The Ultimate Guide to Alpha Hydroxy Acids (AHAs)

Alpha hydroxy acids (AHAs) are a popular skincare ingredient. These chemical compounds offer a range of benefits from exfoliating the skin’s surface to addressing fine lines, uneven tone, and much more. In this guide to alpha hydroxy acids, we will delve into the science behind their effects, the best practices for incorporating them into your routine, ingredients to use alongside them (and what to avoid), and popular AHA skincare products currency available. Whether you’re a seasoned skincare enthusiast or just beginning your journey, understanding the science and potential of AHAs can help achieve smoother skin.

What are Alpha Hydroxy Acids?

Alpha Hydroxy Acids (AHAs) are a group of chemical compounds that are widely used in skincare. They are known for their exfoliating properties and ability to improve the appearance and texture of the skin.

In contrast, physical exfoliants like facial scrubs depend on abrasive particles to eliminate dead skin cells and uncover smoother skin, potentially causing micro-scratches and surface damage. Alpha hydroxy acids operate by gently loosening and dissolving away these dead cells. This makes alpha hydroxy acids a preferred method of exfoliation compared to physical and abrasive alternatives.

The Benefits of AHAs in Skincare

Alpha hydroxy acids have a significant impact on skincare due to their ability to exfoliate the skin, stimulate collagen production, and improve moisture retention. The benefits of alpha hydroxy acids include:

Exfoliation: AHAs work by loosening the bonds that hold dead skin cells together. This exfoliation process is essential for maintaining healthy skin because it removes the dull and damaged outer layer, revealing fresher, smoother skin underneath.

Collagen Stimulation: AHAs can signal the skin to produce more collagen, reducing visible signs of aging such as fine lines and wrinkles.

Skin Barrier Function: AHAs help maintain the skin barrier by promoting healthier skin cell turnover. This protects the skin from environmental stressors, and prevents transdermal water loss, maintaining optimal hydration levels.

Hyperpigmentation and Sun Damage: AHAs can fade hyperpigmentation and reduce the appearance of sun damage. They work by encouraging the shedding of damaged skin cells and promoting the growth of new, evenly pigmented cells.

Acne Treatment: Certain AHAs are effective in treating acne. They exfoliate the surface of the skin and increase skin cell turnover, reducing and preventing whiteheads and blackheads.

The Difference Between AHAs and BHAs

Alpha hydroxy acids (AHAs) and beta-hydroxy acids (BHAs) are two categories of chemical exfoliant with distinct differences:

Chemical Structure:

AHAs: AHAs are water-soluble acids, which means they dissolve in water. AHAs are known for their ability to exfoliate the skin’s surface and improve texture.

BHAs: BHAs are oil-soluble acids which means they can penetrate and exfoliate within the pores, making them particularly useful for acne-prone and oily skin.

Exfoliation Location:

AHAs: AHAs primarily work on the surface of the skin, removing dead skin cells and improving skin texture. They are often used to address issues like fine lines, dullness, and uneven skin tone.

BHAs: BHAs can penetrate deeper into the skin, making them effective for unclogging pores and treating acne and blackheads. They work well for those with oily or combination skin.

Skin Types:

AHAs: AHAs are generally suitable for most skin types, including normal, dry, and sensitive skin, depending on the type of AHA and concentration.

BHAs: BHAs are particularly suitable for oily, acne-prone, or combination skin types. They are known for their ability to reduce acne and prevent future breakouts.

Types of Alpha Hydroxy Acids in Skincare

Alpha hydroxy acids are a category of chemical exfoliants widely used in skincare. In contrast to BHAs, namely salicylic acid which is a distinct category of its own, AHAs include six chemical exfoliants commonly found in skincare products:

The six most common AHAs found in skincare are:

• Glycolic acid
• Lactic Acid
• Malic Acid
• Mandelic Acid
• Tartaric Acid
• Citric Acid

Each of these AHAs has different properties, and are beneficial for different skin types, as further explained below.

Glycolic Acid

Glycolic acid, a staple in skincare, derives from sugar cane and is one of the most potent AHAs available on the market.

What sets glycolic acid apart is its small molecular size. This allows it to penetrate the skin more deeply and effectively, making it a top choice for individuals with normal to oily skin and those who want a more intense exfoliation.

The benefits of glycolic acid include:

Exfoliation: With its small molecular size, glycolic acid penetrates the skin’s surface, dissolving bonds between dead skin cells. This reveals fresh skin, improving texture and unclogging pores, reducing the risk of acne.

Collagen Production: Glycolic acid stimulates collagen production, diminishing fine lines and wrinkles for a more youthful appearance.

