SkincareSafety Guide

Skin

Understand your skin type, tone, and what your skin is doing.

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Start here

Skin typesThe main skin types and how they differ.Find your skin typeA practical identification guide.What different skin types look likeVisual differences between common skin types.

Common skin questions

Oily skinWhat oily skin means and how to read it.Skin type changesHow skin type can shift over time.Skin type and ageHow visible aging differs by skin type.
Not sure where to start?Use the skin-type guide before choosing routines or ingredients.

Concerns

Start from a skin problem or visible change.

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Oil and acne

Why oily skin happensThe main drivers behind excess oil.Oily skin and acneHow oil can contribute to breakouts.Can oily skin cause acne?A direct answer to the oil-acne link.

Changes and warning signs

Stress and oily skinHow stress may affect oiliness.Dehydration and oilinessWhy skin can feel oily and dehydrated.Skin cancer signsVisual signs that need professional attention.
Looking for a solution?Start with what oily skin actually needs before adding stronger products.

Ingredients

Understand what ingredients do and whether they fit your skin.

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Explore ingredients

NiacinamideA practical ingredient overview.Vitamin C serumWho can use vitamin C and when to be careful.RetinolHow retinol fits different skin types.

Use safely

Salicylic acidWhere this acne-focused ingredient fits.Niacinamide for all skin typesSuitability across skin types.Ingredient comparisonsUse comparisons to avoid mismatched decisions.
Can my skin use this?Browse compatibility questions before adding a new active.

Routines

Turn skin information into daily decisions.

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Daily basics

Does every skin type need moisturizer?A basic routine decision.Does every skin type need sunscreen?Where SPF fits in daily care.What oily skin needsA simple care direction for oily skin.

Adjust over time

Skin changes with ageWhen your routine may need to change.Seasonal skin changesHow weather affects skin behavior.Korean skincare approachWhat is useful beneath the trend.
Starting from scratch?Begin with moisturizer, sunscreen, and one skin-specific need.

Products

A small selection of skincare products recommended by OuterDerm for simple, effective everyday routines.

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Recommended picks

Daily SunscreenDaily UV protection that has to be wearable enough to stick with.Azelaic AcidA focused 10% azelaic acid when uneven tone or blemish marks are the concern.Gentle CleanserComfortable cleansing when tight or squeaky skin is a warning sign.
Not sure where to start?Browse three carefully selected essentials, then ask on WhatsApp before you order.

Learn

Go deeper into skin science, myths, evidence, and safety.

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Hazardous ingredients

Safety hubStart with mercury, steroids, PPD and other hazardous substances.Ingredient safety indexBrowse Phase 1 and Phase 2 hazardous ingredients.Mercury in whitening creamsLabel names, Punjab alerts, and what to do now.

Product literacy

Product literacy hubHow to read labels, claims, and INCI lists before you buy.How to read an ingredient labelINCI order, Parfum, and missing-list red flags.Fragrance-free vs unscentedHow to verify a fragrance-free claim on the ingredient list.How to choose sunscreenBroad spectrum, wearability, and a readable pack — not a fairness claim.

Skin science

Skin color geneticsHow inherited traits shape skin color.Skin color typesHow skin tone is commonly grouped.Are skin types genetic?What genetics can and cannot explain.

Evidence and myths

Can all skin types tan?Tanning, risk, and skin type.Is oily skin good or bad?A balanced view of oily skin.Why Korean skin looks flawlessTrend claims translated into practical basics.
Want the evidence layer?Use why-guides when you want causes, mechanisms, and context.

Skin Conditions & Post-Acne Care

How to Treat Post-Inflammatory Hyperpigmentation

Post-inflammatory hyperpigmentation (PIH) is the medical term for those dark marks left behind after a pimple heals. They're stubborn, frustrating, and surprisingly common. Here's how to fade them.

Quick answerPost-inflammatory hyperpigmentation (PIH) is treated with a combination approach: use vitamin C or niacinamide to inhibit melanin production or transfer, apply a retinoid to speed cell turnover, and always use sunscreen to prevent further darkening.

Medically reviewed by Dermatology reviewer · Updated Jul 18, 2026 · 5 min read

Fading post-inflammatory hyperpigmentation marks on skin
ConditionPost-inflammatory hyperpigmentation (PIH)
TriggerInflammation (acne, injury, rash)
Key IngredientsVitamin C, niacinamide, retinoids
Essential StepSunscreen - always
Evidence LevelStrong

Key answer

Combination approach works best

Treating PIH requires a combination of prevention, melanin inhibition, and cell turnover - plus essential sunscreen. Results take 8-16 weeks.

Evidence
Strong - Combination approach works best
Best for
Post-acne marks and pigmentation after inflammation
Limitation
Textural scars

See what the evidence shows

Short version

Story in brief

Post-inflammatory hyperpigmentation occurs when inflammation triggers melanocytes to produce extra melanin. This can happen after a pimple, a bug bite, a rash, or any kind of skin injury. The resulting dark mark is flat - it's pigment, not texture.

