BonBoz Clinic

Acne Treatment

TCA CROSS (Chemical Reconstruction of Skin Scars)

TCA CROSS involves applying high-concentration trichloroacetic acid precisely to the base of each atrophic scar using a toothpick or fine needle, creating a controlled chemical injury that stimulates collagen production from the base of the scar upward. It is ideal for ice pick and deep, narrow boxcar scars, leaving the surrounding healthy skin unaffected. Treatments typically require 3–6 sessions spaced 4–6 weeks apart.

Compiled from BonBoz Clinic clinical documentation — currently in medical review

Mechanism of Action

The acid causes protein coagulation and controlled injury within the deep dermis at the base of the scar. The subsequent wound healing process stimulates neocollagenesis, gradually raising the scar floor. Because the acid is applied strictly inside the scar depression, the surrounding healthy skin remains untouched—unlike full-face chemical peels. This provides a "bottom-up" approach for deep scars that "top-down" modalities like lasers or microneedling cannot reach.

Ideal Candidates & Indications

Ice pick scars—the primary indication; deep, narrow boxcar scars; and enlarged post-acne pores. It is not indicated for broad rolling scars (which require subcision), hypertrophic or keloid scars, nor is it a stand-alone replacement for a comprehensive treatment plan. TCA CROSS is typically one component of a multi-modality regimen, combined with fractional CO2 laser or RF microneedling for other scar types on the same face.

Why Must It Be Performed by a Physician?

The acid concentration used is exceptionally high; any spillage onto healthy skin can cause chemical burns, secondary scarring, or permanent depigmentation. A physician selects the appropriate concentration based on scar depth and skin type, applies a micro-droplet precisely into each scar, and monitors the clinical endpoint of "frosting" before neutralizing or stopping. Performing this procedure at home with online-purchased TCA solutions is a frequent cause of severe scarring and worsening hyperpigmentation.

Treatment Sessions and Expected Results

Typically 3–6 sessions spaced 4–6 weeks apart. Treated points form small scabs that shed within 5–7 days. The scar depth gradually becomes shallower and the scar opening tightens with each session; the degree of improvement depends on initial depth and individual healing response. Darker skin phototypes carry a higher risk of temporary post-inflammatory hyperpigmentation (PIH) at the treated spots—strict sun protection is essential.

At BonBoz Clinic

A dermatologist examines your skin, maps out each individual ice pick and deep boxcar scar, selects the precise acid concentration, manually performs focal application point by point, and integrates resurfacing modalities for the remaining scars according to your tailored treatment plan.

Technique variants

1

Low concentration, multiple sessions

Safer for hyperpigmentation-prone skin, requires several visits.

2

High concentration, fewer sessions

Stronger impact per session, requires strict post-treatment care.

3

Combined TCA CROSS

Alternated with subcision or lasers within the same treatment plan.

When should you see a doctor?

  • Wide rolling or boxcar scars — TCA CROSS is best suited for ice pick scars and is not suitable for all scar types.
  • Active inflammatory acne or skin currently peeling from strong topical treatments.
  • High susceptibility to post-inflammatory hyperpigmentation (PIH), or inability to strictly avoid sun exposure post-treatment.
  • Active facial skin infections.

How is it performed?

The skin is cleansed and disinfected. Anesthesia may not be necessary (as it only causes a brief stinging sensation) or a mild topical anesthetic may be applied. The doctor uses a toothpick or fine needle dipped in the selected concentration of TCA to dot the base of each scar until frosting occurs—taking a few seconds per scar, and around 15–30 minutes for several dozen scars. Afterward, a soothing ointment and sunscreen are applied.

Before the procedure

Discontinue topical retinoids for 5–7 days; avoid sun exposure for 1–2 weeks prior; disclose any history of keloids or herpes; control inflammatory acne beforehand; arrive with clean skin.

After the procedure

The treated spots will turn red and form brown scabs within 5–7 days — do not pick at them; cleanse gently, apply prescribed recovery cream, and strictly use SPF 50 sunscreen for 4 weeks; avoid exfoliating the treated areas for 2 weeks. Follow up in 4–6 weeks for the next session.

