What causes blackheads, and how to stop new ones

A blackhead is a pore plugged with oil and dead skin cells that stays open at the top. That one sentence covers the cause, but it leaves the more useful question: why do some pores clog again and again? This guide explains how the plug forms, why the top turns black, what adds to the clogging, and which habits stop new blackheads. For the full plan to clear the ones you already have, see how to get rid of blackheads.

How a blackhead forms

MedlinePlus, the health information service of the U.S. National Library of Medicine, describes the steps. Each pore on the skin opens into a follicle, the small tube that holds a hair. The follicle also has an oil gland. The oil it releases "helps remove old skin cells and keeps your skin soft."

Problems start when the follicle blocks. MedlinePlus says the glands "can become blocked with a mixture of oil and skin cells," and that this blockage "is called a plug or comedone." Comedone is the medical word for a clogged pore. Doctors use it for both blackheads and whiteheads.

What decides which one you get is the top of the pore. The American Academy of Dermatology (AAD) says that when oil and dead skin cells build up inside a pore, "it widens the opening of the pore and you see a blackhead." Its medical name is open comedo, which means open pore. If the opening closes over the plug, you get a whitehead, a closed comedo. The guide closed comedones covers that closed type in detail.

Doctors who study acne describe a stage before you can see anything. A 2004 review in the journal Clinics in Dermatology explains that the lining of the follicle makes too many skin cells that stick together. This shows up under a microscope as a microcomedone, a clog too small to see, and later "clinically as blackheads, whiteheads, and other forms of comedones." The same review found a link between how severe acne is and the number and size of these tiny clogs.

Why the top turns black

The dark color surprises people, because it looks like dirt. The AAD explains that the color is a chemical reaction: "When the buildup inside the pore reacts with oxygen in the air, the black color appears. This reaction is similar to what happens when a cut-up apple turns brown."

This matters for how you treat blackheads. The AAD's page on acne types says: "The black dots aren't dirt, so resist scrubbing. It will only worsen your acne." Harder washing leaves the plug where it is and adds irritation.

What drives the clog

Four things work together inside a pore. The sources name each of them.

Oil. The AAD says that during puberty, hormones called androgens "increase the size of the skin's oil glands. These glands start making more oil, which can clog pores." The AAD says hormones "may explain why acne is so common in teenagers."

Dead skin cells. Skin sheds cells all the time. In a pore that clogs, those cells stick together with the oil instead of leaving the follicle. The AAD says a whitehead forms when "excess oil and dead skin cells build up and plug the opening of a pore," and a blackhead forms the same way.

Hormones. MedlinePlus lists "hormonal changes that make the skin oilier," which "may be related to puberty, menstrual periods, pregnancy, birth control pills, or stress." The NHS gives a similar list: puberty, periods, menopause and pregnancy.

Bacteria. Bacteria that normally live on the skin can multiply in a pore full of oil. The AAD says that when this happens, inflammation develops "and a pimple appears." A blackhead with no redness around it is a clog without that swelling.

Things that add to blackheads

Some causes are outside your control, such as your age and your genes. MedlinePlus says acne "tends to run in families." Others you can change. The sources name these:

What adds to clogging	What the source says
Oily makeup and skin care	The AAD says oily makeup and skin care products can worsen acne. Makeup can take a few days to 6 months to cause breakouts.
Oily hair products	The AAD says oils in shampoos, conditioners and styling products "can cause tiny breakouts along your hairline and forehead." Pomade is a common example.
Rubbing and pressure	MedlinePlus lists "excessively touching, resting on, or rubbing the skin." The AAD calls acne from sports gear and straps acne mechanica.
Heavy sweating and humidity	MedlinePlus lists both as triggers.
Some medicines	MedlinePlus names steroids, testosterone, estrogen and phenytoin, and some medicine-containing IUDs.
Smoking	The AAD describes a study of women with noticeable whiteheads and blackheads, many of whom smoked.
Too little sleep	The AAD lists it among things that may worsen acne.

The makeup link is easy to miss because of the delay. The AAD says acne cosmetica "can take anywhere from a few days to 6 months" to appear. By then, few people connect the bumps with the product. When a new product arrives in your routine, write down the date. If blackheads or small whiteheads start in the months that follow, that product is the first thing to check. The guide what non-comedogenic means explains how to read those labels.

