AHAs and BHAs are both chemical exfoliants — they dissolve the bonds that hold dead skin cells together, accelerating cell turnover and revealing fresher, clearer skin underneath. But they work differently, penetrate differently, and are suited to different skin concerns and types. Understanding which one your skin needs — or whether you need both — is one of the most practical skincare decisions you can make. Here's the complete guide for Australian skin.
What Is a Chemical Exfoliant?
Exfoliation is the process of removing dead skin cells from the surface of the skin. Physical exfoliation does this mechanically — scrubs, brushes, and cloths. Chemical exfoliation does it biochemically — acids that dissolve the intercellular bonds that hold dead cells together, allowing them to shed naturally rather than accumulating.
Chemical exfoliation is generally preferred over physical exfoliation by dermatologists for most skin types. It's more even, more controlled, and significantly less likely to cause micro-tears or irritation from physical friction — particularly important for Australian skin already managing UV-induced sensitivity.
The two main categories of chemical exfoliants used in skincare are Alpha Hydroxy Acids (AHAs) and Beta Hydroxy Acids (BHAs). A third category, PHAs (Polyhydroxy Acids), exists as a gentler alternative and is worth knowing about, but AHAs and BHAs are the workhorses of chemical exfoliation.
What Are AHAs?
Alpha Hydroxy Acids are water-soluble acids derived primarily from natural sources. They work on the skin's surface and the upper layers of the dermis. The most common AHAs in skincare are:
- Glycolic acid: Smallest molecular weight, deepest penetration, most studied, most potent. Derived from sugarcane.
- Lactic acid: Larger molecule than glycolic, gentler, with added humectant properties. Derived from milk or fermented sources.
- Mandelic acid: Large molecule, very gentle, suits sensitive skin and darker skin tones particularly well.
- Malic acid: Often used in combination with other AHAs. Derived from apples.
- Citric acid: From citrus fruits, used more for pH adjustment than primary exfoliation in most formulations.
What Do AHAs Do?
- Dissolve the bonds between dead skin cells on the surface
- Accelerate cell turnover, revealing fresher skin underneath
- Improve skin texture, smoothness and radiance
- Reduce the appearance of fine lines and wrinkles over time
- Fade hyperpigmentation, sunspots, and post-inflammatory marks
- Improve the penetration of other skincare products applied after
Who Are AHAs Best For?
AHAs are most effective for: dry or dehydrated skin (lactic acid in particular has humectant properties), sun-damaged skin, dull or uneven skin tone, fine lines and surface texture concerns, and hyperpigmentation. They work primarily on the skin's surface and are not effective for congestion or blocked pores.
What Are BHAs?
Beta Hydroxy Acids are oil-soluble acids. The primary BHA used in skincare is salicylic acid, derived from willow bark. Being oil-soluble is the key distinction — it allows BHAs to penetrate into the pore lining, which is composed of sebum and oil.
What Do BHAs Do?
- Penetrate into pores and dissolve sebum and congestion from within
- Exfoliate the pore lining, reducing blackheads and whiteheads
- Reduce acne breakouts — salicylic acid is one of the most evidence-backed acne treatments available without prescription
- Minimise the appearance of pores by keeping them clear
- Reduce inflammation — salicylic acid has anti-inflammatory properties alongside its exfoliant action
- Improve overall skin clarity and reduce congestion
Who Are BHAs Best For?
BHAs are most effective for: oily skin, acne-prone skin, congested skin with blackheads or whiteheads, enlarged pores, and combination skin with oily zones. Because they penetrate the pore rather than working on the surface, they address concerns that AHAs simply cannot reach.
AHA vs BHA: The Key Differences
The most practical way to understand the difference is solubility and target:
- AHAs are water-soluble: They work on the skin surface. Target: texture, dullness, fine lines, pigmentation, dry skin.
- BHAs are oil-soluble: They work inside the pore. Target: congestion, blackheads, acne, oily skin, enlarged pores.
If your primary concern is surface texture, radiance and pigmentation — AHA. If your primary concern is congestion, acne and pores — BHA. If you have both concerns — a combined AHA/BHA formulation addresses both simultaneously.
Which Does Australian Skin Need?
Australian skin faces a specific combination of environmental challenges that makes exfoliation particularly important — and the choice between AHA and BHA particularly relevant:
If your main concern is sun damage and pigmentation: AHA. Australia's UV index means cumulative sun damage — hyperpigmentation, uneven tone, rough texture — is one of the most common skin concerns nationally. Glycolic or lactic acid addresses these most directly.
If your main concern is breakouts, congestion and oily skin: BHA. The heat and humidity of Australian summers exacerbates sebum production, leading to more congestion. Salicylic acid inside the pore is the most effective treatment.
If you have both concerns — very common in Australian combination skin: A dual AHA/BHA formulation gives you both surface refinement and pore-clearing in one product, minimising the number of actives you need to manage in your routine.
