Acne and Pimples

How pimples form

Every pore contains a hair follicle and a sebaceous gland that produces an oil called sebum. Four things combine to cause a pimple:

1. Extra oil: androgen hormones, which rise at puberty, enlarge the oil glands.
2. Clogged pores: skin cells lining the follicle stick together instead of shedding, forming a plug called a comedone.
3. Bacteria: Cutibacterium acnes, which normally lives on skin, multiplies in the trapped oil.
4. Inflammation: the immune system reacts, causing redness, swelling and pus.

Acne appears where oil glands are densest: the face, forehead, chest, upper back and shoulders.

Types of pimples

Acne with only comedones is mild. Many papules and pustules is moderate. Nodules and cysts, or any scarring, is severe.

What causes pimples and breakouts

• Hormones: puberty, the days before a period, pregnancy, starting or stopping hormonal contraception, and polycystic ovary syndrome. Hormonal acne in adult women typically affects the jawline and chin.
• Genetics: acne tends to run in families.
• Medicines: corticosteroids, anabolic steroids and testosterone, lithium, some anti-seizure medicines, and some progestin-only contraceptives.
• Pore-clogging products: heavy creams, oily hair products and makeup. Look for "non-comedogenic".
• Friction and pressure: helmets, chin straps, backpacks, phones and face masks ("acne mechanica").
• Diet: high-glycemic foods (sugary foods, white bread) and skim milk are linked to worse acne in some studies. Chocolate and greasy food on the skin have weaker evidence.
• Stress: can worsen existing acne.
• Picking and squeezing: pushes inflammation deeper and causes scars and dark marks.

Dirt does not cause acne. Scrubbing hard makes it worse.

Conditions that look like acne

• Rosacea: redness, flushing and pimples on the cheeks and nose in adults, without blackheads.
• Folliculitis: itchy pus bumps around hair follicles, often after shaving or hot tubs. Fungal folliculitis causes uniform itchy bumps on the chest and back.
• Perioral dermatitis: small red bumps around the mouth and nose, often triggered by steroid creams.
• Hidradenitis suppurativa: painful lumps in the armpits, groin and under the breasts.
• Keratosis pilaris: rough, tiny bumps on the upper arms.

How to treat pimples

Over-the-counter treatments

• Benzoyl peroxide (2.5% to 5%): kills acne bacteria and reduces inflammation. It can bleach towels and clothing. Lower strengths irritate less and work as well.
• Adapalene 0.1% gel: a retinoid that unclogs pores and prevents new pimples. Apply a pea-sized amount to the whole area at night. Expect some dryness and possibly a flare in the first few weeks.
• Salicylic acid: helps unclog pores, mainly for blackheads and whiteheads.
• Azelaic acid: reduces pimples and dark marks, and is safe in pregnancy.

Apply treatments to the whole acne-prone area, not just individual spots, because they prevent new pimples as well as treating current ones. Give each regimen 6 to 12 weeks before judging it.

Prescription treatments

• Stronger topical retinoids (tretinoin, tazarotene) and combination gels with benzoyl peroxide and an antibiotic such as clindamycin.
• Oral antibiotics (doxycycline or minocycline) for moderate inflammatory acne, used for about 3 months and always with benzoyl peroxide to limit resistance.
• Hormonal treatments for women: combined birth control pills and spironolactone.
• Isotretinoin for severe, scarring or treatment-resistant acne. It can produce long-term remission but causes birth defects, so strict pregnancy prevention is required. Mood should be monitored.
• Cortisone injection into a single large, painful cyst, done by a dermatologist, flattens it within a day or two.

Daily care

• Wash twice a day and after sweating with a gentle cleanser and lukewarm water.
• Use a non-comedogenic moisturizer and sunscreen. Many acne treatments make skin more sun-sensitive.
• Do not pick, pop or squeeze pimples.
• Wash pillowcases, phone screens and hats regularly.
• Shampoo regularly if you have oily hair that touches your face.

A hydrocolloid "pimple patch" can help a pustule drain and stop you picking.

Acne scars and dark marks

Inflamed pimples can leave red or purple marks, dark brown marks (post-inflammatory hyperpigmentation, more common in darker skin) or permanent acne scars. Marks fade over months with sun protection, azelaic acid or retinoids. Scars need procedures such as microneedling, laser or chemical peels. Treating acne early is the best way to prevent scarring.

Frequently asked questions

What is the difference between acne and pimples?

A pimple is a single inflamed spot. Acne is the skin condition that causes repeated pimples, blackheads and whiteheads over time. Doctors call it acne vulgaris. Someone with an occasional pimple does not necessarily have acne.

How do I get rid of a pimple overnight?

You usually cannot, but you can make it less red and sore. Apply benzoyl peroxide or a hydrocolloid patch, and do not squeeze it. For a large, painful cyst before an important event, a dermatologist can inject a small dose of cortisone, which flattens it within 1 to 2 days.

Is it bad to pop pimples?

Yes. Squeezing pushes bacteria and oil deeper, increases inflammation and raises the risk of infection, dark marks and scars. Pimples near the nose and upper lip are particularly risky. Let them heal or have a professional extract blackheads safely.

What causes hormonal acne in adults?

Adult hormonal acne usually appears on the jawline, chin and neck and flares before periods. It is driven by sensitivity to androgens. It can also be a sign of PCOS, especially with irregular periods and extra hair growth. Combined birth control pills or spironolactone often help.

Does diet cause acne?

Diet is a minor factor for most people. High-sugar and high-glycemic foods and skim milk have been linked to worse acne in some studies. Chocolate and greasy food have weaker evidence. Cutting out whole food groups is rarely needed. Proven skin treatments make a much larger difference.