PHA vs AHA: What’s the Difference and Which Exfoliant Is Right for You?

Exfoliation is a cornerstone of any effective skincare routine, but with so many acids on the market, it’s easy to feel overwhelmed. Two of the most popular categories—AHAs (alpha hydroxy acids) and PHAs (poly hydroxy acids)—are often mentioned together, yet they offer distinct benefits and suit different skin needs. Understanding the difference between PHA and AHA can help you choose the right exfoliant for glowing, healthy skin without irritation.

While AHAs have been a go-to for decades, PHAs are gaining popularity as a gentler alternative. Both work by dissolving the bonds between dead skin cells, but their molecular size, penetration depth, and suitability for sensitive skin vary significantly. In this guide, we’ll break down what sets them apart, how to use them, and which Typology Paris products can help you achieve a radiant complexion.

What Are AHAs?

AHAs are water-soluble acids derived from natural sources like fruit, milk, and sugar cane. Common examples include glycolic acid, lactic acid, and mandelic acid. They work by dissolving the ‘glue’ that holds dead skin cells to the surface, promoting cell turnover and revealing fresher, smoother skin underneath. AHAs are particularly effective for addressing dullness, fine lines, uneven texture, and hyperpigmentation.

Because AHAs have small molecular structures, they penetrate deeper into the skin. This makes them highly effective but also increases the potential for irritation, especially for those with sensitive or reactive skin. Glycolic acid, the smallest AHA, can cause stinging or redness if used too frequently or at high concentrations. For this reason, AHAs are best suited for normal, combination, or oily skin types that can tolerate stronger exfoliation.

• Common AHAs: glycolic acid, lactic acid, mandelic acid
• Best for: dullness, fine lines, uneven tone, hyperpigmentation
• Caution: may cause irritation on sensitive skin; always use sunscreen

What Are PHAs?

PHAs are a newer generation of chemical exfoliants that share a similar structure to AHAs but with larger molecular sizes. The most common PHA is gluconolactone, followed by lactobionic acid. Because of their larger molecules, PHAs do not penetrate as deeply into the skin, making them much gentler and less likely to cause irritation. They also have humectant properties, meaning they attract moisture to the skin, which is a bonus for dry or dehydrated complexions.

PHAs are ideal for sensitive skin, rosacea, eczema-prone skin, and even post-procedure skin. They provide the same exfoliating and brightening benefits as AHAs but with a much lower risk of stinging or redness. Additionally, PHAs have antioxidant properties that can help protect the skin from environmental damage. For those new to chemical exfoliation or with reactive skin, PHAs are an excellent starting point.

• Common PHAs: gluconolactone, lactobionic acid
• Best for: sensitive, dry, rosacea-prone, or post-procedure skin
• Bonus: humectant and antioxidant properties

PHA vs AHA: Key Differences at a Glance

To help you decide which exfoliant suits your routine, here’s a quick comparison of PHA and AHA based on molecular size, penetration, irritation potential, and best uses.

• Molecular size: AHAs are small (deep penetration); PHAs are large (surface-level penetration)
• Irritation risk: AHAs are higher; PHAs are lower, making them suitable for sensitive skin
• Hydration: PHAs offer humectant benefits; AHAs can sometimes dry out the skin if overused
• Best for: AHAs target fine lines, pigmentation, and texture; PHAs gently exfoliate while soothing and hydrating
• Sun sensitivity: Both increase photosensitivity, so daily SPF is essential

How to Choose the Right Exfoliant for Your Skin Type

If you have oily or combination skin and want to tackle visible signs of aging or hyperpigmentation, an AHA like glycolic or lactic acid can deliver noticeable results. Start with a lower concentration (5-10%) and use it 2-3 times per week to build tolerance. For a gentle introduction, consider a product like the Gel Nettoyant Visage Exfoliant — PHA 5% + Aloe vera, which combines mild exfoliation with soothing aloe.

For dry, sensitive, or reactive skin, PHAs are your best friend. They exfoliate without stripping the skin’s barrier and add hydration. If you’re looking for a multi-benefit product, the Sérum Réparateur Bi-Phase — Complexe NMF 3% + Squalane helps repair the skin barrier while providing gentle hydration—perfect for pairing with a PHA exfoliant. Always patch-test new acids and introduce them slowly into your routine.

• Start with 1-2 times per week, then increase as tolerated
• Never combine AHAs and PHAs in the same routine unless using a formulated product
• Always follow with a moisturizer and broad-spectrum sunscreen

Can You Use Both AHA and PHA in Your Routine?

Yes, but with caution. Because both are chemical exfoliants, using them together in high concentrations can over-exfoliate the skin, leading to redness, peeling, and a compromised barrier. However, some products combine low percentages of both for a balanced effect. Alternatively, you can alternate nights: use an AHA one night and a PHA the next, or use PHA more frequently and reserve AHA for once or twice a week.

If you have resilient skin and want to maximize results, consider a layered approach. For example, use a PHA-based cleanser or toner daily, then apply an AHA serum a few nights a week. Always listen to your skin—if it feels tight or looks irritated, scale back. Remember, gentle exfoliation is more effective than aggressive over-exfoliation in the long run.

• Alternate days: AHA 2-3x/week, PHA up to daily for sensitive skin
• Use a moisturizer with barrier-repairing ingredients like squalane or ceramides
• Stop use if you experience stinging, peeling, or increased breakouts

Whether you choose an AHA for deeper renewal or a PHA for gentle, hydrating exfoliation, the key is to match the acid to your skin’s needs and tolerance. Start slow, use sunscreen daily, and let your skin guide you. For a gentle yet effective introduction to chemical exfoliation, explore the Gel Nettoyant Visage Exfoliant — PHA 5% + Aloe vera and discover how Typology Paris can help you achieve a smoother, brighter complexion with care.