TCA CROSS: Targeted Treatment for Narrow Acne Scars
Do narrow, deep acne pits catch the side light, and would you like smoother-looking skin without treating your whole face? TCA CROSS is an option for selected narrow atrophic scars, which are depressions caused by tissue loss. A clinician applies trichloroacetic acid very precisely inside the scar. It may make a pit less noticeable, but cannot promise scar-free skin and is not intended to treat flat dark marks left by spots.
Before booking, find out which scar type you have. Deep pinholes, broad wave-like depressions and flat red marks can coexist on one cheek and need quite different approaches. Distinguishing them prevents unnecessary crusting and pigment changes in areas unlikely to benefit.
Which scars are realistic targets?
CROSS means chemical reconstruction of skin scars. A clinician applies a tiny quantity of high-concentration acid only to the surface and sides of a selected depression. This creates a controlled injury; as it heals, the scar's collagen structure may change. This is not a conventional full-cheek peel. Do not attempt it at home: acid on healthy skin, eyes or mucosa can cause lasting injury.
| What you see | Possible explanation | Is CROSS suitable? |
|---|---|---|
| A narrow, deep pinhole with steep sides | Ice-pick scar | A main target, depending on depth and location |
| A small depression with defined walls | Some boxcar scars | Spot treatment may help; broader or deeper ones may need another method |
| A broad wave-like hollow tethered downward | Rolling scar with possible fibrous bands | Evaluate subcision to free the tethered tissue |
| A flat red or brown mark without depression | Post-inflammatory colour change | No; CROSS does not treat the cause of flat colour change |
| A raised thickened area | Hypertrophic or keloid scar | Not a usual CROSS target; separate diagnosis needed |
Mixed scars sometimes call for a staged plan: CROSS for suitable narrow pits and separate assessment of rolling areas for subcision, which releases fibrous tethers, or resurfacing. Treatments need not happen together. Combining them also combines recovery time, irritation and cost, not just possible benefits.
What will change, and what will remain?
CROSS aims to soften the sharp shadow inside some depressions. Even successful treatment rarely removes a scar entirely. The pit may become shallower yet remain visible in side lighting or close up. Enlarged pores, shallow texture changes and surrounding discoloration may not improve in the same way.
Studies are mostly small and heterogeneous, with different acid concentrations, scar types, session counts and photographic assessments. Advertising percentages of improvement are therefore not predictions for your skin. Ask how progress will be judged using matching light and angles and photographs taken after healing, not straight after a scab falls off.
There is no added filler volume, so CROSS will not create an overfilled look. Nevertheless, the treatment can be more conspicuous than the original scars for a while: pale dots, redness and tiny scabs appear. If you worry about colleagues noticing, think about that visible recovery week as well as the eventual scar depth.
What happens during treatment, and does it hurt?
During consultation the clinician looks at the scars from different angles, checks active acne and pigment tendency, and reviews treatments and medicines. After cleansing, concentrated acid is applied in tiny amounts to selected pits. A pale area called frosting may appear where the acid affects skin proteins. It is an expected reaction, not instant smoothing.
You may feel brief stinging or burning. The intensity varies with the number and position of spots and your sensitivity. Anaesthesia is discussed individually and is not always needed. Ask which product will be used, how adjacent skin is protected, and what happens if acid spreads. Eye, lip and nostril-mucosa protection is especially important.
Treating just a few scars may be quick, but assessment and preparation matter just as much as applying the acid. This high-concentration method belongs in professional care, not a home routine. Videos of people using a cotton bud are not safe instructions.
How visible will recovery be in everyday life?
Healing happens in separate dots, not one broad patch. DermNet describes frosting for hours, redness and tenderness over roughly the first one or two days, then scabs that often separate during the following week. These are broad guides, not your personal calendar. Many small scabs together can be quite visible despite the word 'spot treatment'.
| Stage | What may be visible | Planning ordinary activities |
|---|---|---|
| Treatment day | White dots, local stinging, redness | Avoid major photo sessions; ask about cleansing and care |
| Next 1–3 days | Red dots and forming darker scabs | Work may be possible, but scabs show up close; follow makeup restrictions |
| About days 3–7 and beyond | Scabs detach gradually; skin underneath may remain pink | Do not pick scabs for an event: this increases infection and marking risk |
| Weeks to months after healing | Colour slowly settles; contour is assessed later | Compare healed photographs rather than inspecting daily under magnification |
Makeup is not automatically safe at every stage. Ask when the surface has closed and which products are permitted. Foundation over a crust may make its outline more apparent. Leave more time than the expected scab phase before photography, an important meeting, a celebration or a sunny holiday.
Ask about sport, hot baths, saunas, pools and sun according to how the skin is healing. Avoid excess heat, friction, picking and contamination while wounds remain open. Do not restart acids, retinoids or scrubs until healing and clinical permission. Sun protection after healing helps limit pigment change.