Possible risks — your doctor explains them before treatment

  • Temporary hyperpigmentation at treated spots, especially in darker skin types or without sun protection
  • Mild burning and erythema for a few hours post-treatment
  • Scar widening or localized hypopigmentation if acid spills onto healthy skin or if the concentration is inappropriate
  • Variable response across individual scars — multiple sessions required
  • Herpes reactivation in patients with a history of the virus

Who should NOT have this?

  • Broad rolling scars (require subcision, not spot treatment)
  • Keloids or a history of keloid-prone skin
  • Active inflammatory acne, dermatitis, or active herpes infection
  • Very dark skin tones without prior assessment of hyperpigmentation risk
  • Currently pregnant (postpone treatment)
  • Individuals purchasing TCA for DIY at-home application — extremely high risk of chemical burns and new scarring

How BonBoz uses it

Subcision

Subcision utilizes a specialized needle inserted beneath the skin's surface to sever the fibrous bands pulling the scar base downward. This is a core step for rolling scars, often combined with laser therapy or microneedling to smooth the skin surface afterward.

Learn about this method →

Microneedling

Microneedling creates thousands of micro-injuries to stimulate natural collagen production—minimally invasive with a fast recovery, suitable for shallow pitted scars and uneven skin texture. For deep scars, microneedling alone is often insufficient and requires a combination approach.

Learn about this method →

Fractional CO2 Laser for Pitted Scars

Fractional CO2 laser creates thousands of controlled microscopic treatment zones to trigger self-collagen regeneration and elevate the base of pitted scars. Effective for boxcar scars and shallow-to-moderate rolling scars; requires multiple sessions and strict sun protection.

Learn about this method →

Acne Treatment

Services page: A specialist physician conducts an examination, recommends a suitable treatment plan, and discloses costs upfront before you decide.

Learn about this method →

Want a cost range for your own case?

Estimate the cost →

Cost guidance

The cost depends on the number of scar spots requiring treatment, the number of sessions in the treatment plan, and whether it is combined with other procedures.

The final price follows the doctor’s recommendation after an in-person exam. A confirmed quote has no hidden extras.

Inside the BonBoz clinic

Bác sỹ BonBoz Clinic soi da cho khách hàng trước điều trị
Bác sỹ BonBoz Clinic thực hiện điều trị laser cho khách hàng
Hệ thống thiết bị laser và ánh sáng tại BonBoz Clinic

Book a consultation with a doctor

Choose a date, time slot and doctor — the clinic calls to confirm within 5 minutes during opening hours. Free consultation, no commitment.

Preferred date · Preferred time · Doctor

The clinic will call to confirm within 5 minutes during opening hours (08:00–20:00, daily). This is not yet a confirmed slot.

You do not have to describe your health condition here — you can discuss it directly with the doctor at your visit.

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Frequently asked questions

Is TCA Cross painful?

You will feel a brief stinging sensation for a few seconds at each spot, which subsides quickly; mild topical anesthesia can be applied. Most clients tolerate it well without numbing cream.

How long does it take for the scabs to fall off?

5–7 days; afterward, the treated spots will remain pink for a few weeks before blending with your natural skin tone. Do not pick at the scabs to prevent post-inflammatory hyperpigmentation.

How many sessions are needed?

Typically 3–6 sessions, spaced 4–6 weeks apart. The scars will become progressively shallower with each session; your doctor will evaluate your skin before the next treatment.

Can it cause new scars?

No, provided that the correct concentration and precise technique are used. Spillover onto healthy skin or an incorrect concentration can cause damage — which is why it must be performed by a doctor.

Can darker skin tones undergo this treatment?

Yes, but there is a higher risk of temporary hyperpigmentation; the doctor will use an appropriate concentration, and strict sun protection is mandatory.

Can TCA Cross replace laser treatments?

No, it cannot — these two modalities target different types of scars and are often combined on the same face.

Can it be done on the same day as laser treatment?

They are usually separated into different sessions or TCA is applied first, followed by laser treatment once healed; your doctor will determine the sequence based on your skin condition.

Can I buy TCA to apply at home?

No. High concentrations can cause chemical burns, new scars, and depigmentation if spread onto healthy skin — many patients come to our clinic seeking treatment for these exact complications.

How soon will I see results?

Scar openings are visibly reduced after 2–3 sessions; collagen continues to remodel for weeks following each treatment.

Who performs the procedure at BonBoz?

Our Dermatology Specialists directly perform the precise application at every single spot — this is never delegated to technicians.

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