Lab notes > Ingredients > Our guide to understanding exfoliating acids in skincare

Our guide to understanding exfoliating acids in skincare

Here we explore how different acids work to exfoliate the skin, and which is best for each skin type

At Renude, we love incorporating acid exfoliators in our members skincare routines for their amazing skin benefits, but we understand it can be a bit of a minefield navigating the best option for you. After all, there are many different types of acids, and it can be tricky to figure out which will work best for your skin type.

So we’ve written this guide to tell you everything you need to know about exfoliation and the use of acids in skincare. 

What are the benefits of skin exfoliation?

With your skin being under constant physical, chemical and microbial assaults, exfoliation can help to fully remove damaged and dead skin cells from the surface of your skin. Exfoliation is key in sloughing off superficial skin cells (aka. corneocytes) to give way for new and healthy skin cells that are more even in texture, appear brighter, and improve the absorption of other active ingredients in your skincare.

What is the difference between chemical vs physical exfoliation?

Physical exfoliation

Physical exfoliating uses an applied mechanical force and textured cleansing formulation to remove skin cells from the surface of your skin. They are typically abrasives, such as ground nuts, seeds or cellulose beads, which function to increase the mechanical action of scrubbing to dislodge and carry away debris. 

Chemical exfoliation

This involves the use of acids to break the chemical bonds between surface skin cells, allowing them to fall away from the skin to reveal a smoother and brighter surface. These acids are small molecules, able to penetrate the dermis and function at a deeper level to stimulate collagen and target concerns such as acne, scarring and pigmentation.

At Renude, we typically recommend chemical exfoliators in most cases, as they tend to provide a more even and gentle exfoliation, as well as being a more effective treatment choice for a wider range of skin goals. 

AHA, BHA, PHA - what does it mean?

AHAs, BHAs and PHAs are three different categories of exfoliating acids that each resurface the skin but have slightly different solubility profiles and molecular sizes. The smaller the molecular size, the more immediate the effects, but this can also mean more potential side effects (dryness, irritation).

Alpha hydroxy acids (AHAs) are water soluble acids that break down the substance which bonds dead skin cells together. Dissolving these bonds allows for superficial skin cells to be peeled off in layers, providing a similar action as chemical peels. AHAs are derived from natural sources like fruit and grains and examples include citric acid, glycolic acid, lactic acid, mandelic acid, and malic acid, with glycolic having the smallest molecular size. 

See a selection of our favourite AHA exfoliating treatments here

Beta hydroxy acids (BHAs) are oil soluble acids which have the ability to penetrate oil-clogged pores, imparting their anti-inflammatory and antibacterial activity to remove dirt and debris from them. The main BHA used in skincare is salicylic acid, which is derived from willow bark (and is structurally very similar to the painkiller aspirin!)

See a selection of our favourite BHA exfoliating treatments here. 

Polyhydroxy acids (PHAs) function similarly to AHAs but are known to be gentler as these molecules are larger and do not penetrate the skin as deeply. Examples of PHAs are gluconolactone, galactose and lactobionic acid. 

See a selection of our favourite PHA exfoliating treatments here.

Who should be using acids in their skincare?

Acids can work for all skin types, but the best acid for you depends on your skin type and sensitivity. AHAs can be used on any skin type but are best for normal or dry skin as they are water soluble and improve moisturization of the skin. For oily, acne prone or combination skin BHAs are ideal. For very sensitive skin, PHAs are a great option. 

Can people with sensitive skin use acids in skincare?

People with sensitive skin should start with the use of larger acid molecules, such as PHAs or the AHAs lactic acid and mandelic acid, as they are less able to penetrate deeper into the skin, helping to avoid irritation. 

How do you use acids in skincare?

It is important to remember that exfoliation, as everything in life, is best in moderation! The frequency of usage depends on the type of formulation used, as masks and peels may be used once or twice a week, but toners are more likely to be used daily or every other day. Always conduct a patch test to ensure adverse reactions are avoided.

We usually recommend using acids at night as this is when skin is in renewal mode, so it’s ability to generate new skin cells is at its peak. Acids can also increase skin’s sensitivity to sunlight, and so it is important to apply a broad-spectrum sunscreen every morning following chemical exfoliation as well as practising sun safety guidelines. 

Acids should be incorporated into your routine slowly to build up tolerance. We would recommend starting 1-2x week and building up to every other night over a period of a few weeks (or daily if your skin is tolerant).

Retinoids and other potentially irritating active ingredients should not be used in combination, so consider using these on alternate evenings if you’re looking to incorporate both into your skincare routine.

If skin becomes irritated, discontinue use of acids completely until skin sensitivity decreases. While irritation persists, this could be a sign of a damaged skin barrier, so treat skin with gentle cleansers and emollient moisturizers only until skin is healed. 

How long should it take to see results with acids?

As with most things in life, results with acids take time. You may feel your skin to be instantaneously smooth after one use, but deeper concerns such as scarring and textural irregularities, require more time to see an improvement. It takes the outer layer of skin (aka the epidermis) around 4-6 weeks to renew itself completely, so as a guide you should start to see longer term results after 2-3 skin cycles (around 3-4 months). 

Which exfoliating products can help me acheive my skin goals?


If you're wondering if your skin might benefit from adding an acid into your routine, you can sign up to Renude to connect with a licensed expert and receive a personalised skincare routine to suit your unique needs.
 

Samita Verma
Samita Verma
Cosmetic Scientist