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.

View concern guides

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 & Causes

What Causes Hyperpigmentation?

Hyperpigmentation is one of the most common skin concerns, but its causes vary widely. Sun exposure is the most common trigger, but inflammation, hormones, and injury can also play a role. Understanding the cause is the first step to effective treatment.

Hyperpigmentation is a bit like a scar that forms from different types of injuries - sunburn, acne, or hormonal changes can all leave their mark.

The surprising thing is that the same mechanism - overactive melanocytes - can be triggered by so many different things.

So what causes hyperpigmentation?

Think of melanocytes like smoke detectors. They're supposed to go off in response to specific triggers, but sometimes they're too sensitive and go off when they shouldn't.

Quick answerHyperpigmentation is caused by overactive melanocytes that produce excess melanin.

Medically reviewed by Dermatology reviewer · Updated Jul 18, 2026 · 4 min read

Illustration showing different triggers of hyperpigmentation
Most Common CauseSun exposure
Second CauseInflammation (PIH)
Third CauseHormonal changes
Fourth CauseSkin injury
Key PreventionSunscreen

Key answer

Understandable condition

Hyperpigmentation has multiple causes, but sun exposure is the most common. Understanding the cause is key to effective treatment.

Evidence
Strong - Understandable condition
Best for
Anyone wanting to understand why they have hyperpigmentation
Limitation
Those seeking a single cause for all hyperpigmentation

See what the evidence shows

Short version

Story in brief

The primary cause of hyperpigmentation is sun exposure. UV radiation stimulates melanocytes to produce more melanin as a protective response. Over time, this can lead to the development of sunspots and uneven pigmentation.

Inflammation is another common cause. Post-inflammatory hyperpigmentation (PIH) occurs when the skin responds to injury or inflammation - like acne, eczema, or a cut - by overproducing melanin in the affected area.

Hormonal changes can also cause hyperpigmentation. Melasma, which is often triggered by pregnancy or birth control pills, is a form of hyperpigmentation that appears as larger patches on the face. Genetics and medications can also play a role.

Mental model

Visual explanation

Evidence

What the evidence shows

Hyperpigmentation can be triggered by multiple factors, but the common thread is the overactivation of melanocytes. The cause determines the type and the best treatment approach.

  • Sun exposure link

    Sun exposure link

  • Inflammation link

    Inflammation link

  • Hormonal link

    Hormonal link

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

    Most CommonUsually relevant
    Fit signal
    Often useful

    Sun exposure

  • If your goal is

    SecondUse caution
    Fit signal
    Limited evidence

    Inflammation (PIH)

  • If your goal is

    ThirdUse caution
    Fit signal
    Limited evidence

    Hormonal (melasma)

  • If your goal is

    Key PreventionUse caution
    Fit signal
    Limited evidence

    Sunscreen

Research notes already in this guide

  • Sun exposure is the most well-established cause of hyperpigmentation.
  • Research confirms the link between inflammation and PIH.
  • Hormonal causes are well-documented in melasma cases.

Explanation

How it works

  1. Trigger occurs

    Sun exposure, inflammation, hormones, or injury activates melanocytes.

  2. Melanin production increases

    Melanocytes produce more melanin than necessary.

  3. Melanin is transferred

    The excess melanin is transferred to keratinocytes.

  4. Dark patches appear

    The excess melanin becomes visible as dark patches on the skin.

Practical use

How to use it

  1. Identify the cause of your hyperpigmentation

    Understanding the trigger is the first step to effective treatment.

  2. Use sunscreen daily

    Sun protection is essential regardless of the cause.

  3. Treat the underlying condition

    For PIH, control acne or inflammation. For melasma, manage hormones.

Safety

Side effects and cautions

  • Thinking hyperpigmentation is caused by poor hygiene

    It's caused by melanocyte activity, not cleanliness.

  • Believing sun exposure only causes sunspots

    UV radiation can worsen all types of hyperpigmentation.

  • Assuming hyperpigmentation is permanent

    With treatment, it can be significantly improved.

Fit

Who should be careful

  • Those seeking a single cause for all hyperpigmentation

Worth noting

Small details that can change the answer

  • Sun Exposure. UV radiation is the most common cause of hyperpigmentation.
  • Inflammation. PIH is caused by inflammation from acne, eczema, or injury.
  • Hormonal Changes. Melasma is often triggered by pregnancy or hormonal medications.
  • Genetics. Genetics influence susceptibility to hyperpigmentation.

Sun exposure is the most common cause of hyperpigmentation.

Inflammation leads to post-inflammatory hyperpigmentation (PIH).

Hormonal changes can trigger melasma.

Genetics influence susceptibility.

Preventing new triggers is as important as treating existing pigmentation.

Definition

The main causes of hyperpigmentation

Hyperpigmentation can be caused by a variety of triggers, all of which result in overactive melanocytes. Understanding the cause is essential for effective treatment.

  • Sun exposure: UV radiation stimulates melanin production
  • Inflammation: Post-inflammatory hyperpigmentation (PIH)
  • Hormones: Melasma from pregnancy or birth control
  • Skin injury: Healing can leave dark marks
  • Medications: Some drugs can trigger hyperpigmentation

Science

The cellular response to hyperpigmentation triggers

Melanocytes are activated by various signals. UV radiation triggers a signaling cascade that leads to increased melanin production. Inflammatory cytokines from acne or injury can also stimulate melanocytes. Hormonal changes can alter melanocyte activity through estrogen and progesterone receptors.

Melanocyte
A cell in the basal layer of the epidermis that produces melanin.
Inflammatory Cytokines
Signaling molecules released during inflammation that can stimulate melanocytes.

Questions

Frequently asked questions

Does sun exposure cause hyperpigmentation?

Yes, it's the most common cause.

Can acne cause hyperpigmentation?

Yes, acne inflammation often leads to PIH.

Can stress cause hyperpigmentation?

Stress can indirectly affect skin health and pigmentation.

Can certain medications cause hyperpigmentation?

Yes, some drugs can trigger pigmentation changes.

References

Sources

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

  1. Sun exposure is the most well-established cause of hyperpigmentation.
  2. Research confirms the link between inflammation and PIH.
  3. Hormonal causes are well-documented in melasma cases.