TCA CROSS / Subcision for Acne Scars

Acne scars can persist long after breakouts have cleared, affecting not only the texture of your skin but also how light reflects across your face. These scars often sit deeper within the skin and may not respond well to topical treatments or standard lasers alone.

These scars develop when inflammation damages the deeper layers of the skin during healing. Instead of regenerating smoothly, the skin heals unevenly, leaving indentations, pits or depressed areas. Common scar types include icepick scars, boxcar scars and rolling scars, each with different structural characteristics. Because each scar varies in depth, shape and pattern, identifying the type of scar is essential in choosing the most effective treatment.

At Dermatology Collective, we use targeted techniques such as TCA CROSS (Trichloroacetic Acid Chemical Reconstruction of Skin Scars) and subcision to address scars at their structural source. Treatment plans are personalised to your skin type, scar pattern and overall skin health to restore a smoother texture and a more even appearance gradually.

What is TCA CROSS?

TCA CROSS is a targeted chemical procedure designed to treat deep, narrow acne scars, particularly icepick scars and deep boxcar scars that are often resistant to topical treatments or conventional laser resurfacing. During the treatment, a small amount of high-strength trichloroacetic acid (TCA) is carefully applied directly into the base of each scar. This stimulates the skin’s natural collagen production, gradually lifting and smoothing the depressed areas without affecting surrounding healthy skin.

How does TCA CROSS work?

The treatment works by harnessing the skin’s natural healing and collagen remodelling processes.

• Controlled chemical injury – applying a high-strength trichloroacetic acid solution directly to the base of narrow scars causes a precise, localised injury. This is confined to the scar tissue, sparing surrounding healthy skin.
• Stimulation of collagen production – the controlled injury triggers the body’s wound-healing response, activating fibroblasts to produce new collagen within the scar.
• Gradual scar lifting – as collagen accumulates, the depressed scar gradually fills in from beneath the skin surface.
• Selective targeting – because TCA is applied only to the scar base, the surrounding epidermis remains intact, minimising the risk of unwanted pigment changes or surface damage.

TCA CROSS is particularly effective for icepick scars and deep, narrow scars that are resistant to surface-level treatments.

What is Subcision?

Subcision is a minimally invasive treatment that targets depressed or tethered scars, particularly rolling scars. 

These scars form when fibrous bands develop beneath the skin and pull the surface downward. During subcision, a fine needle is inserted under the scar to release these fibrous attachments. This allows the skin surface to lift and stimulates natural collagen formation beneath the scar. 

Over time, this process helps improve skin texture, scar depth and overall smoothness. Subcision is often combined with treatments such as TCA CROSS or fractional laser resurfacing to enhance overall results.

How does Subcision work?

The treatment addresses scars that are mechanically tethered to deeper tissue, which creates a rolling or depressed appearance.

• Release of fibrous bands – depressed scars often form because fibrous bands pull the skin downward. Subcision mechanically releases these bands.
• Controlled micro-injury – the needle movement creates controlled micro-trauma beneath the skin. 
• Collagen remodelling – the healing process recruits fibroblasts to produce more collagen and connective tissue.
• Structural improvement – by addressing the underlying architecture of the scar rather than just the surface, subcision provides long-lasting improvement in texture and skin smoothness.

What can TCA CROSS / Subcision treat?

Both treatments address different structural causes of acne scars, making them suitable for specific scar types. A thorough assessment is required to determine which treatment is most appropriate.

TCA CROSS

Most suitable for:

• Icepick scars
• Deep boxcar scars
• Localised, narrow, depressed scars
• Scars that have not responded to lasers or topical therapies

Subcision

Often used for:

• Rolling scars
• Tethered boxcar scars
• Wide or depressed scars 
• Uneven skin texture caused by fibrous bands beneath the skin

What to expect during TCA CROSS / Subcision sessions

The treatments are precise and minimally invasive procedures, which typically involve:

Before the session

Our doctor begins with a thorough assessment of your scars, including their type, depth and distribution. This evaluation helps determine the most suitable treatment approach. During the consultation, our doctor will also explain the procedure, potential side effects, expected recovery and realistic treatment outcomes. 

During the session

The treated area is first cleansed and a numbing agent may be applied to improve comfort. 

For TCA CROSS, a small amount of high-strength trichloroacetic acid is carefully placed at the base of individual scars to stimulate collagen production. 

For subcision, a fine needle is inserted beneath the skin to release fibrous bands pulling the scar downward. 

Both procedures are highly targeted and designed to minimise damage to surrounding healthy skin. Sessions typically last between 30 and 60 minutes, depending on the number and severity of scars.

After the session

It is normal to experience mild redness, swelling or small scabs at the treated sites. These are part of the skin’s natural healing response. Some patients may notice temporary crusting or darkening of the treated scars, which usually resolves over the first few days.

Aftercare and recovery

Proper care after treatment is essential to maximise results and minimise complications. Key aftercare steps include:

• Keeping the treated area clean and dry
• Avoid picking, scratching or rubbing scabs or crusts
• Using only prescribed or recommended skincare products
• Applying broad-spectrum sun protection consistently
• Pausing active skincare, such as exfoliants or retinoids, until advised

Downtime varies depending on the treatment intensity and individual healing response. Most patients can resume normal daily activities immediately, while full healing and visible improvement develop gradually over several weeks.

How many sessions will I need?

What results can I expect?

Results from TCA CROSS and subcision develop gradually as the skin heals and collagen remodels over time. Unlike topical treatments or standard lasers, these procedures work beneath the surface to address the structural causes of scarring.

• Gradual improvement – treated scars may appear slightly red or raised at first, but over several weeks, collagen formation smooths the skin and softens depressions.
• Enhanced skin texture – rolling or deep scars become less noticeable and overall skin surface appears more even.
• Long-term benefits – with proper aftercare, improvements are typically durable, as the skin’s own regenerative processes rebuild scarred areas.
• Complementary effects – combining TCA CROSS and subcision with other treatments, such as laser resurfacing or microneedling, can further enhance tone, texture and overall skin appearance.