What is post-inflammatory hyperpigmentation?

Post inflammatory hyperpigmentation, often shortened to PIH, is a change in skin tone that can happen after inflammation or injury. It appears as flat dark spots or dark patches rather than a change in skin texture.

Inflammation can stimulate pigment producing cells, called melanocytes, to produce more melanin. That extra pigment can remain in the skin after the original acne inflammation or treatment reaction has settled.

The British Association of Dermatologists' acne guidance explains that acne can leave both hyperpigmented areas, which are darker than a person's usual skin colour, and hypopigmented areas, which are lighter. PIH also has a greater tendency to affect darker skin tones and can be more persistent.

Hyperpigmentation can take several months to fade depending on its depth. This means a pigmentation change should be monitored over time rather than judged only by how it looks immediately after treatment.

What is hypopigmentation?

Hypopigmentation is the opposite of hyperpigmentation. Instead of becoming darker, an area of skin becomes lighter than the surrounding skin.

This can happen if pigment producing cells are damaged or produce less melanin following inflammation, trauma or treatment. In some cases the change improves as the skin heals, but persistent hypopigmentation can be more difficult to correct.

People looking for treatment for hypopigmented acne scars should be cautious about promises of a guaranteed result. The most appropriate treatment depends on the cause, depth and extent of the pigment change, as well as the person's skin type.

What is the difference between pigmentation and acne scarring?

Pigmentation changes colour, while acne scars change the texture or contour of the skin.

Post-inflammatory hyperpigmentation usually appears as flat brown, grey or dark marks. Hypopigmentation appears as lighter areas. By contrast, atrophic acne scars create depressions in the skin and can include ice pick scars, boxcar scars and rolling scars. Raised scar tissue can also develop in some people.

Why can acne treatments cause pigmentation changes?

Acne-scar procedures deliberately affect the skin to encourage repair or remodelling. Laser treatment, laser resurfacing and chemical peels can all trigger inflammation as part of the healing process.

That inflammation can affect melanin production. In some people, the skin responds by producing more pigment, leading to post inflammatory hyperpigmentation. In others, pigment may be reduced, leaving lighter patches.

Harsh treatments or aggressive exfoliation can lead to increased pigmentation. The risk can increase if treatment is too aggressive, the skin barrier is already irritated, active acne is still inflamed, or the procedure is not well matched to the patient's skin type.

Why are darker skin tones more at risk of pigmentation changes?

Darker skin contains more melanin, and inflammation can trigger a more noticeable increase in pigment production. Post inflammatory hyperpigmentation has a greater tendency to affect darker skin tones and can be persistent once it develops.

People with black skin and other darker skin tones can still have acne-scar treatment, but pigmentation risk should be considered carefully.

A practitioner should consider the patient's natural skin tone, previous pigmentation problems, the type of acne scars present and how the skin has reacted to earlier treatments before recommending a procedure.

Can laser treatment for acne scars be used on black skin?

Yes. Laser treatment can be used on darker skin, but not every laser type or treatment setting is suitable for every patient.

People with black or darker skin who are considering laser treatment for acne scars should be assessed individually. This is particularly important when considering laser treatment for acne scars on black skin, as melanin can affect how laser energy is absorbed.

Poorly selected laser treatment or unsuitable settings can increase the risk of burns, post inflammatory hyperpigmentation, hypopigmentation and scarring. Treatment settings should therefore be adapted to the patient's skin, including factors such as energy, treatment density and the number of passes.

Can laser treatment worsen hyperpigmentation?

Yes. Laser treatment can sometimes worsen existing pigmentation or create new dark patches because the energy delivered to the skin causes inflammation.

A laser can also cause burns or prolonged redness if settings are too strong. However, pigment change can occur even when treatment has been carried out appropriately.

The relevant question when considering negligence is whether the practitioner properly assessed suitability, chose appropriate settings, monitored the skin response and stopped or adjusted treatment if there were signs of excessive injury.

