The 2026 split-face trial studied 27 adults with atrophic acne scars and Fitzpatrick skin types III–IV. Boxcar scars, broad sharp-edged pits often 1.5–4 mm wide, were included without a separate result, while types I–II and V–VI were not studied.
In this cohort both cheeks improved to a similar degree. Investigators saw no lasting color change or permanent harm during follow-up. The picosecond side settled faster with less redness and swelling.
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 each cheek received
- How healing and color risk compared
- Who was not studied
- What boxcar scars mean for these results
What each cheek received
According to Springer Nature Lasers in Medical Science, investigators ran a 20-week prospective randomized split-face trial in 27 patients with atrophic scars the published trial report. One cheek received 755-nm picosecond laser with diffractive lens array. The other cheek received 1565-nm nonablative fractional laser.
Patients received three sessions spaced 4 weeks apart. Each person served as their own control. That design highlights cheek-to-cheek differences in healing.
How healing and color risk compared
The SkinWorksMed expert review summarizes the split-face results as comparable scar improvement with no significant difference between sides the expert review of the split-face results. That comparison rests on only 27 patients. The same review notes faster settling on the picosecond side with shorter redness and swelling and no crusting.
The trial safety data in Springer Nature Lasers in Medical Science recorded no post-inflammatory hyperpigmentation or permanent adverse events on either side during follow-up the trial safety findings. That expert review describes 1565-nm treatment as typically causing transient redness, warmth, swelling, and short downtime. Short-term pigment safety therefore looked reassuring for types III–IV in this setting.
Who was not studied
The trial report limited enrollment to Fitzpatrick types III–IV. People with very fair type I–II skin or dark type V–VI skin were not represented.
That gap matters most for pigment risk. People with any of these histories were also excluded: If one of these applies, the trial offers no direct safety data. Active acne was also outside the studied scar population.
- keloid history or lidocaine allergy
- photosensitivity, photosensitizing drugs in the prior 6 months, or phototherapy in the prior 6 months
- bleeding disorder or anticoagulant use
- severe systemic disease, immunosuppressant use, or infectious skin disease
- pregnancy
What boxcar scars mean for these results
The U.S. National Library of Medicine / PMC description defines boxcar scars as broad, sharply demarcated atrophic lesions commonly 1.5–4 mm across the atrophic-scar description. People with boxcar scars fall inside the trial atrophic-scar population. They did not receive a separate boxcar-only outcome.
The limits are small size, 20-week follow-up, and narrow eligibility. The findings do not establish pigment or keloid risk for darker skin, pregnancy, active acne, or longer-term recurrence. Those readers need individualized counseling and sun protection. Bring your scar history, medication list, and sun habits to that visit.
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