Here's the ultimate beginner's guide to using acids

If there’s one beauty product that changed my life in 2017, it would be chemical exfoliants! I have acids to thank for helping me get this much closer to my chok chok skin goals. My skin has never been so clear and smooth. Even my husband has gotten hooked on skincare ever since I made him try using acids!

I’ve been preaching the gospel of chemical exfoliation to anyone who’s been willing to listen, and as excited as many have been to finally get into it, there’s always this one hurdle: how do you use acids? So once and for all, let’s finally answer all those questions and get you started!


Should you use AHA or BHA?

The first thing you have to figure out is what type of acid fits your skin’s needs best. In our intro to acids, you’ll learn that there are two main acid categories that are specifically used as chemical exfoliants. Alpha hydroxy acids (AHAs) are primarily responsible for removing the topmost layer of your skin, which is where you experience problems like dullness, hyperpigmentation, and rough texture. Simply put, if you want to get a brighter complexion, lighten dark spots, or smoothen your skin, an AHA is probably what you need. The three most common AHAs used in skincare are:

  • Glycolic acid - often has the strongest and fastest effect; good for wrinkle reduction and brightening skin; best for mature and dry skin types
  • Lactic acid - gentler than glycolic; good for brightening skin; best for sensitive skin
  • Mandelic acid - good for fine lines and acne marks; best for sensitive and acne-prone skin

AHAs to try: CosRX AHA7 Whitehead Power Liquid (7% glycolic acid), In Her Element Glow Job (5% glycolic acid), Pixi Glow Tonic (5% glycolic acid), The Ordinary Lactic Acid 10% + HA 2%, Wishtrend Mandelic Acid 5% Skin Prep Water

The second type is called beta hydroxy acids (BHAs), usually featuring salicylic acid or the gentler betaine salicylate (which is actually salicylic acid combined with betaine). While AHAs are water-soluble, BHAs are oil-soluble so it can penetrate even into clogged pores! That’s why it’s a popular ingredient in acne treatments, as the acid can dissolve the sebum blockage. If you want to prevent pimples or get rid of whiteheads and blackheads, BHAs are the way to go.

BHAs to try: CosRX BHA Blackhead Power Liquid (4% betaine salicylate), CosRX One Step Pimple Clear Pads (1% betaine salicylate), The Ordinary Salicylic Acid 2% Solution

When I first started using acids, I was most inclined to start with AHAs because they have humectant properties, meaning they help hydrate the skin. This obviously appeals most to dry skinned girls like me but it doesn’t mean that those with oily skin can’t use AHAs or vice versa. Rather than choosing an acid based on your skin type, it’s best to evaluate what your skin actually needs. I personally find that my skin responds best when I use both!

Do percentages matter?

Yes. Usually a higher percentage corresponds to a more effective product, and you do need a minimum percentage for it to actually have an exfoliating effect. The minimums are 4% for AHAs, 0.5% for salicylic acid, and 1% for betaine salicylate. Percentages much higher than that often indicate a product that causes skin peeling to occur.

Apart from the percentages, the actual pH of the product matters, too! AHAs are most effective at a pH level of 3 to 4, while BHAs work best at a pH of 3. This why acid toners aren’t particularly effective for chemical exfoliation, as they either don't contain an effective percentage (CosRX AHA/BHA Clarifying Treatment Toner) or have a higher pH than needed (CosRX Natural BHA Skin Returning A-Sol). You can check this thread on Asian Beauty Reddit for the percentage values and pH levels of popular AB acids.


How do you apply acids?

Strictly speaking, this varies from product to product so I’ll focus on products that I’ve personally used. The first and general rule is to start by using a low pH cleanser. Even if you’re not using acids, this is the best kind of cleanser to wash your face with because they don’t strip your skin of its protective barrier. Some PV favorites include the In Her Element Low pH Rose Gel Cleanser, the CosRX Low pH Good Morning Gel Cleanser, and the Human Nature Nourishing Facial Wash. Using a cleanser with a higher pH may lessen or maybe even cancel the effectivity of the acids but if you don’t want to change your wash or aren’t sure about its pH level, you may want to apply a pH adjusting toner before acid use to bring your skin back to a natural and healthy acidic state.

