The 2026 split-face acne scar trial found equal scar improvement on both laser sides with no lasting pigment damage, and faster early healing on the picosecond side. A split-face trial treats one side of the face with one method and the other side with another method for direct comparison. Boxcar scars are angular, wide depressions with sharp vertical edges resembling chickenpox scars. This briefing explains recovery, pigment safety, and practical care for people with that scar type.
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 laser trial compared
- Which side recovered faster
- What this means for boxcar scars
- Pigment safety, skin tone, and practical steps
What the 2026 laser trial compared
Qi et al. ran a 20-week prospective randomized split-face trial for atrophic acne scars. One side received 755-nm picosecond laser with diffractive lens array and the other side received 1565-nm nonablative fractional laser.
According to Springer Nature, the report appeared as Lasers in Medical Science 41:210 on 2 Sept 2026 in the journal report. Both laser sides improved without a statistically significant efficacy difference. The authors reported no post-inflammatory hyperpigmentation or other permanent adverse events. That result matters because staining is a central worry for scar treatment.
Which side recovered faster
The picosecond side showed shorter redness and swelling than the 1565-nm fractional side. No crusting was reported on the picosecond side. That pattern points to faster early recovery in that protocol.
Shorter redness means less visible downtime during the first days. Less swelling can make work, school, and social plans easier. According to the SkinWorks Medical summary of the comparison, the picosecond protocol healed earlier in the safety summary.
What this means for boxcar scars
Prior split-face microneedling work found boxcar and rolling scars respond better than deep ice-pick scars. Sharp vertical edges still need energy to reach the dermis, but wide shallow bases are easier to remodel. Deep narrow ice-pick scars remain harder to lift.
A person with mainly boxcar marks fits the more responsive group. A person with mixed scars may see uneven change across scar shapes. Treatment plans often target wide depressions first and reserve spot methods for deep pits.
Pigment safety, skin tone, and practical steps
Kupwiwat et al. ran a randomized double-blind split-face trial of fractional microneedle radiofrequency with transdermal poly-L-lactic acid for moderate-to-severe atrophic scars in Fitzpatrick III-V Asian patients. That trial reported only mild transient harms: 4.2 percent mild erythema resolving within 1 month, 4.2 percent acne flare resolving in 5 days, and 8.3 percent mild hyperpigmentation resolving within 1 month, as reported in Dermatology and Therapy Heidelberg in the trial report. Radiofrequency energy is not melanin-absorbed and should lower hyperpigmentation risk versus fractional lasers.
Practical care includes strict sun protection, lower density in darker skin, and treating pigment after texture settles. Those steps reduce downtime and staining. Generalizability remains narrow because 2026 trials used small samples, 10-20 week follow-up, and mainly Fitzpatrick III-V or Asian cohorts. Pigment risk in type VI and long-term scar relapse remain less documented. People with very deep skin tones need an individualized pigment plan.
- Use daily sunscreen and shade during healing weeks
- Ask about lower density settings for medium and darker skin
- Let texture settle before treating residual brown marks
- Report spreading redness, blistering, or dark patches early
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