Acne Vulgaris

How acne develops

Each hair follicle has an oil (sebaceous) gland attached. Together they form a pilosebaceous unit, and acne is a disease of this unit. Four processes work together:

1. Excess sebum: androgens enlarge the oil glands from puberty onward.
2. Abnormal shedding of skin cells: cells lining the follicle stick together and form a plug, the microcomedone, which is invisible at first.
3. Bacterial overgrowth: Cutibacterium acnes (formerly Propionibacterium acnes) multiplies in the oily, low-oxygen plug.
4. Inflammation: the immune system reacts to bacteria and leaking follicle contents, producing red papules and pustules. If the follicle wall ruptures deep in the skin, nodules form.

Treatments target one or more of these steps, which is why combinations work better than single products.

Types of acne

Grades of severity

Dermatologists grade acne as mild (mostly comedones, few papules), moderate (many papules and pustules, few nodules) or severe (many nodules, cysts or scarring). The grade guides treatment more than the number of spots alone. Acne that scars or causes significant distress is treated as more severe.

Other forms

• Hormonal acne: inflammatory spots along the jaw, chin and neck in adult women, often worse before periods.
• Neonatal and infantile acne: in babies, usually mild and temporary.
• Drug-induced acne: uniform pustules after steroids, lithium, some anticonvulsants or anabolic steroids.
• Acne mechanica: where equipment or clothing rubs.
• Occupational acne (chloracne): from contact with industrial oils and certain chemicals, rare.

Causes and risk factors

• genetics: having parents with acne
• puberty and hormonal fluctuations, including menstrual cycles and pregnancy
• polycystic ovary syndrome and other causes of excess androgens
• oily or occlusive skin and hair products
• some medicines and supplements
• high-glycemic diets and dairy in some people
• smoking, linked to adult comedonal acne

Acne is not caused by poor hygiene or dirt, and it is not contagious.

Diagnosis

A doctor diagnoses acne by examining the skin, noting the types of spots, their distribution and any scarring or dark marks. They will ask about skincare, medicines, menstrual history and mood.

Blood tests are not routine. They are considered for women with irregular periods, excess hair, scalp hair loss or sudden severe acne, to check testosterone and other hormones. Doctors also rule out lookalikes such as rosacea, folliculitis and perioral dermatitis. For help telling spots apart and first steps at home, see acne breakouts.

Treatment

Topical treatments (for most acne)

• Retinoids (adapalene, tretinoin, tazarotene, trifarotene): unclog pores and prevent new comedones. They are the foundation of treatment and maintenance. Start every other night to limit irritation. Not for use in pregnancy.
• Benzoyl peroxide: kills C. acnes without resistance. Combining it with any antibiotic reduces resistance.
• Topical antibiotics (clindamycin, erythromycin): always used with benzoyl peroxide, never alone.
• Azelaic acid: antibacterial and helps dark marks. Safe in pregnancy.
• Clascoterone cream: a topical anti-androgen for people aged 12 and over.
• Fixed combinations, such as adapalene with benzoyl peroxide, or clindamycin with benzoyl peroxide and adapalene, improve results and simplify routines.

Oral treatments (moderate to severe acne)

• Oral antibiotics (doxycycline, minocycline, sarecycline): for inflammatory acne, combined with a topical retinoid and benzoyl peroxide, and limited to about 3 to 4 months to reduce resistance. They can cause sun sensitivity.
• Combined oral contraceptives: reduce androgen-driven oil production in women. They take 3 to 6 months to show full benefit.
• Spironolactone: an anti-androgen that is effective for hormonal acne in adult women. It is not used in pregnancy.
• Isotretinoin: the most effective treatment. It shrinks oil glands and produces long-term remission in most people after a 4 to 6 month course. It is used for severe, nodular, scarring or treatment-resistant acne. It causes severe birth defects, so in the US it is prescribed through the iPLEDGE program, with strict contraception and pregnancy testing. Side effects include very dry lips and skin, raised blood fats, and rare mood changes, which need monitoring.

Procedures

• comedone extraction by a professional
• steroid injections into large, painful cysts to shrink them within days
• chemical peels and light-based therapies as add-ons
• treatments for scars once acne is controlled: laser resurfacing, microneedling, subcision and fillers

Treatment by severity

Complications

• Acne scars: ice-pick, rolling and boxcar scars, and raised (hypertrophic or keloid) scars on the chest and back.
• Post-inflammatory hyperpigmentation: dark marks that last months, more common in darker skin.
• Psychological effects: anxiety, depression, social withdrawal and low self-esteem are common and deserve attention in their own right.

Outlook

Acne usually improves by the mid-20s, though it can persist or start in adulthood, particularly in women. With consistent treatment, nearly all acne can be controlled. Maintenance with a topical retinoid after clearing reduces relapses.

Frequently asked questions

What is acne vulgaris?

Acne vulgaris is the medical name for common acne. It is a chronic condition of the hair follicles and oil glands, driven by hormones, extra oil, clogged pores, acne bacteria and inflammation. It causes blackheads, whiteheads, pimples and sometimes deep nodules on the face, chest and back.

What are the different grades of acne?

Acne is graded as mild, mostly blackheads and whiteheads with a few pimples; moderate, many red papules and pustules; or severe, with nodules, cysts or scarring. The grade, along with scarring and the effect on your life, decides which treatments are recommended.

What is the most effective acne treatment?

For mild to moderate acne, combining a topical retinoid with benzoyl peroxide is the most effective approach. For severe, nodular or scarring acne, isotretinoin is the most effective treatment and often gives lasting remission. Hormonal treatments help many adult women.

What is hormonal acne?

Hormonal acne describes acne driven by androgen effects, typically in adult women along the jaw, chin and neck and flaring before periods. It may be linked to polycystic ovary syndrome. Combined birth control pills and spironolactone are often effective.

Does acne go away on its own?

Mild teenage acne often improves by the early to mid-20s, but it can last into adulthood. Waiting is risky for moderate or severe acne, because it can leave permanent scars. Early treatment controls spots and prevents scarring.