After washing and drying your face, it’s time to apply your acids! I’ve used both CosRX AHA and BHA liquids and I find it best to simply apply them by hand because I feel that cotton pads waste product. For the BHA, I use a pump and a half, and pat it all over my face but you may choose to only it apply it on areas where your pores are clogged or most visible. The AHA is a stronger acid so I only use one pump for my entire face, else my skin turns red from over-exfoliation. I’ve since replaced this with the In Her Element Glow Job because I see more of an improvement in my skin with it. I spread a very thin layer of the cream all over my skin, just applying a tiny amount as I go.

For best effect, the acid has to be left alone on your face for the next 15 to 20 minutes so you’ll have to wait until after that to apply the next step in your skincare. This means it will take a while to get through your whole routine so it may be best to apply acids at night, but really only for that reason. AHAs are known to make your skin extra sensitive to the sun but because the effect actually lasts for as long as a week, it doesn’t really matter whether you apply it in the day or night. You definitely need to wear sunscreen every day while using acids, and if you expect to be outdoors for an extended period of time (like on a beach trip), it may be a good idea to stop using acids a week before exposure.

If you’re trying acids for the first time, it’s best to start with just one acid type and to use it once a week for two weeks so your skin gets used to the chemical exfoliation. You can bring it up to twice a week in the weeks after that. Then if you decide to use another acid (for example, add a BHA to your AHA), follow that same cycle of using the new product once a week first.

How often you apply acids will depend on how your skin responds to it. Some people are able to use both acids at the same time and apply them daily, while a weekly application is enough for others. Our skincare needs differ so pay close attention to what works for your skin. What works for me is to alternate usage of AHA (T-Th) and BHA (M-W-F), plus physical exfoliation with Cure (Sun). The CosRX AHA Liquid’s label also specifically states that it shouldn’t be used with any other exfoliation methods so I recommend following that because over-exfoliation is painful and can ruin the progress you’ve made so far.

What about peeling masks?

Peeling masks are usually very strong AHAs that have such a powerful effect that you can only use them once a week or maybe even once a month! They have to be washed off after the prescribed period because the acids are usually too high to leave on, and they usually give much faster results. The name comes from the peeling effect that skin undergoes after to reveal the brighter, smoother skin layer underneath.

Peeling masks to try: Drunk Elephant TLC Sukari Babyfacial (25% AHA and 2% BHA), The Ordinary AHA 30% + BHA 2% Peeling Solution, Juice Beauty Green Apple Peel Sensitive (malic acid, citric acid, tartaric acid, and glycolic acid)

What are possible negative effects?

Not to scare anyone away but acids are pretty potent ingredients, which is why they are so effective. Even using them correctly can result in bad skin reactions so here’s what you should look out for and how to deal them:

  • Over-exfoliation happens when you’re using acids more than your skin can handle. Maybe you apply too much product or use it too frequently. Common signs are red/inflamed skin, itchiness, stinging or extreme sensitivity, peeling, tiny bumps, and pimples. If you experience at least two of these symptoms, stop using any exfoliants (whether chemical or physical) until your skin heals. Using skincare with centella will soothe redness and speed up healing.

  • Breaking out after using acids? You might be purging because chemical exfoliation increases the rate of skin turnover. It can last for as long as a month while your skin get rids of impurities. If your breakouts are in an area where you usually get pimples, there’s a good chance that it’s just purging and you can just continue to use the product. But if you have acne on new areas and continue to appear over a month, the product may not be compatible to your skin and you should discontinue use.

  • A slight stinging is a common sensation from using AHA products and isn’t necessarily a bad thing. If it feels too uncomfortable though, wash the product off with water.

  • BHAs can have a drying effect on skin so it’s best to layer moisture-replenishing products afterwards. I personally like doing a hydrating toner followed by an essence, a serum, and a moisturizer.

Chemical exfoliation is a great way to level up your skincare game but it’s important to really educate yourself about it before you start. The acids are at a lower pH level than the natural state of skin, so it becomes more prone to irritation. To protect your skin, it’s a good idea to include ceramide-containing skincare into your routine as this helps to repair and strengthen your skin barrier. And of course, wearing sunscreen every day is an absolute must!

I got into acids because I received samples of the CosRX liquids, and I was surprised to see how clear the pores on my nose became with just a single use of the BHA! You may experience the same thing or it may take a little longer but you will definitely see an improvement in your skin. If you still feel scared or intimidated by the thought of acids, there’s nothing like understanding them better to help you overcome your fear and take the plunge. I promise you, it’s worth it.

Sources: Lab Muffin, Dermstore, Fifty Shades of Snail, The Wanderlust Project, Asian Beauty Reddit