Cosmetic Surgery Solicitors also provides information about claims involving laser skin resurfacing injuries and laser treatment negligence.

Can chemical peels cause hyperpigmentation?

Chemical peels can also cause pigmentation changes because they remove or damage controlled layers of skin and trigger a wound healing response.

Peels using ingredients such as glycolic acid may be used to improve skin texture, active acne or dark spots, but the concentration, contact time and depth of the peel should be appropriate for the individual.

Exfoliating acids can slough off pigmented skin cells and improve pigmentation. However, stronger or poorly selected treatments may also irritate the skin and increase the risk of pigmentation changes.

PIH can occur after a chemical peel without negligence, but risk may increase if the peel is too strong, the patient is unsuitable or an excessive reaction is not recognised.

Cosmetic Surgery Solicitors has further guidance on chemical peel injury compensation.

How should skin type be assessed before acne-scar treatment?

A proper initial consultation should consider more than the appearance of the acne scars.

The practitioner should review factors such as:

• Natural skin tone and skin type
• Previous post inflammatory hyperpigmentation or hypopigmentation
• Active acne or ongoing inflammation
• Existing skin conditions
• Recent sun exposure or tanning
• Previous reactions to laser treatment or chemical peels
• The type and depth of the acne scars
• Any medicines or skin care products that may affect healing

Where appropriate, a patch test or more cautious treatment plan may be considered before treating a larger area.

What should patients be told before treatment?

Patients should be given enough information to make an informed decision about whether treatment is right for them.

This should include the expected outcome, likely downtime, realistic limits of improvement and the risk of adverse reactions such as persistent redness, burns, scarring, hyperpigmentation or hypopigmentation where relevant.

The GMC's guidance for doctors offering cosmetic interventions states that clinicians should discuss outcomes, benefits and risks clearly, consider the patient's medical history and give patients enough time and information to make a voluntary decision.

Patients should also be told about reasonable alternatives where they exist.

When could treatment settings indicate negligent care?

Treatment settings may become relevant to a negligence claim where independent medical evidence shows they were inappropriate for the patient's skin type or condition.

Potential concerns can include:

• Excessive laser energy or intensity
• Using an unsuitable laser type
• Too many passes over the same area
• Treating skin that is already inflamed or damaged
• Using an inappropriate chemical peel strength
• Failing to adapt treatment for darker skin tones
• Continuing despite clear signs of excessive redness, burning or skin injury

These factors do not prove negligence on their own. The treatment must be assessed against the standard expected of a reasonably competent practitioner.

What should happen if pigmentation develops after treatment?

If pigmentation develops, the practitioner should assess the skin rather than simply assume the reaction will settle.

They may need to review the treatment plan, stop further sessions, look for burns or infection and consider whether medical or dermatological assessment is needed. Appropriate aftercare should also be explained clearly.

If dark patches are worsening, the skin is blistering, pain is increasing or the area is not healing as expected, further treatment should not continue without proper reassessment.

Seek prompt medical advice for blistering, increasing pain or poor healing. If the skin is painful, hot and swollen, seek an urgent GP appointment or NHS 111 advice rather than waiting for the next cosmetic appointment. 

When is hyperpigmentation more likely to be a recognised complication?

Hyperpigmentation may be a recognised complication where it develops as part of the skin's inflammatory response despite appropriate treatment and aftercare.

Risk can be higher in darker skin tones, after procedures that deliberately disrupt the skin, or where there is significant acne inflammation before treatment. Sun exposure during recovery can also make existing pigmentation more noticeable.

The fact that pigmentation was a recognised risk does not remove the practitioner's duty to assess suitability, explain that risk and respond appropriately if complications develop.

When could hyperpigmentation after acne treatment be negligence?

A pigmentation change may be relevant to a negligence claim where a practitioner failed to meet their duty of care and that failure caused avoidable harm.

