though I’m not sure is that’s because of the hyperpigmentation extending beyond the scar itself due to less-than-precise application or not. My boyfriend says the spots look like freckles (over videochat, anyway) and that they’re kind of cute.
- Day 2: No obvious changes from yesterday. On close inspection there may be some crusting/scabbing starting to happen on my cheeks, but not my nose.
I’m impatient for things to start happening, but TCA is usually repeated 3+ times at 1-3 month intervals and the full results of each treatment take months to become evident. Everything is progressing as expected, which is all I can hope for at this point anyway.