The key to treating PIH is understanding that it's a pigment issue, not a structural one. It responds to brightening ingredients that inhibit melanin production or speed its removal.

Prevention is also essential. Treating the underlying inflammation quickly (with acne treatments or anti-inflammatory products) and avoiding picking or squeezing pimples can prevent PIH from forming in the first place.

Mental model

Visual explanation

Evidence

What the evidence shows

PIH is the skin's pigment response to inflammation. The best treatment is two-part: prevent it by managing inflammation, and fade it with brightening ingredients once it appears.

  • Ingredient Evidence

    Vitamin C, niacinamide, and retinoids have strong evidence for PIH.

  • Combination Evidence

    Combination therapy is more effective than single ingredients.

  • Clinical Consensus

    Dermatologists recommend combination approaches for PIH.

Use this section to decide

Does this advice apply to me?

Find the concern or goal closest to yours, then use the fit signal to decide how much weight to give this guide.
Strong fit means the advice is central to that goal.Depends means formula, tolerance, or context matters more.Use caution means do not treat it as the main answer.

  • If your goal is

    Vitamin CDepends
    Fit signal
    Possible fit

    Strong melanin inhibitor

  • If your goal is

    NiacinamideDepends
    Fit signal
    Possible fit

    Excellent transfer blocker

  • If your goal is

    RetinoidsDepends
    Fit signal
    Possible fit

    Speeds pigment removal

  • If your goal is

    SunscreenUsually relevant
    Fit signal
    Often useful

    Essential for success

  • If your goal is

    PreventionUsually relevant
    Fit signal
    Often useful

    Most effective strategy

Research notes already in this guide

  • Studies show vitamin C and niacinamide are effective for PIH.
  • Research confirms retinoids accelerate fading of post-inflammatory marks.
  • Sunscreen has been shown to prevent PIH from worsening and recurring.
  • Dermatologists recommend combination therapy for PIH.

Explanation

How it works

  1. Prevent further inflammation

    Treat the underlying acne or skin condition to stop new PIH from forming.

  2. Inhibit melanin production

    Use vitamin C or azelaic acid to reduce melanin production.

  3. Block melanin transfer

    Use niacinamide to prevent melanin from reaching the skin's surface.

  4. Speed pigment removal

    Use retinoids to accelerate cell turnover and remove pigmented cells.

Expected results

Results and timeframe

PIH takes 8-16 weeks to fade with consistent treatment.

Practical use

How to use it

  1. Prevent new PIH

    Treat acne or inflammation early and avoid picking.

  2. Use brightening ingredients

    Apply vitamin C, niacinamide, and a retinoid consistently.

  3. Use sunscreen daily

    SPF 30+ every day to prevent marks from darkening.

Safety

Side effects and cautions

  • Picking or squeezing pimples, which creates more inflammation and PIH

    Leave pimples alone and treat them gently.

  • Using aggressive products on PIH and causing more inflammation

    Gentle treatment is better - irritation worsens pigmentation.

  • Expecting quick results

    PIH takes 8-16 weeks to show significant improvement.

Fit

Who should be careful

  • Textural scars

Worth noting

Small details that can change the answer

  • PIH Mechanism. Inflammation stimulates melanocytes to produce excess melanin.
  • Skin Tone Factor. PIH is more common and more persistent in darker skin types.
  • Prevention Key. Early treatment of inflammation can prevent PIH from forming.
  • Treatment Duration. PIH typically takes 3-12 months to fade with appropriate treatment.

PIH is a pigment response to inflammation, not a structural scar.

The best treatment is a combination of prevention and fading strategies.

Use vitamin C, niacinamide, retinoids, and sunscreen daily.

Prevention is key - treat inflammation early and avoid picking.

Definition

What is post-inflammatory hyperpigmentation?

PIH is a flat area of darkened skin that appears after inflammation. It's caused by excess melanin production in response to inflammatory signals from conditions like acne, eczema, or injury. Unlike scars, PIH is pigment, not texture.

  • Flat, pigmented marks
  • Caused by inflammation
  • More common in darker skin
  • Can fade over time

Questions

Frequently asked questions

How long does post-inflammatory hyperpigmentation take to fade?

With treatment, PIH typically fades significantly in 8-16 weeks.

Does post-inflammatory hyperpigmentation go away on its own?

It can fade slowly over months to years, but treatment speeds the process.

Is PIH the same as acne scars?

No - PIH is pigment (flat marks), scars are texture (indentations or raised areas).

Can I get PIH from any kind of inflammation?

Yes - any skin inflammation, including bug bites, rashes, and burns, can cause PIH.

References

Sources

The notes below are drawn from the evidence already cited in this guide. They are not a complete bibliography.

  1. Studies show vitamin C and niacinamide are effective for PIH.
  2. Research confirms retinoids accelerate fading of post-inflammatory marks.
  3. Sunscreen has been shown to prevent PIH from worsening and recurring.
  4. Dermatologists recommend combination therapy for PIH.