How many sessions, and when do results appear?
CROSS is often a course because skin must heal before another controlled injury. DermNet describes several sessions spread over months, not a universal number. Spacing depends on healing, the protocol and pigment risk. Persistent discoloration after a session may lead to a revised plan or stopping altogether.
Assess scar contour over months, not the day a scab detaches: tissue remodelling takes time. An improved old scar does not necessarily return on a fixed schedule, but new active acne can leave new ones. Managing ongoing acne helps protect the overall outcome and does not replace treating existing scars.
Decide on another session from skin response and comparable photographs, not promises to 'finish off' the final depth. Repeated aggressive injury raises the risk of burning adjacent skin, further scars and persistent pigment change. A modest improvement can be a sensible endpoint.
When should you postpone or choose something else?
A separate assessment is needed for inflamed acne, infection, open wounds, marked irritation, keloid tendency, poor healing, frequent herpes outbreaks or reactions to skin products. Darker skin phototypes can face more post-inflammatory hyperpigmentation (dark marks after injury). This calls for discussion of preparation and alternatives, not an automatic ban.
Tell the clinician about current or recent isotretinoin, other systemic medicines, topical retinoids, previous peels or lasers and home acid treatments. Some CROSS protocols advise a long delay after isotretinoin, but evidence and recommendations differ by procedure; the choice needs individual assessment. Never stop prescribed treatment yourself. In pregnancy or while breastfeeding, the limited evidence for an elective high-concentration procedure generally favours postponing and discussing it with your treating clinician.
Never treat an unexplained or changing skin lesion as a 'scar' without diagnosis. A dermatologist should examine it first. If you often develop long-lasting dark marks, have a near-term event, or cannot accommodate weeks of uneven skin colour, declining CROSS for now is entirely reasonable.
Which reactions are expected, and which need help?
Temporary stinging, redness and crusting are expected. Brown or pale post-inflammatory marks, prolonged redness or no improvement can occur. More serious problems include a new or larger scar, merged adjacent pits, infection and chemical injury to healthy skin; pale patches can sometimes persist. Risk varies with scar dimensions, dosage, application technique, phototype and aftercare.
Seek prompt clinical help for pain that grows, spreading redness, increasing warmth, pus, fever or an unexpectedly large wound. If acid enters an eye, immediately rinse it with plenty of clean, cool or lukewarm running water for at least 20 minutes, do not rub it, and arrange emergency medical care at the same time. Do not delay rinsing while waiting for help. Severe eye pain or any change in vision also requires immediate care, not a scheduled check. Arrange a clear contact and complication plan in advance.
What should you compare with CROSS?
For deep narrow pits, compare CROSS with targeted procedures such as punch excision for selected scars. Broad tethered rolling scars may suit assessment for subcision; numerous shallower scars may lead to discussion of fractional lasers or microneedling, with their own risks and downtime. A TCA peel combined with Jessner's solution acts over an area of skin and is not another name for CROSS. (Read the related guide)
The most intensive plan is not obligatory. Sometimes controlling acne and choosing gentle care first is enough. For before-and-after photographs, compare scar type, lighting and time since the last treatment. A red early photograph beside a late photograph in different light cannot reliably show contour improvement.
Questions to ask at consultation
- Which of my scars are ice-pick, boxcar or rolling; which ones would you leave untreated with acid?
- What is a realistic goal: reduced depth, shadow or number of obvious pits; what will stay?
- Is my pigmentation or wound-healing risk higher, and should acne treatment or skincare change first?
- How will you protect healthy skin and mucosa, and respond to a burn or complication?
- When can I wash, use makeup, exercise or spend time outside, and whom should I send concerning photos to?
- What findings would make us stop the course rather than intensify it?
A good consultation can end with 'not now'. This spot technique makes sense only when you and the clinician agree which pits are eligible, what improvement may be realistic and whether the interim appearance is acceptable to you.
Other questions
Can CROSS be performed on just one scar?
Yes, an individual selected scar can be treated, but its shape must be suitable and the possibility of a surrounding colour difference assessed first.
What if the scars are on the nose?
Precautions vary with location. The nostrils and adjacent mucosa make self-treatment particularly hazardous; a clinician needs to assess each nose scar in person.
Can I remove a scab to apply concealer sooner?
No. Pulling off a scab injures healing skin and may increase pigmentation or scarring. A clinician should advise when makeup may safely return.
Sources
- DermNet — TCA CROSS
- DermNet — Acne scarring
- Bhardwaj, Khunger — TCA CROSS for ice-pick scars
- Stratman, He — TCA CROSS techniques, outcomes and complications (2026)
- American Academy of Dermatology — chemical peel preparation
- ASDS — consensus on isotretinoin and skin procedures (2017)
- Mayo Clinic — first aid for a chemical splash in the eye
