Acne is one of the most common skin conditions in the world, affecting millions of people — from teenagers to adults. Despite how common it is, acne can have a significant impact on self-confidence and quality of life.
In this article, we explain exactly what acne is, what causes it, what it looks like, what actually works, and how to avoid scarring.
What is acne?
Acne (acne vulgaris) is a chronic skin condition that occurs in the oil glands (sebaceous glands) and hair follicles. These glands produce sebum — a natural oil that protects and moisturises the skin. When the oil glands overproduce and dead skin cells clog the pores, an environment is created where bacteria thrive and cause inflammation.
Acne is not contagious and is not caused by poor hygiene, although cleanliness can help manage it.
What does acne look like?
Acne can appear in many forms:
- Blackheads and whiteheads: Plugged pores due to excess oil and dead skin cells. Blackheads are open and dark in colour; whiteheads are closed.
- Pimples (pustules and papules): Red, inflamed bumps that may contain pus.
- Nodules and cysts: Deeper, painful lumps under the skin. These are the most severe forms and carry the greatest risk of scarring.
Acne most commonly appears on the face, back, chest and shoulders — areas with many oil glands.
Not every facial rash is acne. Persistent central redness with visible blood vessels and a tendency to flush — usually without blackheads — points more towards rosacea, while greasy, yellowish scaling around the nose, eyebrows and hairline suggests seborrhoeic dermatitis. The distinction matters, because the treatments are not the same.
When to seek urgent help
Contact a doctor promptly if deep, painful nodules or cysts are getting rapidly worse while you also have a fever, joint pain or feel generally unwell. This can be acne fulminans, which needs urgent specialist treatment. Sudden, severe acne in an adult woman together with excess facial or body hair and irregular periods should also be investigated, as it can point to a hormonal cause such as polycystic ovary syndrome (PCOS).
Why does acne happen?
Acne develops when several factors combine:
What role do hormones play?
They drive oil production. Hormones — particularly androgens like testosterone — stimulate the oil glands to produce more oil. This is why acne typically starts during puberty, and why women often experience breakouts around menstruation, pregnancy or hormonal changes.
How do pores become clogged?
Dead skin cells mix with excess sebum and block the hair follicles. This creates comedones — the characteristic blackheads and whiteheads that are the precursor to inflamed acne.
What do the bacteria do?
The bacterium Cutibacterium acnes lives naturally on the skin, but in clogged pores it thrives and triggers an immune response, causing the characteristic redness and inflammation.
How much do genetics and lifestyle matter?
Genetic factors play a major role. If your parents had severe acne, you are more likely to develop it yourself. Stress, certain medications and diet can also worsen the condition — the best evidence points to high-glycaemic foods such as sugar and refined carbohydrates, and to skimmed milk.
Who gets acne?
Acne is incredibly common and affects most people at some point in their lives:
- Teenagers: Up to 85% of young people aged 12–25 experience acne due to hormonal changes during puberty.
- Adult women: 12–22% of women over 25 have acne, often hormone-related.
- Adult men: Acne in adult men is less frequent than in women, but does occur.
No one is immune. Acne can affect all skin types, ages and backgrounds.
What can you do about acne?
While there is no single universal cure, acne is treatable in most cases. The key is consistent treatment over time:
Over-the-counter products (mild acne)
Benzoyl peroxide, salicylic acid and niacinamide can reduce pimples and oil production.
Prescription treatment (moderate/severe acne)
A topical retinoid combined with benzoyl peroxide is first-line for most inflammatory acne. Oral antibiotics must never be used on their own: they are given alongside benzoyl peroxide or a topical retinoid, and limited to around three months, to reduce the risk of antibiotic resistance. Hormonal treatment such as the combined pill is an option for some women.
Isotretinoin (severe or scarring acne)
Isotretinoin (Roaccutane) is the most effective treatment for severe acne. It is highly teratogenic and must never be taken during pregnancy; women of childbearing potential need pregnancy testing and effective contraception throughout treatment and for one month afterwards. In Denmark, treatment may only be initiated by a dermatologist, who also monitors blood tests and side effects.
Lifestyle
Cut back on sugar, refined carbohydrates and skimmed milk, manage stress, get enough sleep and wash your face twice daily with a gentle cleanser. Washing more often than that irritates the skin without clearing acne.
Avoid
Don't pick or squeeze — it worsens inflammation and increases the risk of scarring.
How long does acne treatment take to work?
Longer than most people expect. A new spot starts forming several weeks before it becomes visible, so any treatment has to work its way through that pipeline before you see a difference. Most treatments — both creams and tablets — need 8–12 weeks of consistent daily use before their effect can be judged.
Skin often looks slightly worse for the first two to four weeks as existing blockages come to the surface. Stopping early is the single most common reason acne treatment appears to fail. Photograph the same area in the same light once a week — progress is far easier to see across a month than from day to day. Once acne is controlled, most people need to continue a maintenance treatment, usually a topical retinoid, to keep it that way.
How can you prevent acne scarring?
By treating inflammation early and leaving the skin alone. Scars form when inflammation reaches deep enough to damage the dermis, so the deeper and longer-lasting a spot is, the greater the risk. Nodules and cysts scar most often, which is why severe acne should be treated rather than waited out. Picking or squeezing pushes inflammation deeper and is the most avoidable cause of scarring there is.
Acne leaves two different kinds of mark that are often confused. Flat red or brown patches left after a spot clears are post-inflammatory pigmentation, not scars — they fade on their own over months, and faster with daily sunscreen, which stops them darkening further. True scars are changes in the skin's texture: small pits, or less commonly raised scars on the chest, shoulders and back. These do not resolve on their own but can be improved with treatments such as microneedling, laser resurfacing or minor surgical techniques, which are best assessed once the acne itself is under control.
Medical classification: Acne is classified as ED80 in the WHO's International Classification of Diseases (ICD-11). It is characterised by comedones, papules and pustules, often related to hormonal changes.
Frequently asked questions
Is acne dangerous?
Acne is not dangerous in a medical sense, but severe untreated acne can leave permanent scars. Early treatment is important.
Can acne go away on its own?
Mild acne can improve over time, but moderate to severe acne typically requires treatment. Waiting it out can result in scarring.
When should I contact a dermatologist?
Contact a dermatologist if over-the-counter products are not helping after 2–3 months, if you develop scars or deep cysts, or if acne is affecting your well-being.
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Disclaimer: This article is for informational purposes only and does not replace professional medical advice. Always consult a doctor or dermatologist for personal guidance and assessment of skin changes.