Skin Tone and Texture: It addresses uneven skin tone and texture by fading hyperpigmentation and promoting a smoother complexion.

Enhanced Absorption: Glycolic acid improves the absorption of other skincare products by removing dead skin cells, maximizing their effectiveness.

Lactic Acid

Lactic acid naturally occurs in milk and is derived from the fermentation of lactose. It stands out as a milder yet highly effective alpha hydroxy acid. Lactic acid has a slightly larger molecular size compared to glycolic acid, so it does not penetrate the skin as deeply or quickly. This quality makes it an excellent choice for sensitive skin and those just starting out in the world of AHAs.

Other benefits of lactic acid include:

Gentle Exfoliation and Hydration: Lactic acid offers a unique combination of exfoliation and hydration. It dissolves dead skin cells while retaining moisture, making it ideal for maintaining a robust skin barrier.

Improved Moisture Retention: It enhances the skin’s ability to hold onto moisture, perfect for addressing dryness and achieving a supple complexion.

Softens and Smoothens: Lactic acid gently buffs away rough patches and uneven texture, leaving the skin feeling smooth and soft.

Hyperpigmentation and Age Spots: It addresses uneven skin tone and age spots, leading to a more even and radiant complexion.

Mild Anti-Aging Benefits: By promoting collagen production, lactic acid helps reduce fine lines and wrinkles, contributing to a youthful appearance.

Malic Acid

Malic acid is naturally produced by our bodies and found in fruits like berries, cherries, pears, and, notably, apples. As one of the mildest alpha hydroxy acids, it’s perfect for sensitive skin and those wanting a gentler chemical exfoliation. Despite it’s gentle nature, some benefits of malic acid include:

Exfoliation for Texture: Malic acid, though gentle, improves skin texture by exfoliating the outer layer of dead skin cells.

Enhanced Hydration: As a humectant, malic acid attracts and retains moisture, which is ideal for combating dry or dehydrated skin.

Pairs Well with Other Actives: When combined with AHAs like glycolic acid or lactic acid, malic acid enhances exfoliation, and complements ingredients like vitamin C and hyaluronic acid.

Suitable for All Skin Types: Its gentle nature makes it suitable for all skin types, promoting pH balance, hydration, brightening, preventing breakouts, and addressing signs of aging by encouraging cellular turnover and reducing fine lines.

Mandelic Acid

Derived from bitter almonds, mandelic acid stands out among alpha hydroxy acid. Unlike typical AHAs, mandelic acid is oil-soluble which allows it to penetrate pores effectively, similar to BHAs. Additionally, its larger molecular size is approximately double that of glycolic acid, which results in a slower and gentler exfoliation process and reduces the risk of irritation. This combination of oil solubility and a larger molecule makes mandelic acid a suitable choice for all skin types, particularly sensitive, acne-prone skin. Other benefits of mandelic acid include:

Gentle Exfoliation: Mandelic acid effectively removes dead skin cells without sensitizing the skin, reducing the risk of irritation.

Antimicrobial Support: Mandelic acid boasts antimicrobial properties which can help combat acne-causing bacteria and fungal infections, contributing to clearer skin and reducing breakouts.

Boosted Collagen Production: Thanks to its ability to increase collagen production, mandelic acid works to fade dark spots and discoloration, reduce fine lines, brighten skin tone, and reduce texture.

Tartaric Acid

Tartaric acid, naturally occurring in grapes, may not steal the spotlight among AHAs, but its unique attributes make it a valuable asset in skincare. While it offers milder exfoliation compared to glycolic and lactic acids, it plays a significant role in enhancing skin health. Tartaric acid’s gentle nature makes it suitable for most skin types. Due to its combined antioxidant and exfoliation properties, it’s often used for reducing fine lines and wrinkles, hyperpigmentation, acne, large pores, and dull or uneven skin tone. Tartaric acid is also beneficial for:

Exfoliation for Smoothness: Its mild exfoliating action aids in removing the outermost layer of dead skin cells, unveiling a smoother and more radiant complexion.

Formulation Stability: Tartaric acid enhances the stability of skincare products, ensuring that they maintain their efficacy and quality over time.

Antioxidant Protection: As an antioxidant, tartaric acid fights visible signs of aging caused by free radical damage and environmental stressors.

Citric Acid

Citric acid, naturally found in citrus fruits like lemons and oranges, is a less well known AHA. Versatile and suitable for most skin types, citric acid’s mild nature allows it to be incorporated into various skincare routines without causing excessive irritation. Though it isn’t primarily known for exfoliation like some other AHAs, it offers a unique set of benefits:

Antioxidant Shield: Citric acid, like ascorbic acid (AKA vitamin C), is an antioxidant found in citrus. It protects the skin from free radical damage and environmental stressors.

