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.

View ingredient questions

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.

View routine questions

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.

View learning guides

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 & Science

What Causes Dry Skin?

Dry skin is not simply about missing moisture - it's a sign that the skin's barrier is struggling to do its job. The causes are more varied and interesting than just "not enough moisturizer."

Most people think dry skin is just about needing more moisturizer, but that's like saying a leaky roof needs more buckets.

The real question is why the skin is letting water out in the first place.

So what actually causes skin to become dry, flaky, and uncomfortable?

If skin is like a brick wall, the sebum is the mortar and the barrier is the sealant. Dry skin happens when the mortar is thin and the sealant is cracked - water gets out, and irritants get in.

Quick answerDry skin is caused by a combination of low sebum production, a compromised barrier that allows moisture to escape, and environmental factors that accelerate water loss.

Medically reviewed by Dermatology reviewer · Updated Jul 18, 2026 · 6 min read

Close-up of dry, flaky skin texture showing visible dehydration
Skin TypeDry
Primary CauseBarrier dysfunction, low sebum
Key SymptomsFlaking, tightness, roughness
Environmental FactorsClimate, heating, humidity
Treatment FocusBarrier repair, hydration

Key answer

Primary cause: barrier compromise

Dry skin is a sign that the barrier needs support - the solution is targeted care.

Evidence
Strong - Primary cause: barrier compromise
Best for
Identifying the root cause of dryness
Limitation
Assuming a single moisturizer will solve everything

See what the evidence shows

Short version

Story in brief

The skin has a remarkable ability to hold water. The stratum corneum, or outermost layer, is designed to retain moisture while blocking out environmental aggressors. When this system functions properly, skin feels comfortable and looks healthy. Dry skin occurs when the barrier is compromised or when sebum production is insufficient to support it.

A compromised barrier allows water to escape at an accelerated rate through a process called trans-epidermal water loss (TEWL). This triggers a cascade of visible problems: tightness, flaking, roughness, and a loss of that healthy, bouncy glow. Dry skin is often also less resilient - it may feel sensitive, itchy, or reactive.

The causes of dry skin fall into three main categories: internal factors like genetics and hormones, external factors like climate and skincare, and behavioral factors like lifestyle choices. Understanding which ones affect you is the first step to choosing the right care.

Mental model

Visual explanation

Evidence

What the evidence shows

How well research supports the causes of dry skin.

  • Low sebum → dry skin

    Well-established link

  • Barrier compromise → TEWL

    Consistent research findings

  • Environmental triggers

    Well-documented

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

    Main issueDepends
    Fit signal
    Possible fit

    Barrier compromise + low sebum

  • If your goal is

    Water lossDepends
    Fit signal
    Possible fit

    Higher than normal

  • If your goal is

    Primary treatmentUse caution
    Fit signal
    Limited evidence

    Barrier repair

  • If your goal is

    Recovery timeUse caution
    Fit signal
    Limited evidence

    Several weeks

Research notes already in this guide

  • The relationship between low sebum production and dry skin is well established.
  • TEWL rates consistently correlate with dry skin symptoms.
  • Barrier-repair strategies are supported by extensive research.
  • Climate and seasonal changes are recognized triggers in dermatological literature.

Explanation

How it works

From healthy to dry skin in four steps.

  1. Low sebum production

    Sebaceous glands produce less oil, leaving the barrier under-supported.

  2. Barrier becomes less cohesive

    Without adequate oil, the barrier cells lose their tight packing.

  3. Water escapes

    Moisture leaves the skin faster than it can be replenished.

  4. Skin dries out

    Tightness, flaking, and roughness become noticeable.

Practical use

How to use it

  1. Switch to a gentle, soap-free cleanser

    Avoid sulfates and stripping detergents that remove natural oils.

  2. Use barrier-supporting moisturizers

    Look for ceramides, cholesterol, and fatty acids.

  3. Protect against environmental dryness

    Use a humidifier in dry conditions and cover up in cold weather.

Safety

Side effects and cautions

  • Using alcohol-based products that evaporate and remove moisture

    Choose alcohol-free, hydrating formulas instead.

  • Taking long, hot showers that strip oils

    Keep showers brief and use lukewarm water.

  • Assuming a richer moisturizer alone will fix everything

    If the barrier is compromised, moisturizer alone isn't enough - you need barrier-supporting ingredients too.

Fit

Who should be careful

  • Assuming a single moisturizer will solve everything

Worth noting

Small details that can change the answer

  • Sebum Role. Sebum, the skin's natural oil, forms part of the barrier that prevents water loss. Low sebum production is a hallmark of dry skin.
  • TEWL. Trans-epidermal water loss is the rate at which water evaporates from skin - higher rates indicate a more compromised barrier.
  • Genetics. Some people have a genetic predisposition to lower sebum production and a thinner barrier.
  • Climate Impact. Low humidity environments can increase TEWL by as much as 25 percent.

Dry skin is caused by a combination of low sebum and a compromised barrier that allows water loss.

The primary issue is water loss (TEWL), not just oil deficiency.

Genetics, hormones, climate, and skincare habits all influence dryness.

Treatment requires barrier repair, not just moisturizing.

Consistent, gentle care is essential for managing dry skin.

Definition

What "dry" actually means

In dermatological terms, dry skin (xerosis) is defined by low sebum production. Sebum is the skin's natural moisturizing oil, produced by sebaceous glands. It helps form the protective barrier on the skin's surface. When sebum production is low, the barrier is less effective at retaining water, and the skin loses moisture faster than it can be replenished.

Explanation

Internal causes

Genetics play a significant role in determining sebum production levels. Some people simply produce less oil than others. Hormonal changes also influence sebum production - estrogen promotes sebum production, while androgen levels affect it differently. This is why dry skin is more common in older adults and in people with certain hormonal conditions.

Explanation

External and environmental causes

External factors are often the decisive trigger that pushes skin from comfortable to uncomfortable dry. Low humidity environments, especially in winter with indoor heating, can dramatically increase water loss. Harsh cleansers that strip natural oils, long hot showers, and aggressive exfoliation are common culprits. Even sun exposure can dry out the skin over time.

Questions

Frequently asked questions

Is dry skin the same as dehydrated skin?

No - dry skin refers to low oil production, while dehydrated skin refers to low water content. They can occur together or separately.

Can dry skin be permanent?

For some people, dry skin is a chronic condition managed with consistent care; for others, it may be temporary.

Does drinking more water help dry skin?

Hydration supports overall health, but dry skin is primarily a barrier and sebum issue - drinking water alone won't fix it.

Can diet affect dry skin?

Certain nutritional deficiencies, particularly in essential fatty acids, can contribute to dry skin.

References

Sources

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

  1. The relationship between low sebum production and dry skin is well established.
  2. TEWL rates consistently correlate with dry skin symptoms.
  3. Barrier-repair strategies are supported by extensive research.
  4. Climate and seasonal changes are recognized triggers in dermatological literature.