How to Use AHAs and BHAs Safely
Frequency
Start with two to three times per week and build gradually based on how your skin responds. Daily use is appropriate for some skin types at lower concentrations, but beginning slowly prevents irritation and allows you to find your skin's tolerance point.
When to apply
Chemical exfoliants are best used in the evening. AHAs in particular increase photosensitivity — using them at night allows the acid to work during sleep and gives the skin time to recover before UV exposure the next morning. Always use SPF 30+ the morning after AHA use.
Where in the routine
After cleansing and toning, before serums and moisturiser. Apply to dry skin — wet skin dilutes the acid and reduces efficacy. Wait 60–90 seconds before applying the next product.
Signs you're over-exfoliating
Excessive redness, stinging that persists after application, increased breakouts, skin that feels tight and raw, or a shiny almost plastic-looking texture are all signs of over-exfoliation. If these appear, stop exfoliation for 1–2 weeks and focus on barrier repair with ceramide-rich moisturiser and gentle hydrating serum before reintroducing exfoliation at a lower frequency.
What Concentration Should You Use?
AHAs:
- 5–8%: Gentle, suitable for beginners and sensitive skin
- 10–15%: Effective for texture, pigmentation and anti-ageing
- 20–30%+: Professional-strength peels — not for home use without guidance
BHAs (Salicylic Acid):
- 0.5–1%: Gentle daily-use concentration
- 2%: The standard effective concentration for acne and pore treatment — this is what most clinical studies use
- Above 2%: Prescription territory in some formulations
AHA/BHA Combination Products
Dual AHA/BHA formulations have become increasingly popular because they address both surface exfoliation and pore congestion in a single product. This is particularly effective as an overnight treatment — the acids work during sleep when skin is in its natural renewal cycle and UV exposure is not a factor.
When choosing a combined product, look for the total acid concentration, the pH (effective chemical exfoliation requires a pH below 4), and the supporting ingredients — a good formulation includes soothing or barrier-supporting ingredients alongside the acids to minimise irritation.
The Victoria Limarin AHA/BHA Overnight Peel Serum
The Victoria Limarin AHA/BHA Overnight Peel Serum combines 15% AHA with 2% BHA alongside Raspberry Extract for antioxidant support — formulated specifically as an overnight treatment to refine surface texture and clear congestion simultaneously. Apply 2–3 times per week in the evening after cleansing and toning, before moisturiser.
For the full exfoliation routine: cleanse with the Crystal Purifying Gel Cleanser, tone with The One Toning Elixir Mist, apply the AHA/BHA Serum, follow with The One Hydrating Elixir to seal hydration overnight.
Browse the full Victoria Limarin treatment serum range to build a complete routine for your skin concerns.
Frequently Asked Questions
What is the difference between AHA and BHA?
AHAs (alpha hydroxy acids) are water-soluble and work on the skin surface — best for texture, dullness, pigmentation and fine lines. BHAs (beta hydroxy acids) are oil-soluble and penetrate into pores — best for congestion, blackheads, acne and oily skin. The key difference is where they work: surface versus inside the pore.
Which is better for acne — AHA or BHA?
BHA (salicylic acid) is more effective for acne. Its oil-solubility allows it to penetrate into the pore and dissolve the sebum and dead cells that cause congestion and breakouts. AHAs work on the surface and cannot reach inside the pore where acne originates.
Can I use AHA and BHA together?
Yes. Combined AHA/BHA formulations are effective and well-tolerated for most skin types. They address both surface concerns (texture, pigmentation) and pore concerns (congestion, acne) simultaneously. If using separate products, apply at the same time in the same routine rather than layering them back to back.
Should I use AHA or BHA for pores?
BHA is more effective for pore appearance. Pores appear enlarged when filled with sebum and dead cells — BHA's oil-solubility allows it to penetrate the pore and clear this congestion from the inside. AHAs improve the skin surface around the pore but cannot reach inside it.
How often should I use chemical exfoliants?
Start with two to three times per week in the evening. Increase frequency gradually based on your skin's response. Most skin types do well at three to four times per week. Daily use is appropriate for lower concentrations and tolerant skin types, but over-exfoliation is a common mistake — if your skin feels raw, tight or reactive, reduce frequency immediately.
Do I need to wear SPF after using AHA?
Yes, absolutely — especially in Australia. AHAs increase photosensitivity by removing the surface layer of dead skin cells that provides some UV buffering. Always apply SPF 30+ the morning after AHA use. This is non-negotiable in the Australian UV environment.
What is a PHA and how does it compare to AHA and BHA?
PHAs (polyhydroxy acids) are a newer generation of chemical exfoliant with larger molecular weights than AHAs, meaning they penetrate more slowly and cause less irritation. They provide similar surface exfoliation to AHAs but are better tolerated by sensitive skin and rosacea. If AHAs cause irritation, a PHA formulation is the logical next step to try.
