Acids in Skincare: How to Formulate with AHA, BHA and PHA Safely and Effectively

Let’s stir up some magic in the lab with today’s hot topic: acids in skincare formulation and how to use AHA, BHA and PHA to create high-performing, safe and truly effective cosmetic products.

Acids are some of the most powerful tools you can work with as a formulator. They are also some of the most misunderstood.

For beauty founders and beginner formulators, acids often feel intimidating. Concerns around irritation, pH, compatibility and regulations can make them seem complex. But once you understand how they behave in a formula, they become incredibly precise and versatile ingredients.

In this guide, we are going to break everything down in a way that makes sense so you can confidently formulate exfoliating skincare that performs beautifully and remains compliant.

Why Acids Are Used in Skincare Formulation

Acids are primarily used for exfoliation, but that word alone does not fully capture their impact.

They work by helping to loosen the bonds between dead skin cells on the surface of the skin. This process accelerates cell turnover and reveals fresher, smoother skin underneath.

From a formulation and marketing perspective, this translates into visible benefits such as:

• smoother skin texture
• improved radiance
• reduction in the appearance of fine lines
• clearer-looking pores
• more even skin tone

This is why acids are found in so many product types, including toners, serums, masks and even cleansers.

Understanding the Three Main Families: AHA, BHA and PHA

Not all acids behave the same way. Choosing the right one depends on your target skin concern, your formulation type and your positioning.

AHA (Alpha Hydroxy Acids): Surface Renewal Experts

AHAs are water-soluble acids that work primarily on the surface of the skin.

Common AHAs include glycolic acid, lactic acid and mandelic acid.

Glycolic acid has the smallest molecular size, which allows it to penetrate more easily and deliver stronger exfoliation. Lactic acid is slightly larger and more hydrating, making it more suitable for sensitive or dry skin types. Mandelic acid, with its larger structure, offers gentler exfoliation and is often preferred in beginner-friendly or acne-prone formulations.

AHAs are ideal for targeting:

• dull skin
• uneven tone
• early signs of ageing
• rough texture

BHA (Beta Hydroxy Acids): Oil-Soluble Clarifiers

The most common BHA in skincare is salicylic acid.

Unlike AHAs, BHAs have more oil-affinity but still requiring water-soluble solvents to dissolve. However, their affinity allows them to better penetrate into pores and dissolve excess sebum.

This makes them particularly effective for:

• oily skin
• acne-prone skin
• blackheads and congestion

From a formulation standpoint, BHA systems require careful solubilisation and pH control to remain effective.

PHA (Polyhydroxy Acids): Gentle Multi-Taskers

PHAs, such as gluconolactone and lactobionic acid, are often described as the next generation of exfoliating acids. They have larger molecular structures, which means they penetrate the skin more slowly and are generally less irritating.

PHAs also bring additional benefits, such as hydration support, antioxidant properties, improved skin barrier function. With that perspective, they are excellent for sensitive skin, compromised skin barriers and beginner-friendly formulations. 

pH: The Most Critical Factor in Acid Formulation

If there is one concept you need to master when working with acids, it is pH. The effectiveness of acids depends on how much of the acid is in its “free acid” form, which is directly influenced by pH.

Lower pH means higher activity, but also higher irritation potential. Higher pH means reduced activity, but improved skin tolerance.

This is where formulation becomes a balancing act. For most cosmetic applications:

• AHA products typically sit between pH 3.5 and 4.5
• BHA systems are often effective around pH 3 to 4
• PHAs can work at slightly higher pH levels (up to 5.5) which are more skin-friendly

The key is to design a formula that delivers results while remaining comfortable and safe for the end user.

Formulation Considerations: What You Need to Get Right

Working with acids is not just about adding them into a formula. Several factors must be carefully controlled.

1. Compatibility with Other Ingredients

Acids can interact with other ingredients in ways that affect stability or performance. For example, certain polymers and gelling agents are sensitive to low pH environments. Electrolytes can also impact viscosity and stability, especially in acid-containing gels (Remember our article on electrolytes in skincare).

2. Solubility and Delivery

Water-soluble acids like AHAs are easier to incorporate into aqueous systems. Salicylic acid, however, requires proper solubilisation using solvents or solubilising systems to ensure even distribution and efficacy as poor solubilisation leads to instability and inconsistent performance.

3. Preservation Strategy

Low pH can support preservation, but it does not replace a proper preservative system. You still need to select a compatible preservative, ensure it works within your pH range and test its efficacy in the final formula. 

4. Packaging Considerations

Acid formulations can be sensitive to light and air. Airless packaging is often preferred in order to maintain stability, reduce oxidation and improve product lifespan. That is a general rule of thumb for all cosmetic products, to be honest. 

Sensory Considerations: Making Acids Feel Good on the Skin

One of the biggest challenges with acid formulations is balancing efficacy with user experience. Acid products can feel, sticky, irritating or drying. This is where formulation expertise comes in.

To improve sensory feel, you can:

• include humectants such as glycerin or propanediol
• add soothing agents like panthenol or allantoin
• use film-formers to reduce irritation perception

The goal is to create a product that delivers results without compromising comfort.

Combining Acids: What Works and What to Avoid

Combining acids can enhance performance, but it must be done carefully. AHA and BHA combinations are common in exfoliating treatments, offering both surface and pore-level action. PHA can be added to create a gentler, more balanced formulation.

However, layering too many acids or combining them with other strong actives can increase irritation risk.

Be cautious when combining acids with:

• retinoids
• high levels of vitamin C in its acidic form
• strong exfoliating enzymes

The key is to design synergy, not overload.

Regulatory and Safety Considerations (EU Focus)

In the European Union, acids are regulated under Cosmetic Regulation (EC) No 1223/2009. Certain acids, such as salicylic acid, have specific concentration limits depending on the product type. Please make sure you carefully read supplier information and the regulation of your country to respect dermal limits!

You must also consider:

• target user group
• area of application
• frequency of use

And most importantly, avoid positioning your product as a medical treatment and ensure all claims remain within cosmetic scope.

Final Thoughts: Mastering Acids Is a Competitive Advantage

Formulating with AHA, BHA and PHA opens the door to some of the most effective skincare products on the market.

When done correctly, acids can transform skin appearance while maintaining comfort and safety.

The key is understanding how they work, respecting their chemistry and designing your formula with intention.

Acids are not just functional ingredients. They are also strong marketing drivers.

A glycolic acid toner may position your brand as results-driven. A PHA serum may position it as gentle and barrier-focused. A multi-acid treatment may communicate high performance and expertise.

The way you formulate directly influences how your brand is perceived.

If you are looking to develop acid-based products that are both high-performing and compliant, my lab can support you from concept to final production, ensuring your formulas meet both consumer expectations and regulatory standards.

Here’s to formulas that work and brands that thrive! 

From my lab to yours, 

Rose