Radiant Complexion: As an antioxidant, citric acid is ideal for fading dark spots and achieving a more even and luminous skin tone, especially for those with hyperpigmentation concerns.

Texture Refinement: As an AHA, citric acid has the ability to smooth and exfoliate the skin’s surface, reducing lines, texture, and imperfections.

Sebum Regulation: Citric acid is a natural astringent, helping to dry out excess oil and leaving the skin feeling fresh.

pH Level Balance: Citric acid is an excellent pH balancer and is often added to products as a preservative to balance the product’s pH levels.

How to Incorporate AHAs into Your Skincare Routine

Alpha hydroxy acids are a potent category of skincare ingredient. If you’re a newbie to AHAs, it’s always best to start low and slow to allow your skin type to acclimate to the more irritating nature of chemical exfoliants.

Below, you can find some additional tips and tricks for incorporating AHAs into your skincare routine, to minimize the potential side effects and irritation.

Usage Recommendations:

When incorporating AHAs into your skincare routine, it’s advisable to start gradually with both concentration and frequency. Although many AHA products are labeled for daily use, beginning every other day or even weekly can allow your skin to better adjust. As your skin acclimates, you may choose to increase your use and the concentration of AHA.

Daily: AHAs can be used daily but are often better suited for less frequent use in higher concentrations. For daily use, consider lower concentrations or milder AHAs.

Weekly: Weekly use of AHAs can be effective for most individuals. This frequency helps promote skin cell turnover and gradual exfoliation.

Monthly: Stronger AHAs, or those in higher concentrations (such as clinical strength), may be used once a month or less frequently, as they provide a more intensive exfoliation.

Morning vs. Evening Application:

AHAs, like most exfoliants, are better suited for nighttime skincare regimens, because they can potentially make the skin more vulnerable to UV damage. In addition they also complement the natural overnight skin renewal process, and allow for other overnight skincare ingredients to better penetrate the skin.

Morning: While AHAs can be used in the morning, they may increase sun sensitivity, so ensure you apply broad-spectrum sunscreen as the final step in your morning routine.

Evening: Evening application is common for AHAs since they can work overnight to promote skin renewal. They can be applied after cleansing and before moisturizing.

Steps to Apply AHAs:

Alpha hydroxy acids can come in different forms including toners, serums, masks, moisturizers, and other treatments. AHA toners and serums are generally considered stronger and more effective thanks to their prolonged and more direct contact with the skin.

To incorporate alpha hydroxy acids into your skincare routine:

Cleanse: Start with a gentle, pH neutral cleanser to remove dirt and impurities.

Apply AHA Product: Apply your AHA product (serum or toner) to clean, dry skin. Follow the product’s instructions regarding the amount to use.

Wait: Allow the AHA product to absorb for a few minutes before proceeding to the next step.

Moisturize: Apply a moisturizer to help lock in hydration and maintain the skin’s barrier.

Sunscreen: In the morning, always finish with a broad-spectrum sunscreen with SPF 30 or higher.

Potential Side Effects of AHAs and How to Address Them:

Alpha hydroxy acids are a powerful skincare ingredient that can cause side effects if used improperly. Some side effects of AHAs may include:

Irritation: If you experience redness, burning, or excessive dryness, reduce the frequency of AHA use or switch to a lower concentration. Always perform a patch test before using a new AHA product.

Sun Sensitivity: AHAs can increase sun sensitivity. Minimize your sun exposure, especially during peak hours, and always apply sunscreen in the morning and throughout the day.

Dryness or Flaking: If your skin becomes dry and flakey, you may want to incorporate more hydrating and moisturizing products into your daily routine.

Should you find your skin overly dry, irritated, peeling, or tight, it may indicate a compromised skin barrier. Check out our guide on Repairing Your Skin Barrier for effective tips and strategies.

Mixing AHAs with Other Skincare Products

Alpha hydroxy acids are potent, so it’s essential to carefully introduce them into your skincare regimen. Pay attention not only to when and how you use AHAs but also to the other products you combine with them.

As a general guideline, avoid using strong active ingredients or potentially irritating products simultaneously with AHAs. Instead, opt for gentle and hydrating skincare products. If you notice redness, sensitivity, or irritation, reduce the frequency and concentration of both AHAs and other active ingredients.

The Best Ingredients to Use with AHAs

As mentioned, it’s better to focus on gentle, soothing, and hydrating skincare ingredients when using alpha hydroxy acids. When you’re building a skincare routine that includes AHAs, look for products that contain ingredients like:

Hyaluronic Acid: Hyaluronic acid is a humectant with the ability to hold a significant amount of water, helping to keep your skin well-hydrated and plump. When used with AHAs, it can counteract any potential dryness or irritation that may arise from the exfoliating effects of AHAs.

