Everything You Need To Know About Using AHAs and BHAs

What’s the difference between glycolic, lactic and salicylic acid? All your questions, answered.

A woman using a pipette to drop serum into her palm for an article on exfoliating skincare acids like AHAs and BHAs, including glycolic, lactic and salicylic acids.

(Photo: iStock)

When used properly, a mild skincare acid—either in the form of alpha-hydroxy acids (AHAs) or beta-hydroxy acids (BHAs)—can work wonders on your skin. The main benefit of AHAs and BHAs is that they exfoliate, breaking down dead skin cells for a clearer, more radiant complexion. But, while acids can give you that covetable glow, using them incorrectly can cause irritation and redness. We asked Brenda Patten, a nurse practitioner at The Beauty Clinic by Shoppers, and Dr. Zaki Taher, a dermatologist and associate professor with the Faculty of Medicine at the University of Alberta to share all there is to know about exfoliating skincare acids.

What are skincare acids—and what are the benefits of using them?

Using skincare products that contain exfoliating acid promotes skin turnover to reveal smoother complexion. There are a few different types of acids available on the market—some target acne, some target dark spots and some work more deeply to target wrinkles and fine lines, says Taher.

AHAs and BHAs specifically work to exfoliate away dead skin cells that can cause dullness and breakouts. Dead skin cells also prevent skin from fully absorbing other skincare products, like serums and creams, and can potentially clog pores, which means incorporating acids into your routine will boost your glow. Acids can also help improve hydration and overall skin texture, says Patten.

What are the different types of acids?

While there are multiple types of skincare acids, there are only a few key ones that are commonly used for exfoliation. The two most famous alpha-hydroxy acids are glycolic and lactic acid, explains Taher. Glycolic and lactic are very similar, but lactic tends to be a bit gentler on the skin, making it a great option for first-timers or sensitive skin types.

Salicylic acid is the most well-known beta-hydroxy acid, and a great pick for congested, acne-prone skin.

What’s the difference between AHAs and BHAs?

“Glycolic and lactic acid (AHAs) break up the dead skin cells on the surface of the skin and help smooth, exfoliate and remove superficial pigment on the outer layer of skin. It can even help with some aspects of acne,” says Taher.

“Salicylic acid is extremely useful for acne prone skin, oily skin with a tendency to become congested and mild acne,” continues Taher. Salicylic acid penetrates deeper in the skin than AHAs to remove build-up, banish blemishes and unclog pores.

Essentially, AHAs exfoliate the surface of the skin to target roughness and uneven texture, while BHAs exfoliate deeper in the pores to fight excess oil.

What is the best way to incorporate an exfoliating skincare acid into my routine?

“Acids should be integrated into your skincare routine slowly, in the form of a cleanser, toner or a serum depending on your concerns,” advises Patten. If you’re interested in trying a concentrated serum or toner that contains active acid ingredients, both Patten and Taher recommend introducing it gradually and using the product only once or twice a week until your skin builds up a tolerance. As your skin builds up this tolerance, an acid may be integrated more often, says Patten.

For AHAs like glycolic and lactic acid, take it slow and use a lower percentage acid (around 5 percent) a few times a week to see how your skin handles it. If you’re new to acids, try pre-soaked toner pads—each holds just the right amount of product, thus preventing excessive application that might irritate the skin. Follow up with your serum, moisturizer and sunscreen. If all goes well, you can slowly increase the frequency of your application, and eventually up the percentage (the maximum allowed in Canada is 30 percent in over-the-counter formulas). Taher says that it takes between two to four weeks to see results, such as a clearer, more radiant skin.

For salicylic acid, concentration typically ranges from 0.5 to 2 percent in products—make a selection depending on what your skin can handle. Patten adds that slowly introducing the ingredient in your routine is particularly important for sensitive skin types, while those with oilier skin can generally tolerate acids better. Still not sure? Ask an expert. “Everyone’s skin reacts and responds differently, so it is best to choose an exfoliating regime with the help of an experienced skincare specialist,” says Patten.

When should I use a skincare acid?

Both AHAs and BHAs can be used day or night. Some products are formulated to be used at night as an overnight peel, while others (often serums) are meant to be used in the morning to gently slough off any dead skin cells. No matter when you use your skincare acid, always wear sunscreen during the day—acids can make your skin more sensitive to sunlight.

Are expensive products necessarily better when it comes to AHAs and BHAs?

According to Patten and Taher, prices can vary widely when it comes to over-the-counter products—and you generally get what you pay for. But it’s impossible to judge the quality of a skincare product on price alone. Some expensive formulas might contain fragrances or additional ingredients that could irritate the skin, while some more affordable items might have harsh formulas that will do the same. Both experts agree that since there is no hard and fast rule, it’s best to begin with a mild product that is within your price range and slowly test it on your skin before proceeding to an increased concentration or more expensive product.

If you have a specific skincare concern you want to target (like dullness or breakouts), Patten suggests chatting with a dermatologist or with an expert at a skincare clinic. “Medical-grade skincare products are designed to address specific concerns, so this may be an interest to you if you feel that your over-the-counter acid isn’t delivering the results you had hoped for.”

What should I do if my skin becomes irritated after using a skincare acid?

“There are a variety of reasons for having a reaction to an acid or any skincare product, including allergy, excessive application or using active ingredients in the wrong combination,” says Patten. If you experience an adverse reaction to an acid, like irritation or redness, Patten and Taher suggest stopping your treatment and seeking advice from a skincare specialist.

One bad experience doesn’t mean you have to swear off acids altogether—try a lower dosage or a different form of acid. “Giving the skin some time to recover is important, but there is no need to be afraid or to shy away from trying something else in the future,” says Taher.

It should be noted that skincare acids should not be used near your eyes—the skin in the area is thinner and tends to be more sensitive.

Can I pair skincare acids with other active ingredients?

While some skin types may be able to handle layering more than one active ingredient at a time, others may experience redness or irritation. Unless you’re experienced with exfoliating acids, Patten advises introducing one new product at a time. If your skin becomes irritated, then it may need to be introduced at a lower frequency or it may not be the right product for you.

If you’re using other active ingredients, like retinol, tread carefully. “Adding an acid may initially cause irritation and redness, and it should not be used with retinol until you skin builds up a tolerance,” says Patten. Once your skin has adjusted to using an acid, you will be able to use exfoliating acids with retinol and other active ingredients, just not at the same time. Instead, try an acid in the morning and a retinol at night, or an acid one night and a retinol-infused product the next.


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