The AAD describes a study of adult women who had "noticeable whiteheads and blackheads that often covered a large area of their face." Many of them smoked, and "the more cigarettes a woman smoked, the more severe her acne." The AAD adds that other studies found "smokers are more likely to have acne than non-smokers."

What the sources say about dirt, food and stress

Dirt. The AAD says the black specks are the result of oxygen reacting with the plug. Washing harder leaves them in place, and scrubbing makes acne worse.

Chocolate and greasy food. MedlinePlus says: "Research does not show that chocolate, nuts, and greasy foods cause acne." It adds that diets high in refined sugars or dairy products "may be related to acne in some people, but this connection is controversial." The AAD lists "eat certain foods" among things that may worsen acne. The guide does diet cause acne goes through that evidence.

Stress sits in between. The AAD says: "While stress cannot cause acne, stress may worsen existing acne."

Why blackheads come back

Squeezing out a blackhead empties one pore for a while. The oil gland keeps working, and the lining of the follicle keeps shedding cells. The AAD's page on pimple popping says that even after a dermatologist removes them, "Blackheads and whiteheads can return, so you'll need to follow a skin-care plan to prevent new blemishes."

A small, older study shows how fast a pore can fill. In 1976, researchers writing in Archives of Dermatological Research studied sebaceous filaments, thin plugs of skin oil common on the nose. They found that after the filament was squeezed out, "the follicle refills within 30 days." Sebaceous filaments are a normal part of the pore and differ from blackheads, which the guide sebaceous filaments explains. The same holds for blackheads: an emptied pore can fill again.

How to stop new blackheads

The steps below come from AAD pages on skin care habits and treatment:

1. Choose products that will not clog pores. The AAD says to use "only makeup, sunscreen, skin, and hair-care products that are labeled 'non-comedogenic' or 'won't clog pores.'"
2. Remove makeup every night. The AAD says: "Remove your makeup before you go to bed. No exceptions."
3. Wash twice a day and after sweating. Use your fingertips and a gentle cleanser. The AAD says scrubbing "can irritate your skin, causing acne to flare."
4. Keep hair products off your skin. If you use pomade or an oily styling product, keep it away from the hairline and forehead.
5. Pad what rubs. The AAD suggests clean, soft padding between sports equipment and skin, and loose clothes that let sweat escape.
6. Use a treatment that clears pores. The AAD says a retinoid you apply to the skin "works to clear your pores, and can treat blackheads, whiteheads, and some pimples." Adapalene is the one sold without a prescription. The AAD adds that dermatologists may recommend a topical retinoid "as a maintenance treatment" to keep skin clear.
7. Keep going after skin clears. The AAD says to keep using the treatment after clearing, because it helps prevent new breakouts.

The guide adapalene for blackheads and whiteheads explains how to start it. Two areas have their own guides. Blackheads on the nose covers the place they appear most, and blackheads on the back covers the skin where sweat, straps and clothing add to the rubbing. Small white bumps on the nose have their own causes, covered in whiteheads on the nose.

When a "blackhead" is something else

A few conditions look like a large blackhead and have different causes.

• A dilated pore of Winer. A StatPearls review, published through the U.S. National Library of Medicine, describes it as "an asymptomatic, solitary, enlarged pore with a keratin plug." Asymptomatic means it causes no pain or itch. Keratin is the protein in skin cells. It usually appears on the head and neck of middle-aged and older adults, and sometimes on the trunk. It is harmless, and a doctor can remove it by cutting it out.
• A skin cyst. The NHS says skin cysts are round lumps under the skin that "sometimes have a small, dark spot in the middle." The NHS says: "Do not squeeze a skin cyst. If it bursts it could become infected."
• Sebaceous filaments. These are grey or yellowish dots on the nose that are a normal part of oily skin.

When to see a doctor

Blackheads alone are mild acne, and many people clear them with products sold without a prescription. The AAD says to give treatment six to eight weeks to work. See a dermatologist or your family doctor if blackheads have not improved after that, if you also have deep or painful lumps, if you have a lump you cannot identify, or if acne is leaving scars. Skinli gives general education and is not a doctor, so a doctor's advice comes first for anything that hurts, grows or will not clear. If you want a plan built from a photo of your skin, the free Skinli acne plan starts there.