Ceramides: These natural lipids found in the skin’s outermost layer play a crucial role in maintaining the skin’s barrier function and moisture retention. When using AHAs, include ceramide-rich products in your skincare routine to help reinforce the skin’s barrier.

Glycerin: Glycerin is a humectant that attracts and retains moisture in the skin. It works in harmony with AHAs to maintain hydration levels, ensuring your skin remains supple and moisturized.

Centella Asiatica (Cica): Cica is renowned for its soothing and anti-inflammatory properties. It can help alleviate any redness or irritation that might occur when using AHAs. Cica is especially beneficial for individuals with sensitive or easily irritated skin.

Probiotics: Probiotics support the skin’s natural barrier and can help maintain a healthy skin microbiome. When combined with AHAs, they contribute to overall skin health and balance, reducing the risk of irritation.

Green Tea Extract: Green tea is packed with antioxidants that help protect the skin from free radicals and environmental damage. It complements AHAs by providing an extra layer of defense against oxidative stress while soothing the skin.

Betaine: Betaine is a moisturizing and anti-irritant ingredient that can assist in maintaining skin hydration and minimizing any potential discomfort caused by AHAs.

What Skincare Ingredients Should be Alternated with AHAs?

Certain skincare ingredients, while effective for specific skincare concerns, should be used cautiously alongside AHAs. Combining them can increase the risk of skin irritation or diminish their effectiveness due to the acidity of AHAs. To minimize the chance of irritation while still reaping their benefits, consider alternating these ingredients on different days, opt for products designed to incorporate them harmoniously, or integrate them into your morning skincare routine while reserving your AHA treatment to your nightly routine.

Skincare ingredients to be cautious of when using alpha hydroxy acids are:

BHAs: While both AHAs and BHAs can address acne and blemishes, using them together may lead to irritation. It’s recommended to alternate between AHAs and BHAs on different nights or find a product that combines the two together.

Retinol: AHAs and retinol can both improve skin texture and combat signs of aging but may cause irritation when used together. It’s best to use AHAs and retinol on separate nights.

Peptides: The acidity of AHAs can neutralize topical peptides. To avoid this, wait for 30 minutes after applying your AHA treatment before using peptide products, or apply peptides in the morning and AHAs at night.

Niacinamide: Niacinamide and AHAs can both enhance skin texture and brightness, but combining them at the same time may result in skin flushing, redness, or irritation. Alternate nights between niacinamide and AHAs or use niacinamide in the morning.

Vitamin C: Vitamin C and AHAs should not be used simultaneously due to the potential for increased irritation. Vitamin C is most effective in the morning and AHAs in the evening to address hyperpigmentation, fine lines, and achieve brighter skin.

What Absolutely Should Not be Used with AHAs?

There are certain products, skincare ingredients, and treatments that should not be used with AHAs due to the higher risk of irritation and damage to your skin. This includes:

Physical Exfoliants: Using physical exfoliants like scrubs or cleansing brushes along with AHAs can be too abrasive for the skin and lead to over-exfoliation. Choose one method of exfoliation and stick with it.

Products with Drying Alcohols: AHAs can increase the penetration of alcohol into the skin, potentially causing dryness and irritation. Be cautious when using products with drying alcohols alongside AHAs.

Strong Fragrances and Essential Oils: Fragrances and essential oils can be irritating, especially when combined with AHAs. Opt for fragrance-free or hypoallergenic products to reduce the risk of irritation.

In-Clinic Treatments: Avoid stronger in-clinical treatments like microdermabrasion or chemical peels while using AHAs at home. Always tell your skincare professional what products you’re using before clinical treatments.

Prescription Medications: Certain prescription medications, such as Accutane, can make your skin more thin and sensitive, leading to irritation if used with AHAs. Always talk to your doctor about any prescription medication you may be on before starting alpha hydroxy acids.

Tretinoin: Tretinoin, a potent prescription retinoid, can dry and sensitize the skin. It’s best to avoid using AHAs concurrently with tretinoin unless your skin has acclimated to both products.

Recommended AHA Skincare Products

The widespread popularity of alpha hydroxy acids has led to a wide array of skincare products, with various formulations, concentrations, and types of AHAs. These options encompass gentle, mild exfoliants to more potent treatments promising quicker results. Below, you’ll discover a selection of the most favored AHA skincare products on the market, varying in strength, concentration, and formulation, to help you in choosing the best products for your specific skin type and concerns.