People with boxcar acne scars should pick treatment by recovery time and pigment risk, not by the winning half-face score. The 2026 split-face trials show overall scar improvement, but they do not prove lasting, boxcar-only, pigment-free benefit. Boxcar scars are wide depressed scars with sharp vertical walls. A split-face trial treats one side of the face with the test treatment and the other side with a comparison, so each person serves as their own control.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What the 2026 split-face trials tested
- What recovery and pigment safety looked like
- Why boxcar scars need a separate read
- How to avoid overreading the headline
What the 2026 split-face trials tested
One 2026 trial randomized 24 Asian adults with moderate-to-severe atrophic scars to fractional microneedle radiofrequency with transdermal poly-L-lactic acid, according to Springer / Dermatology and Therapy in the PLLA-microneedle trial report. The study enrolled Fitzpatrick skin types III-V. It measured overall atrophic scars, not boxcar scars alone.
A separate 10-week 2026 trial randomized 14 patients with bilateral atrophic scars to intradermal stromal vascular fraction versus saline, according to Springer / Dermatology and Therapy in the stromal vascular fraction trial report. Scar counts and ECCA and Scar Global Assessment scores fell more with active treatment. Again, results covered atrophic scars as a group.
What recovery and pigment safety looked like
In the 24-person PLLA-microneedle trial, side effects were transient erythema, acneiform flares, and mild hyperpigmentation in 2 of 24 participants. That 8.3% pigment rate resolved within one month, with no infections or serious events.
A 2026 meta-analysis of 8 randomized trials with 249 patients found fractional CO2 laser gave marginally greater improvement and satisfaction than microneedling radiofrequency, but with significantly higher pain, hyperpigmentation risk, and longer redness, according to Wiley / Journal of Cosmetic Dermatology in the CO2 versus radiofrequency meta-analysis. An earlier single-treatment split-face trial reached the same trade-off: both methods improved scars, while microneedle radiofrequency gave faster recovery and fewer pigment events.
Why boxcar scars need a separate read
Middle Eastern fractional-CO2 data report boxcar and rolling scars respond better than ice-pick scars, according to Dermatology Times in the Middle Eastern resurfacing summary. Ice-pick scars often need adjunct techniques. That pattern matters because a trial average can hide uneven response by scar type.
The 2026 split-face trials were small, with 14 and 24 patients, short follow-up, no stratified boxcar-only efficacy, and half-face treatment that does not replicate full-face healing. Small samples make pigment rates unstable. Short follow-up misses late darkening, recurrence, and maintenance needs.
How to avoid overreading the headline
Bring photos in the same lighting, a list of prior peels, lasers, retinoids, and pigment history, and your work or school calendar. Ask what full-face care, sun protection, and follow-up would add beyond the trial protocol.
- Ask whether results were reported for boxcar scars separately, or only for all atrophic scars combined.
- Ask about downtime, pain, redness duration, and pigment risk for your skin tone.
- Separate true indented scars from brown or red post-inflammatory marks.
- Protect marks from sun and control acne triggers, since marks and dents need different plans.
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