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Everything You Need to Know About Benzoyl Peroxide

Benzoyl Peroxide Is a Topical Acne Medication That Kills Bacteria, Exfoliates the Skin, Reduces Inflammation, and Clears Comedones (Clogged Pores)

By: Dan Kern, Acne.org Founder & CSO
Last updated: April 26, 2020

The Essential Information

Benzoyl peroxide is a common topical acne treatment that is found in both over-the-counter as well as prescription products with concentrations ranging from 2.5 - 10%.

How It Works:

  • Eradicates bacteria - it kills over 99% of bacteria almost immediately
  • Exfoliates the skin - it is a drying agent that helps keep the skin turning over
  • Reduces inflammation - this is not yet proven, but is likely
  • Clears clogged pores - it helps unclog pores and prevents new clogs

Side Effects:

It takes approximately one month for the skin to become accustomed to benzoyl peroxide, and dermatologists refer to the discomfort during this initial time period as the "hardening effect" of benzoyl peroxide. This is why it is important to start with only a pea-size amount of benzoyl peroxide once per day for the first week, and only then begin slowly ramping up the dosage and frequency. Side effects include:

  • Redness
  • Dryness
  • Peeling
  • Burning
  • Itching
  • Contact dermatitis (a red, itchy rash), especially in the first few weeks of use

Even after the hardening effect subsides, benzoyl peroxide will continue drying the skin, so a moisturizer should be used after each benzoyl peroxide application.

How to Get Benzoyl Peroxide to Work Its Best: Studies show benzoyl peroxide clearing the skin by approximately 50%, however, when used within a proper regimen, it reliably and completely clears the skin in just about everyone. A proper regimen consists of using 2.5% benzoyl peroxide and slowly ramping up the dosage so that after 1 month you are using a lot of it. Here are the full instructions to make sure benzoyl peroxide will completely clear you up.

The Science

What Is Benzoyl Peroxide?

Benzoyl peroxide is a white, grainy/powdery substance that has been used in several industries since the early 20th century. The first time benzoyl peroxide was used as a medication was in 1905, when it was used as an antiseptic treatment for wounds. After this, it continued to be used to treat a variety of conditions, including burns and leg ulcers. Benzoyl peroxide was first used to treat acne in 1965 and since then has been increasingly relied on to treat acne, either alone or in combination with other anti-acne medications, such as retinoids. When used to treat acne today, benzoyl peroxide is found in both over-the-counter and prescription products at concentrations ranging from 2.5 - 10%.1-3

How Benzoyl Peroxide Helps Clear Acne

Benzoyl peroxide works in three ways to treat acne. It:

  1. Reduces bacteria: Benzoyl peroxide is an exceptional antibacterial agent, and can kill 99.9% of bacteria almost immediately. In acne, the bacteria C. acnes grows inside acne lesions, and the byproducts of these bacteria end up causing inflammation in the skin, which shows up as the redness and soreness we see in acne lesions. Once benzoyl peroxide is applied to the skin, it quickly absorbs into the skin where it kills the bacteria.1
  2. Reduces inflammation: As stated, benzoyl peroxide can reduce inflammation inside acne lesions by killing bacteria whose byproducts bring about inflammation.
  3. Exfoliates the skin: Benzoyl peroxide functions as a peeling agent by drying the skin and helping skin cells flake off. This helps to prevent pores from becoming clogged and leading to acne lesions.
  4. Clears clogged pores: Some chemicals dissolve in water and others dissolve in oil. Benzoyl peroxide dissolves in oil. This is important because skin pores are filled with skin oil, and benzoyl peroxide easily dissolves in skin oil, penetrating into pores where it can then work to kill bacteria and unclog the pore.4

Benzoyl Peroxide Properties

How Effective Is Benzoyl Peroxide at Clearing Acne?

Researchers have performed several studies to determine how effective benzoyl peroxide is at treating acne, all of which show us significant effectiveness of 50% or more. However, since 50% isn't good enough, it is important to use it properly to up its chances to completely clear the skin. When used properly and applied generously (after an initial ramp-up phase) it can completely clear acne.

International Journal of Dermatology

A 1986 study published in the International Journal of Dermatology compared the efficacy of a 2.5%, 5%, and 10% concentration of benzoyl peroxide to treat mild to moderately severe facial acne in 153 acne patients over the course of eight weeks. After eight weeks, the researchers examined how well each of the benzoyl peroxide formulations decreased inflammatory acne lesions, such as papules, pustules, nodules, and cysts. They found that:

- The 2.5% concentration reduced the number of inflammatory acne lesions by 50.9%

- The 5% concentration reduced the number of inflammatory acne lesions by 57.7%

- The 10% concentration reduced the number of inflammatory acne lesions by 44.7%

They also found that the side effects of benzoyl peroxide, which include burning, redness, and skin peeling, are worse after using the 10% concentration than they were after using the 2.5% or 5% concentrations. The study concluded, "[A] lower concentration of benzoyl peroxide should be useful for treating patients with easily irritated skin."5

