Using the words “exfoliation” and “acne” together normally is followed by comments regarding flare-ups and increased irritation. But when done right, exfoliation is an important part in keeping acne at bay without added breakouts.
Exfoliation is the removal of dead skin cells and an exfoliant is a product or procedure that does just that.
One of the causes of acne is the lining of your skins pores shedding in sheets rather than in small crumbs. This is often happens alongside an over production of sebum (skin oil) which combined with the shedded skin cells stick together to clog a pore opening. A clogged pore is heaven to acne causing bacteria which multiply inside and cause an inflammatory response – queue pimples. By decreasing the occurrence of clogged pores the potential for acne related bacteria to thrive is greatly reduced.
There are hundreds of different types of exfoliants but they all fall into two types, either physical or chemical.
Physical exfoliants buff away dead skin cells through abrasion – for example a scrub, a rough pad or a rotating brush. Physical exfoliants are bad for acne because the friction they rely on can irritate already inflamed skin and lead to more breakouts.
Chemical exfoliants use acids or enzymes that dissolve the “glue” that bonds skin cells together. As they do not rely on friction to remove dead skin cells they are less likely to cause further break outs.
The most common non-prescription chemical exfoliants are alpha hydroxy acids (an AHA, such as glycolic acid) and beta hydroxy acids (salicylic acid, also known as BHA).
Both AHAs and BHAs can penetrate the protective surface layer of the skin (called the stratum corneum). However, because it’s oil soluble, BHA can also penetrate into pores which are clogged with oily cells and sebum. AHA cannot do this so well.
Once inside the pore the BHA frees the dead cells allowing the pore to become unclogged and destroying the ideal growth environment for bad acne causing bacteria.
Not all exfoliants are created equal – the influence of pH on alpha and beta hydroxy acids
There are hundreds of AHA and BHA products on the market but not all of them are effective. The reason is a little bit of chemistry called the pH/pKa ratio.
You’ll need to hold on to your hats here if you’re not technically minded, or jump to the what does all this mean outside of the chemistry lab section below. OK, you’ve been warned…
pH is a measure of a substance’s acidity or alkalinity and is a scale of 0 to 14. pH gives you information about the concentration of H+ ions (hydrogen ions) floating around in something. Low pH means more acidic, high pH means more alkaline. For example Lemon has a pH of 2.3, pure water has a pH of 7.0 and most soaps have a pH of around 9.0.
AHAs and BHAs are acids, which means H+ ions (the things that make acids acidic) can come off them.
For every acid, there’s a measurement called an acid dissociation constant or more simply, a pKa. It is is a quantitative measure of the strength of an acid in solution and tells you whether the acid prefers to be one uncharged thing (also known as the free acid) or it prefers to fall apart into a negatively charged thing and a H+ ion (called a dissociated acid).
The pKas of various AHAs and BHAs are:
Glycolic acid: 3.83
Lactic acid: 3.86
Madelic acid: 3.41
Malic acid: 3.40
Salicylic acid: 2.97
The most important factor determining how a particular acid falls apart is the pH of the solution it’s in. The lower the pH the higher the amount of uncharged free acid .
This is all very important in acne treatment because to pass into the pore and do it’s work, an hydroxy acid needs to be in it’s uncharged, free acid form.
The optimum is to select a pH high enough to avoid skin burns but optimum for pKa – this so happens to be when the pH equals the pKa value.
So what does all this mean outside of the chemistry lab?
Well if for example you have two products of “10% Salicylic acid”; one at pH 3 and one at pH 3.5 the first tube would have 4.83% of free acid while the second tube would only have 2.28% of free acid – the first tube has twice the amount of Salicylic acid that can pass into the pore and unclog it.
Solutions with both an AHA and a BHA inside them (for example lactic acid + salicylic acid) have a problem – the pH can’t be correct for both so either one of the acid’s is less effective or, as commonly happens, both are at the wrong pH and less effective.
So you know, 28 Day Skin Pore Pure Serum contains solely BHA at a pH of 3.0 which is the perfect pH/pKa ratio for skin.
(C) HarJam Innovations Limited 2019. Images courtesy of Sura Shimazaka from Pexels.