From daily-use formulas like Pixi's Glow Tonic and Glossier's newly launched Solution, to more intense treatments, such as Dr Dennis Gross' Alpha Beta Peel Extra Strength Formula, here at Refinery29 we love an acid and the benefits of using the exfoliating, glow-giving beauty hero are seemingly endless.
Of course, there are a variety of acids out there, meaning it's important to find the type to suit your skin before going in all guns blazing. You may be familiar with AHAs – alpha hydroxy acids – which take the form of glycolic, citric and lactic acid. They're derived from fruit, nuts, milk and sugar but, despite generally breaking down the binder between cells, they all have a host of differences.
"Glycolic acid is good for controlling oil production in skin and good for controlling whitehead (milia) formation," Dr. Justine Hextall, a consultant dermatologist on behalf of The Harley Medical Group, explains. "Citric acid is great for brightening skin and, like retinoic acid, continued use will result in a thicker epidermis. Lactic acid is a favourite as it is antimicrobial, reduces pigmentation, breaks down comedones and helps restore the skin's naturally acidic pH [around 5.5], which is very important for optimal skin barrier function."
The second group of acids, with which you'll perhaps also be acquainted, are the BHAs, or beta hydroxy acids. Of this group, the most used strand is salicylic. "Salicylic acid is especially helpful as it likes oil and is keratolytic (breaks down the keratin that blocks pores and causes bumpy skin and acne lesions)," Hextall states. "As such, it is particularly useful to treat all forms of acne (comedones and pustular acne)."
Now we've got our heads around the acids we're most likely to find in our favourite brands, it's time to meet the third acid group that's gaining favour among beauty fanatics. PHAs – poly hydroxy acids – are especially great for those with sensitive skin. If you've used the aforementioned acid groups before, but found that even occasional use aggravated your skin, then PHAs are for you.
"PHAs are basically a more gentle form of AHAs," Hextall explains. "As the molecules are larger, they can't penetrate as deeply into the skin, so any exfoliant is more gentle. They also have some anti-oxidant and anti-inflammatory effects, which is also great for sensitive skin." Alongside being perfectly suited for those of us with delicate skin, what are the other benefits of PHAs?
Firstly, they're humectant, meaning they can retain moisture – perfect for this season's drying weather. Secondly, they strengthen the skin's barrier function, which lends itself well to those with rosacea or eczema. Finally, they're 'tolerable'. Meaning what? I hear you ask. Well, according to Dr. Hextall, that means that PHAs can be combined with retinoids for an increased anti-ageing effect, without causing any irritation.
So where can we find PHAs? One of our favourite products is cult brand Zelens' PH Bio-Peel Resurfacing Facial Pads. They're pre-soaked, meaning you can pop them in your gym bag or travel kit, and can be used daily. Exuviance Evening Restorative Complex is a rich night cream and contains a nice blend of vitamins and botanicals, and NeoStrata Bionic Face Cream is a nourishing day cream that's perfect for sun-damaged skin.
While there are certainly fewer products containing PHAs available right now, as the acid fast becomes a favourite with beauty buyers, we predict more will follow this year.