British Journal of Dermatology

A 1988 study published in the British Journal of Dermatology compared the efficacy of benzoyl peroxide to that of clindamycin phosphate, which is a common topical antibiotic used in the treatment of acne. To perform this study, the researchers divided a group of 60 patients with mild to moderate acne into two groups: one group used benzoyl peroxide, and the other used clindamycin phosphate daily for 4 months. The study found that after 4 weeks of treatment, benzoyl peroxide caused a 66.7% reduction in acne lesions, and clindamycin phosphate caused a 59.1% reduction. However, after 12 weeks of treatment, benzoyl peroxide caused a 59.8% reduction in acne lesions, while clindamycin phosphate only caused a 34.4% reduction. They also found that benzoyl peroxide decreased skin oiliness, and caused skin peeling, while clindamycin phosphate did not impact skin oiliness but caused less skin peeling than benzoyl peroxide.6

Journal of Drugs and Dermatology

A 2009 review published in the Journal of Drugs and Dermatology examined a study that compared the efficacy of 3% benzoyl peroxide to that of 5% benzoyl peroxide combined with an antifungal agent. The researchers found that the 3% benzoyl peroxide treatment reduced the number of acne lesions by 16%, while the combination of 5% benzoyl peroxide and antifungal agent reduced acne lesions by 64%. Therefore, the researchers concluded that the combination of benzoyl peroxide with an antifungal agent may be as effective as combinations of benzoyl peroxide and antibiotics like clindamycin phosphate at treating acne. This is beneficial in acne treatment because an antifungal agent may be better tolerated than antibiotics.7

Journal of Drugs and Dermatology

A 2009 review published in the Journal of Drugs and Dermatology examined a study that compared the efficacy of combining 6% benzoyl peroxide with 0.1% tretinoin, which is a retinoid that is commonly used for the treatment of acne. After 12 weeks of treatment, the researchers found that the combination of tretinoin and benzoyl peroxide cleared acne much better than tretinoin on its own. Therefore, they deemed the combination of benzoyl peroxide and tretinoin effective at treating acne.7

Benzoyl Peroxide Efficacy Studies

Side Effects of Benzoyl Peroxide

The most common side effects associated with benzoyl peroxide are:

  • Redness
  • Dryness
  • Peeling
  • Burning
  • Itching
  • Contact dermatitis (in 1 - 2.25% of people)

These side effects occur within the first few weeks of treatment, and dramatically subside after a few weeks of use.2,4It's important to start slowly, using only a pea-sized amount of benzoyl peroxide and only using it once a day for the first week that you use& benzoyl peroxide to limit these side effects. Then, you can move to twice a day application and slowly ramp up your dosage of benzoyl peroxide so that after 1 month you are using a generous amount of benzoyl peroxide to adequately clear the skin.

Side Effects of Benzoyl Peroxide

Benzoyl Peroxide Can Prevent Antibiotic Resistance

A major benefit of using benzoyl peroxide in the treatment of acne is that bacteria will always die in its presence because benzoyl peroxide does not cause antibiotic resistance. With antibiotics, bacteria can develop resistance, which means that all the bacteria is not killed by the antibiotic and it becomes less effective over time. Benzoyl peroxide does not cause antibiotic resistance. Researchers have found that when benzoyl peroxide is used in combination with the antibiotic, clindamycin phosphate, there is 1600% less resistant bacteria than when clindamycin is used on its own. This means that using benzoyl peroxide with antibiotics helps to protect against the development of bacterial resistance.

Bacteria will always die in the presence of benzoyl peroxide. Bacteria cannot become resistant to benzoyl peroxide.

However, it is controversial to use benzoyl peroxide with antibiotics because benzoyl peroxide is usually far better at treating acne than antibiotics, and it does not come with many of the serious and distressing side effects that antibiotics cause.7,8

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  1. Sagransky, M., Yentzer, B. A. Feldman, S. R. Benzoyl peroxide: a review of its current use in the treatment of acne vulgaris. Expert Opin Pharmacother 10, 2555 (2009). https://www.ncbi.nlm.nih.gov/pubmed/19761357
  2. Cotterill, J. A. Benzoyl peroxide. Acta Derm Venereol 89, 57 - 63 (1980). https://www.ncbi.nlm.nih.gov/pubmed/6162349
  3. Kraus, A. L. et al. Benzoyl peroxide: an integrated human safety assessment for carcinogenicity. Regul Toxicol Pharmacol 21, 87 - 107 (1995). https://www.ncbi.nlm.nih.gov/pubmed/7784640
  4. Dutil, M. Benzoyl peroxide: enhancing antibiotic efficacy in acne management. Skin Ther Lett 15, 5 - 7 (2010). https://www.ncbi.nlm.nih.gov/pubmed/21076800
  5. Mills, O. H. et al. Comparing 2.5%, 5%, and 10% benzoyl peroxide on inflammatory acne vulgaris. Int J Dermatol 25, 664 - 667 (1986). https://www.ncbi.nlm.nih.gov/pubmed/2948929
  6. Swinyer, L. J. et al. A comparative study of benzoyl peroxide and clindamycin phosphate for treating acne vulgaris. Br J Dermatol 119, 615 - 22 (1988). https://www.ncbi.nlm.nih.gov/pubmed/2974719
  7. Fakhouri, T., Yentzer, B. A. & Feldman, S. R. Advancement in benzoyl peroxide-based acne treatment: methods to increase both efficacy and tolerability. J Drugs Dermatol 8, 657 - 661 (2009). https://www.ncbi.nlm.nih.gov/pubmed/19588642
  8. Harper, J. C. Benzoyl peroxide development, pharmacology, formulation and clinical uses in topical fixed-combinations. J Drugs Dermatol 9, 482 - 487 (2010). https://www.ncbi.nlm.nih.gov/pubmed/20480791

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