TCA CROSS is the chemical reconstruction of skin scars (CROSS) using trichloroacetic acid (TCA). It is most often used as an outpatient clinic procedure to treat atrophic acne scars. It's inexpensive, safe and efficient, but is not always effective. Acne is a common inflammatory skin condition and may result in atrophic, hypertrophic or keloid scars. Acne scars can cause significant psychological distress and social impact. The TCA CROSS procedure involves depositing small amounts of TCA at high concentration (70–100%) onto the surface of the atrophic scar. This causes a local inflammatory reaction leading to the formation of new collagen fibres. The aim is to improve the appearance of the scar by increasing collagen reflectance and reducing shadows cast over scar depressions. Complete resolution is unlikely to be achieved with this treatment method alone.