Sjalbert50 asks…How do sal acid, BP and sulfur work on acne?
The Right Brain responds:
These three active ingredients all work against acne but they all do their job a little differently.
Benzoyl peroxide (BP)
Surprisingly, the exact mechanism of how BP works is unknown. But we do know that it has antibacterial activity against Propionibacterium acnes
Topical sulfur
Applying sulfur to the skin causes it to dry out which allows excess oil and dirt to be removed. This reduces the chances of the pores becoming clogged and leading to a comedone.
Salicylic acid
This acid is a loosens some of the adhesion between skin cells and therefore increases peeling. It is known as a keratolytic agent.
Note: BP and Sulfur are sold in combination so you get antibacterial and skin peeling.
Image credit: http://www.flickr.com/photos/39696534@N04/
References
http://dailymed.nlm.nih.gov/dailymed/archives/fdaDrugInfo.cfm?archiveid=45207
http://www.drugs.com/mtm/sulfur-topical.html#iVUx2RhbmmwyrBHR.99
http://www.drugs.com/mtm/salicylic-acid-topical.html#VH6W35A0kpgosF0F.99
{ 7 comments… read them below or add one }
But… topical sulfur is comedogenic!!!
@Cristiano: Not according to this article: “It has previously been reported that sulfur is comedogenic in the rabbit ear model as well as on the human back (13). However, another study re-examined the comedogenic potential of sulfur (14). This double-blind, randomized study involved the application of test solutions containing 5% sulfur to comedone-free skin of healthy volunteers with or without active acne. These patches were replaced three times per week for six weeks. At the end of the study, it was concluded that there was no trend or correlation between the presence or absence of sulfur in the formulation and appearance of comedones (14).”
Reference: The use of sulfur in dermatology. http://findarticles.com/p/articles/mi_m0PDG/is_4_3/ai_n12417035/
You probably knew this but a big part of how BP works is through oxidative damage. My understanding of chemistry and how oxidation works is not that great, but I remember reading from some papers that oxidation is how BP kills bacteria. Oxidation is also responsible for some of the downsides of BP, such as depletion of vitamin E from sebum.
I also remember reading that in addition to being oxidant BP also loosens dead skin cells and in that way works like salicylic acid.
@Seppo: Thanks for the comment. There seems to be a lot of overlap in the way these ingredients work. And the mechanisms are not fully understood.
According to the Cosmetics Cop:
Sulfur: Antibacterial agent (Source: Applied Microbiology and Biotechnology, October 2001, pages 282–286) that can be a potent skin irritant and sensitizer. Sulfur also has a high pH, which can encourage the growth of bacteria on skin.
BP: Considered the most effective over-the-counter choice for a topical antibacterial agent in the treatment of blemishes (Source: Skin Pharmacology and Applied Skin Physiology, September–October 2000, pages 292–296). The amount of research demonstrating the effectiveness of benzoyl peroxide is exhaustive and conclusive (Source: Journal of the American Academy of Dermatology, November 1999, pages 710–716). Among benzoyl peroxide’s attributes is its ability to penetrate into the hair follicle to reach the bacteria that cause the problem, and then kill them—with a low risk of irritation. It also doesn’t pose the problem of bacterial resistance that some prescription topical antibacterials (antibiotics) do (Source: Dermatology, 1998, volume 196, issue 1, pages 119–125). Current research shows benzoyl peroxide is more effective than some other prescription treatments for acne, such as oral antibiotics or topical antibiotics (Source: Lancet, December 2004, pages 2188–2195).
Benzoyl peroxide solutions range in strength from 2.5% to 10%. It is best to start with lower concentrations because a 2.5% benzoyl peroxide product is much less irritating than a 5% or 10% concentration, and it can be just as effective. The concentration that is required depends entirely on how stubborn the strain of bacteria in your pores happens to be.
Salicylic Acid: Referred to as beta hydroxy acid (BHA), it is a multifunctional ingredient that addresses many of the systemic causes of blemishes (Source: Seminars in Dermatology, December 1990, pages 305–308). For decades dermatologists have been prescribing salicylic acid as an exceedingly effective keratolytic (exfoliant), but it also is an anti-irritant This is because salicylic acid is a derivative of aspirin (both are salicylates—aspirin’s technical name is acetylsalicylic acid), and so it also functions as an anti-inflammatory (Sources: Archives of Internal Medicine, July 2002, pages 1531–1532; Annals of Dermatology and Venereology, January 2002, pages 137–142; Archives of Dermatology, November 2000, pages 1390–1395; and Pain, January 1996, pages 71–82). Another notable aspect of salicylic acid for treating breakouts is that it has antimicrobial properties (Sources: Preservatives for Cosmetics, 1996, by David Steinberg, Allured Publishing; and Health Canada Monograph Category IV, Antiseptic Cleansers, http://www.hc-sc.gc.ca/english/). It is also well documented that salicylic acid can improve skin thickness, barrier functions, and collagen production (Sources: Dermatology, 1999, volume 199, number 1, pages 50–53; and Toxicology and Applied Pharmacology, volume 175, issue 1, pages 76–82). As an exfoliant, in concentrations of 8% to 12%, it is effective in wart-remover medications. In concentrations of 0.5% to 2%, it is far more gentle, and, much like AHAs, can exfoliate the surface of skin. In addition, BHA has the ability to penetrate into the pore (AHAs do not), and thus can exfoliate inside the pore as well as on the surface of the skin, which makes it effective for reducing blemishes, including blackheads and whiteheads.
Why is it that BP can cause such bad reactions on some skin? I usually use salicylic acid, but switched to BP to see if it would work better to treat acne. I ended up with pretty awful redness from the BP.
@Jennifer, BP causes oxidative damage (inflammation in the skin). That’s how it kills bacteria. The problem is that acne-prone skin already has lot of inflammation, and in some cases using BP is like feeding the fire. It’s also been shown to deplete vitamin E levels from the skin. Vitamin E is one of the main antioxidants protecting sebum from oxidation. With lower vitamin E levels sebum (and the skin) is more prone to inflammation and redness.
This doesn’t happen to everybody. For many BP causes little to no symptoms. But it’s not a bad idea to follow it up with a soothing cream, maybe something with vitamin E to replace what’s lost from BP.