The Effectiveness of Retinoids in the Treatment of Acne
30 November 2023 / 8 minutes read /
Acne is a non-life-threatening but complicated dermatological disease in terms of treatment with obvious symptoms, ranging from blackheads to painful pimples that can turn into cysts or nodules over time with the possibility of long‐term scarring.
It is caused by an alteration in the skin's pilosebaceous unit with clogging due to sebum and dead cells buildup, leading to infection and ultimately inflammation.
Many factors are involved in its development, such as hormones (which is why it is common in teenagers), cleansing routine, genetics, and whether or not you use certain medications or products.
Benzoyl peroxide is a topical medication used to treat acne, either alone or with other treatments. It has a promising working mechanism that makes it one of the main ingredients in the therapeutic regimen, with bactericidal to comedolytic roles. Find out how it works, why it is so recommended for acne and its proven efficacy below.
Also known as BPO, benzoyl peroxide is a skin medication widely used to treat acne¹. The discovery of its role in the skin's inflammatory disease dates back to the 1960s, when physician William Pace tested with a not-so-friendly cream on 286 patients with acne vulgaris, resulting in decreased pimples and consequent skin desquamation². Since then, BPO has been extensively studied and recommended for treating such a condition.
Chemically, BPO is a water-insoluble organic peroxide. It is flammable at high temperatures (100ºC), so it is recommended to protect it from heat ². It is also a potent antioxidant used in the bleaching flour industry and edible oils ³.
Benzoyl peroxide is a bactericidal agent, meaning that it kills bacteria, proven to reduce the count of Cutibacterium acnes (formerly Propionibacterium acnes) on acne-prone skin. International medical academies, such as the European Academy of Dermatology and Venereology ⁴ and the American Academy of Dermatology ⁵, list it as one of the main active ingredients in treating acne, which can be used alone or in combination with retinoids or antibiotics, namely, erythromycin and clindamycin.
But to talk about its effectiveness, we should briefly review how a pimple occurs.
Acne, also medically called acne vulgaris, is a disorder involving the pilosebaceous unit of the skin, which mainly affects teenagers but can also persist into adulthood ⁶. Globally, it ranks 8th in overall disease prevalence, with the highest rates reported in Western Europe ⁷.
It is considered an inflammatory disease and requires mainly four key steps to take place ⁸:
So, we can say then that an ideal acne medication is the one that addresses these four steps or at least partially does so.
For research and routine purposes, acne can be classified in terms of increasing severity according to the Investigator's Global Assessment (IGA) ⁹ as follows:
This score is precise, so in addition to determining how severe your acne is, it is also widely used in scientific studies. In fact, it is the one most recommended by practitioners, and its everyday use is easy given how little time-consuming is ¹⁰.
As early mentioned, besides its moderate comedolytic effect, one of benzoyl peroxide's strengths is its action against bacteria, mainly the facial one Cutibacterium acnes. Here are the main ways BPO works once on the skin:
One of the most essential aspects of acne's genesis is bacterial overgrowth leading to infection and inflammation. Once absorbed, BPO is converted to benzoic acid to finally metabolise in the skin. Once there, it releases free-radical oxygen species when it reaches C. acnes, resulting in the oxidation of bacterial proteins and, of course, leading to its death without allowing microbial resistance ¹ ⁵.
Why do the bacteria die? Because it is naturally anaerobic and must live in oxygen-free environments, otherwise it dies. This is called programmed cell death ¹¹.
An example of this is the novel in vitro study in Japan, which shows that BPO has a potent and rapid microbicidal activity against bacteria and fungi, especially C. acnes, which went from 7 CFU/mL to 2.5 CFU/mL in terms of count after a one-hour exposure to a 2 mmol/L BPO ¹².
Get ready. What's coming up is a bit dense, full of studies and results, but valuable scientific evidence.
Its proven efficacy is anecdotal, and since then, many studies have shown similar results in many ways. Since the most vital thing for acne patients is to notice that their pimples actually disappear, we consider the lesion count the most crucial factor in evaluating an active ingredient. The skin's bacterial count is also important since it is the only way to prove that BPO works by killing the C. acnes.
One of the first investigations using 2.5%, 5%, and 10% BPO found that even the lowest dose (2.5%) decreased the pimple count (papules and pustules), providing a 55.90% improvement at week 8 of daily treatment ¹⁴. Individuals who enrolled had at least ten pimples on their faces.
The same study emphasises that the skin count of C. acnes can be reduced from 5.6 to 3.4 CFU after one week of topical application. This bacterial suppression increases as treatment progress.
Another more recent study showed that daily benzoyl peroxide gel, either 2.5% or 5%, for 52 weeks significantly reduced the pimples and comedones count. In fact, it matches the anecdotal study above, giving an improvement rate of 55.7% at week 8 of treatment ¹⁵.
The gold standard is the combined regimen. It has been shown to increase the effects and thus the results, and science has proven it.
A novel study that goes a step further and considers the microscopic skin structures confirms that the BPO+adapalene combination decreases sebaceous secretion and dissolves the outermost layer of the skin (keratolytic effect) at week 6 of treatment ¹⁶. Both drugs complement each other synergistically, which is why combined therapy is so recommended.
Indeed, using two active ingredients can reduce the acne lesions count by up to twice as much ¹⁷. The same is true when used with an antibiotic such as clindamycin, where the combination is superior in reducing acne lesions compared to using one alone ¹⁸.
You can find benzoyl peroxide in lotions, gels, creams, facial cleansers, and soaps. Its dosage ranges from 2.5% to 10% in over-the-counter products. Once applied to the skin, it may cause some degree of irritation, itching, or burning sensation, especially in concentrations higher than 2.5%.
This side effect improves as the treatment progresses and the skin gets used to the product. Meanwhile, you can use cosmeceuticals to relieve the bothersome symptoms, such as moisturizers, gentle cleansers, and redness relief creams.
Its working mechanism is quite convincing, so it is considered one of the main ingredients in treating all forms of acne (mild, moderate, severe). Similar to azelaic acid, the strength of its antibacterial action is that no resistance has been reported, so the germ will always die in its presence.
In short, BPO is an effective acne medication. It not only reduces the pimples and skin lesions count but also inhibits essential steps in their development, such as killing the main character, C. acnes.
If you are struggling with acne, you must undergo a thorough dermatological examination to determine your severity and the treatment you require according to it. Consult your doctor and do not delay treatment. Pimples can worsen and leave scars that are more difficult to treat.