Remember that time I explained the difference between alpha- and beta-hydroxy acids? Probably not, go refresh your mind here.
So salicylic acid is technically not a beta-hydroxy acids. In fact this is what one paper had to say about it: “It is erroneous to claim that salicylic acid is a BHA” and “Although some have termed salicylic acid a
BHA, we do not consider it to be a BHA; for that reason, it is
not included in this discussion.” Academics are pretty harsh, poor salicylic acid.
So why do we call it one?
Because we want things simplified – that’s usually how fake science gets spread but that’s why you have your very own Pocket Alchemist. So salicylic acid is actually supposed to be called an aromatic-hydroxy acid. The aromatic ring (the purple circular shape in the structure below) changes how the OH group behaves and therefore has a different mechanism than real BHAs.
Let’s look at the studies
The main focus of salicylic acid is that it helps people with oily skin. This is mainly because it is oil (lipid) soluble and able to target oil in the pores/hair follicles. This is helpful, otherwise we (the oily skinned people) look like we’ve dunked our faces in glycerin by lunch time. Compared to glycolic and lactic acid, salicylic acid’s purple ring (aromatic ring) is makes it non-polar which is why it is more lipid soluble (oils and lipids are generally also non-polar).
Acne is mainly caused by sebum (oil) and dirt build-up in the pores which is then exacerbated by the acne bacterium, C. acnes. Some of us unlucky ones are predisposed to this and have to work hard to keep it in check. Eurgh, the struggle is real. Salicylic acid can help with the oil control and getting rid of any dead cells which gives the little skin bugs food to feed on.
Scars and fine lines
Salicylic acid also has a similar ability of AHAs in that it can sever the bonds of dead cells in the upper skin layer (stratum corneum) – although using a different mechanism. So it has a chemical exfoliation property, allowing scars and acne to be lessened by increasing the cell renewal of the skin.
Some forms/derivatives (salicylates) are being developed to be used in sunscreens because the aromatic ring I mentioned earlier can convert UV visible light into heat. But these are early stage studies and more research is needed.
Willow bark extract – the natural version
Willow bark extract is sometimes touted as a natural version of salicylic acid. It contains a few different salicylates including salicin which can be broken down in the body to salicylic acid. This, however, does not happen on the skin, so willow bark extract does not exhibit the same functionality as salicylic acid. It has its own properties such as anti-inflammatory activity. Usually products that contain this extract is aimed at soothing irritated or itchy skin, or is an oral product. Historically, this extract was used for pain relief, not surprising since salicylates are closely related to aspirin.
I love salicylic acid and I am always looking for products that contain it to combat my oily skin. Its a firm favourite in my skincare routine – which I’m still building and trying to get right.
Stay tuned for the last ingredient of the HA series: gluconolactone.
- FDA – Beta-hydroxy acids
- Alpha-hydroxyacids and carboxylic acids – Yu et al. in Journal of Cosmetic Dermatology
- Clinical and cosmeceutical uses of hydroxyacids – Green et al. in Clinics in Dermatology
- Salicylic acid as a peeling agent: a comprehensive review – Arif in Clinical, Cosmetic and Investigational Dermatology
- Applications of hydroxy acids: classification, mechanisms, and photoactivity – Kornhauser et al. in Clinical, Cosmetic and Investigational Dermatology
- Sunscreen studies:
- Willow bark: