Consider benzoyl peroxide the How To Treat Acne 101 ingredient; your first line of defense. It works by reducing the amount of pimple-causing bacteria and excess oil from your skin.

Used with salicylic acid, it's usually so effective Day recommends beginning with over-the-counter doses of each. Only then -- if you don't see a difference in a couple of weeks -- it may be a sign that you should see a dermatologist for a more intensive acne treatment regimen.

Benzoyl peroxide is widely available in a number of gels, creams and lotions, in concentrations between 2.5 percent and 10 percent. Since it can cause red and scaly skin irritation if you have sensitive skin you may want to start with the lowest concentration and work upwards. Some research actually suggests that lower doses of benzoyl peroxide are just as effective as the higher ones. Adult acne sufferers take heed: your skin becomes thinner as you age so you want to treat it as gently as possible.

Try: Neutrogena On the Spot Acne Treatment, $5.99. Another great option: Proactiv Emergency Blemish Relief, $46.

Salicylic acid, also known as beta hydroxy acid (BHA), is one of those multitasking skin care ingredients that can seem like magic. It opens clogged pores, neutralizes bacteria within and helps constrict pore diameter, which keeps pores from clogging up again. For an over-the-counter blemish buster, look for a concentration of 2 percent salicylic acid. "For many patients, if your breakouts are not causing scarring, this may be all the treatment that's needed," says Day.

Try: Philosophy Clear Days Ahead Fast-Acting Salicylic Acid Spot Treatment, $18. Or try Olay Fresh Effects Clear Skin Spot Zinger, $7.99.

Often avoided for causing red, flaky, burning skin, retinol, a derivative of vitamin A, is one of the most powerful acne eradicators -- and skin care ingredients -- on the market. That's because it not only unclogs blocked pores and removes dead cells that cause pimples, it also promotes the growth of healthy skin, reducing wrinkles and age spots. It's available for acne in over-the-counter concentrations, or you can get super-strength trentinoin from your dermatologist in the form of Retin-A. (For anti-aging, ask your dermatologist about Renova.)

Topical retinoids come in cream, gel and liquid forms, usually applied in the evening to help your body deal with any irritation. If you do get redness, doctors advise starting out by applying it every other night.

Try: Skinceuticals Retinol 0.5, $57. Or, Curology, which lets you get a prescription strength retinol through a dermatologist online.

Plant-based oils have come out of the closet for oily skin. "There is a world of oils that are great for facial skin," says Dr. Day. "You don't have to look for 'oil-free' anymore." Plant-based oils can not only provide soothing, hydrating and calming benefits to acne-prone skin, they can also be antibacterial, she says. The key is to make sure you are using oils that are non-occlusive (do not clog pores) and non-greasy. (In other words, avoid petrolatum and mineral oils!) One of the best oils for blemished skin is the humble and inexpensive coconut oil, says Day, which is both hydrating and anti-inflammatory.

Try: For an at-home natural acne treatment: Mix a drop of coconut oil with equal parts honey, an antiseptic, and aloe, an anti-inflammatory that will also help with pain and itch. Apply to pimples as a spot treatment. Rinse off after an hour.

Sulfur works by suppressing the bacteria that causes pimples, and it can also unclog pores. Because it can be very drying (and has a strong smell), it's best to use as a spot treatment or mask that is rinsed off the face.

Try: Murad Acne Spot Treatment, $18, is a powerful pimple blocker that can be applied to full-blown pimples or a blemish you feel coming on before it shows. It contains sulfur (2 percent) and salicylic acid -- a double whammy. Dr. Dennis Gross Skincare Clarifying Colloidal Sulfur Mask, $42, contains sulfur, clay and retinol to fight acne, oil-production and wrinkles.