Active ingredients in acne products

Acne products work in different ways, depending on their active ingredients. Some work by killing acne-causing bacteria. Others remove excess oil from the skin or speed the growth of new skin cells and the removal of dead skin cells. Some acne products try to do all these things.

Here are common active ingredients found in acne products used on the skin and how they work.

• Benzoyl peroxide. This ingredient kills bacteria that cause acne, helps remove excess oil from the skin and removes dead skin cells, which can clog pores. Benzoyl peroxide products that you can buy without a prescription are available in strengths from 2.5% to 10%. Studies show that lower strength products are as effective as higher strength preparations. Consider starting with a lower strength (2.5%) water-based product to lower the risk of side effects.

  Possible side effects include dry skin, scaling, irritation, burning and stinging, especially if you have sensitive skin. Be careful when applying benzoyl peroxide, as it can bleach hair and clothing. It has no bleaching effect on the dark patches that can linger after acne clears (postinflammatory hyperpigmentation).

• Adapalene. This ingredient is a retinoid that helps unclog pores and prevent new breakouts. Adapalene gel (Differin) is available without a prescription at a strength of 0.1%. Don't apply this product to skin that has a cut, sunburn or eczema rash. You might feel a slight stinging when the gel is applied, but it soon goes away. Other possible side effects include dry skin, scaling and inflamed skin. Use a nonoily (noncomedogenic) moisturizer to ease these symptoms.

• Salicylic acid. This ingredient may help unclog pores and prevent new breakouts.

  Salicylic acid products that you can buy without a prescription are available in strengths from 0.5% to 2% as both leave-on and wash-off products. Possible side effects include mild stinging, skin discoloration and minor skin irritation.

• Azelaic acid. This ingredient helps prevent pores from becoming plugged and is mildly antibacterial. Nonprescription azelaic acid products are available in 10% strength. Azelaic acid also helps correct dark spots that can linger after acne clears (postinflammatory hyperpigmentation).
• Alpha hydroxy acids. Alpha hydroxy acids are synthetic versions of acids derived from sugar-containing fruits, sugar cane or milk. Two types of alpha hydroxy acids that are used in nonprescription acne products are glycolic acid and lactic acid. They treat acne by removing dead skin cells and calming inflamed skin. Alpha hydroxy acids also spur the growth of new, smoother skin. This helps improve the look of acne scars and pores.