Before treatment

Potential failures may include:

• Failing to assess the patient's skin type properly
• Failing to ask about previous pigmentation changes
• Treating active or inflamed acne without proper consideration
• Failing to explain the risk of lasting changes in skin tone
• Failing to discuss realistic outcomes or suitable alternatives

During treatment

Potential failures may include:

• Using unsuitable laser settings
• Using excessive treatment intensity
• Using an inappropriate chemical peel strength
• Using poor technique
• Failing to adapt treatment to the patient's skin response
• Continuing treatment despite clear signs that the skin is being injured

After treatment

Potential failures may include:

• Failing to assess worsening pigmentation
• Failing to recognise burns or persistent redness
• Failing to respond appropriately to another developing complication
• Failing to provide suitable aftercare
• Failing to recommend further medical or dermatological assessment where needed

Hyperpigmentation or hypopigmentation by itself does not establish negligence. Independent medical evidence is usually needed to show both that the care fell below the expected standard and that this caused the lasting damage.

What about hypopigmentation after acne-scar treatment?

Hypopigmentation may occur when treatment affects melanocytes and reduces pigment production. It can be particularly noticeable where lighter areas contrast sharply with the surrounding skin.

Corrective options depend on the cause and extent of the damage. A dermatologist may need to assess whether pigment is likely to return before any further procedure is considered.

Further treatment should not be rushed because additional inflammation can worsen uneven skin tone.

How can pigmentation after acne treatment be managed?

Management should be tailored to the cause and skin type. It may involve sun protection, gentle skin care products, prescription creams or other active ingredients where clinically appropriate.

Possible options may include:

• Topical retinoids: Topical retinoids accelerate cell turnover and can help fade dark patches.
• Azelaic acid: Azelaic acid can treat both acne and hyperpigmentation.
• Niacinamide: Niacinamide can brighten uneven skin tone and support the skin barrier.
• Vitamin C: This may also form part of a treatment plan depending on the person's skin and the type of pigmentation.
• Exfoliating acids: Exfoliating acids can slough off pigmented skin cells and improve pigmentation.

These treatments will not be suitable for everyone, and overly aggressive treatment can cause further irritation.

Patients with significant or persistent pigment change should seek assessment from an appropriately qualified medical professional rather than relying on a single “best treatment” marketed for every skin type.

How can future post-inflammatory hyperpigmentation be reduced?

Reducing inflammation is an important part of limiting the risk of further pigmentation.

Steps that may help include:

• Avoid picking, popping, or squeezing acne lesions to reduce the risk of PIH.
• Treating acne early can reduce the severity and duration of skin inflammation.
• Use daily sun protection: Daily sun protection is crucial to prevent dark marks from worsening.
• Limit UV exposure: UV radiation stimulates melanin production and darkens existing skin marks.
• Keep skincare gentle: A gentle skincare routine may help avoid unnecessary irritation while acne or pigmentation is being managed.

These measures can help reduce further inflammation and prevent existing pigmentation from becoming more noticeable.

What evidence is needed for a negligence claim?

Evidence can help establish what was planned, what treatment was delivered and how the skin changed afterwards.

Useful evidence can include:

• Consultation and treatment records
• Consent forms
• Before-and-after photographs
• Dated photographs showing pigmentation changes
• The treatment plan and laser settings, where available
• Details of the chemical peel used and its strength
• Aftercare instructions
• Messages and emails with the clinic
• GP or dermatology records
• Receipts and records of corrective treatment
• Independent medical expert evidence

Cosmetic Surgery Solicitors' guide to steps to claim compensation after cosmetic surgery goes wrong explains the types of records and evidence that may help support a claim.

Can lasting pigmentation damage be compensated?

If negligence is established, compensation may reflect the physical, emotional and financial impact of the injury.

This can include pain and suffering, visible pigmentation or scarring, psychological harm, the cost of corrective treatment, travel expenses, lost earnings and future treatment needs where supported by evidence.

The amount depends on the individual circumstances. The Cosmetic Surgery Solicitors compensation guide explains some of the factors that may be considered when calculating compensation.