Acne affects 40 to 50 million Americans (at some point in their lives) and can range from mild (blackheads and whiteheads) to moderate (pimples) to severe (cysts).While people with any skin type can experience breakouts, acne is commonly caused by oily skin.

The science: “Quite simply, acne is a clogged pore,” explains New York City dermatologist Francesca Fusco, M.D. Each pore is a tiny opening on the surface of the skin that leads to a hair follicle as well as a sebaceous gland. When too much sebum, an oily substance that keeps moisture in the skin, is produced, the pore can get blocked with dead skin cells and bacteria to form a blackhead or whitehead (also called a comedone). If this comedone ruptures, oil and bacteria spread to the surrounding area and cause an inflammation, also known as a pimple.

GALLERY: Skincare Products for Acne

What causes acne?

Hormonal changes can send oil glands into overdrive. Genes play a role, but for the three out of four teenagers who develop acne, this usually has to do with puberty. Adult acne, which generally affects women in their 30s, 40s and 50s, is mostly caused by hormonal fluctuations related to menstrual cycle, pregnancy, birth control pills (especially when you stop taking them) or menopause. In some cases, it can be a sign of polycystic ovary disease.Stress, smoking and diet can cause acne regardless of age or gender. Beauty products that contain oils like synthetic lanolin or petrolatum, greasy hair products like pomade and certain medications including Lithium and cortisteroids are common triggers as well. Also, the combination of bacteria, oil and friction from wearing headbands, helmets with chin straps or cradling your phone can cause contact acne.

Different kinds of acne:MildBlackheads and whiteheads: A blackhead is a partially blocked pore, where trapped dead skin cells, sebum and bacteria have seeped to the surface. (The dark color is not caused by dirt, but the melanin in your skin reacting with the oxygen in the air). A whitehead is caused by the same factors but is a completely blocked pore with a closed surface.

ModeratePapules and pustules: Papules are inflamed red bumps with no visible fluid (i.e. they can’t be popped). Pustules—tender, pus-filled bumps—are plain old pimples.

SevereNodules and cysts: Both are large, hard bumps that have become infected below the surface of the skin. The difference is that cysts are filled with pus and nodules are not. Both types can be quite painful and last for months. Since nodules and cysts can cause scarring even if you don’t pick at them, a dermatologist should always treat this type of acne.

Acne Rosacea: This type of acne generally affects people over the age of 30 and is more common for women. Symptoms include a red rash on cheeks, forehead, nose and chin, visible blood vessels, as well as bumps and pimples. Like cystic acne, a professional should treat.

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Should you see a dermatologist?

Mild and moderate acne is often treatable with over-the-counter products, but if you have more than three large acne bumps, it’s time to see a professional for a skin evaluation, recommends Omaha dermatologist and founder of Dr. Joel Schlessinger.The most effective over-the-counter treatments for mild to moderate acne are salicylic acid, which exfoliates dead skin, benzoyl peroxide, which kills bacteria, and sulfur, which helps reduce redness. Depending on the type of acne, a dermatologist might prescribe antibiotics (like Tetracycline), retinoids (like Differin or Retin A), isotretin (Accutane) or birth control pills to regulate hormones.MORE: Can Food Cause Acne?

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Tips for acne-prone skin:

  • Look for products labeled “non-comedogenic”, “non-acnegenic” and “oil-free.”
  • Avoid products with lanolin, petrolatum or mineral oil, which can clog pores.
  • Pick a cleanser that contains salicylic acid, which both treats and prevents new breakouts.
  • Exfoliate regularly to get rid of dead cells that can clog pores.
  • Wash your face every single night before bed, even if you don’t wear makeup. Oil and grime from the day can clog pores while you sleep.
  • Moisturize with lotion rather a cream. If your skin is very oily, try gel formulas or hydrating serums.
  • Change your pillow case regularly since oil and bacteria can get trapped there while you sleep.
  • Don’t pick at your skin. Squeezing pimples or cysts can make infections spread and lead to scarring.
  • For chronic acne sufferers, try avoiding milk and high glycemic foods like white bread and cookies. They might be a trigger for you. Food causing acne is not a myth! Read more here.
  • Avoid greasy hair products like waxes and pomades.

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