SkincareSafety Guide

Skin

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

View all skin guides

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.

View all products

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.

Conditions & Symptoms

What Do Blocked Sweat Glands Look Like?

Blocked sweat glands, also called heat rash or miliaria, are a common skin complaint, particularly in hot and humid conditions. They are usually easy to recognize once you know what you are looking at.

Blocked sweat glands go by several names: heat rash, prickly heat, miliaria. They all describe the same problem, which is sweat trapped under the skin.

The appearance varies depending on how deeply the sweat ducts are blocked, which is why the same condition can look like clear blisters, red bumps, or firm, deep lumps.

So what do blocked sweat glands actually look like, and how do you treat them?

It is less like an infection spreading and more like a plumbing issue: sweat cannot get out, so it backs up.

Quick answerBlocked sweat glands typically appear as small bumps on the skin.

Medically reviewed by Dermatology reviewer · Updated Sep 11, 2026 · 4 min read

Small red bumps of heat rash on skin
Also CalledHeat rash
AppearanceSmall bumps
Common SitesFolds, covered skin
SensationItchy, prickling
EvidenceGood

Key answer

Recognizable bumps

Blocked sweat glands cause small bumps that vary in appearance by depth.

Evidence
Moderate - Recognizable bumps
Best for
Identifying and treating heat rash
Limitation
Persistent or infected rashes, which need medical care

See what the evidence shows

Short version

Story in brief

Blocked sweat glands, or miliaria, occur when sweat ducts become blocked and sweat leaks into the surrounding skin. The result is a rash that varies in appearance depending on how deeply the ducts are affected.

Miliaria crystallina is the mildest form, causing clear, superficial blisters that are not usually itchy and rupture easily. Miliaria rubra is more common and causes red, itchy bumps with a prickling sensation. Miliaria profunda is the least common, producing deeper, firmer bumps.

The rash most often appears in areas where skin folds or clothing traps heat and moisture, such as the neck, chest, back, armpits, and groin. Cooling the skin and keeping it dry usually resolves the rash within days to weeks.

Mental model

Visual explanation

Evidence

What the evidence shows

The appearance of blocked sweat glands depends on the depth of the blockage; superficial blockage causes clear blisters, while deeper blockage causes red or firm bumps.

  • Small bumps after heat or sweating?

    Cool and dry the skinMost cases resolve with cooling.

  • Itchy, prickling rash?

    Avoid heavy creams and wear loose clothing

  • Persistent or worsening?

    See a healthcare provider

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

    Also calledUse caution
    Fit signal
    Limited evidence

    Heat rash

  • If your goal is

    AppearanceUse caution
    Fit signal
    Limited evidence

    Small bumps

  • If your goal is

    Common sitesUse caution
    Fit signal
    Limited evidence

    Folds, covered skin

  • If your goal is

    TreatmentUsually relevant
    Fit signal
    Often useful

    Cool and dry

Explanation

How it works

  1. Heat and humidity

    Sweating increases to cool the body.

  2. Ducts become blocked

    Sweat ducts narrow or close due to heat, friction, or debris.

  3. Sweat leaks into skin

    Trapped sweat irritates surrounding tissue.

  4. Bumps form

    The rash appears in affected areas.

Practical use

How to use it

  1. Cool and dry the skin

    Move to a cooler environment and let the area air out.

  2. Wear breathable clothing

    Loose fabrics reduce heat and moisture.

  3. Seek care if persistent

    If the rash does not improve, consult a healthcare provider.

Safety

Side effects and cautions

  • Confusing heat rash with other conditions

    Its appearance and location help distinguish it; persistent rashes should be evaluated.

  • Applying heavy creams to the affected area

    These can worsen blockage; keep skin cool and dry.

  • Scratching the bumps

    Can cause damage and infection.

Fit

Who should be careful

  • Persistent or infected rashes, which need medical care

Worth noting

Small details that can change the answer

  • Cause. Sweat ducts become blocked and sweat leaks into the skin.
  • Types. Miliaria crystallina, rubra, and profunda vary by depth.
  • Appearance. Clear blisters, red bumps, or firm lumps.
  • Sensation. Itching or prickling is common.

Blocked sweat glands cause small bumps on the skin.

Appearance varies by depth: clear blisters, red bumps, or firm lumps.

They most often appear in skin folds and covered areas.

Cooling and drying the skin is the main treatment.

Persistent or worsening rashes should be evaluated.

Definition

What blocked sweat glands are

Blocked sweat glands, also called miliaria or heat rash, occur when sweat ducts become obstructed and sweat leaks into the surrounding skin. This causes small bumps and irritation.

Explanation

What they look like

The appearance depends on how deeply the sweat ducts are blocked.

Dos Donts

Managing blocked sweat glands

Do

Cool the skin

Reduces sweating and allows the ducts to clear.

Keep the area dry

Prevents further blockage.

Wear loose, breathable clothing

Reduces heat and moisture trapping.

Avoid

Apply heavy creams

Can worsen blockage.

Scratch the bumps

Can damage skin and increase infection risk.

Stay in hot environments

Keeps the trigger present.

Questions

Frequently asked questions

What does heat rash look like?

It can appear as clear blisters, red itchy bumps, or deeper firm bumps, depending on the type.

Where do blocked sweat glands usually appear?

In skin folds and areas covered by clothing, such as the neck, chest, back, and groin.

How long does heat rash last?

Most cases resolve within days to a couple of weeks once the skin is kept cool and dry.

When should I see a doctor?

If the rash persists, worsens, or shows signs of infection.