AHA/BHA

Hydroxy Acid actives that gently recalibrate skin pH and refine tone, texture and clarity overnight.

Bestseller

#5 The Serum

Skin-refining serum for resilient skin.

30ml

$213.00

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#5 The Refining Cleanser

(Formerly #5 The Cleanser)

Skin-refining cleanser for oily skin types.

100ml 200ml

From $88.00

#5 The GelCrème

Clarifying gel for combination skin types.

50g

$222.00

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15% Off

The Anti-Ageing Trio (Resilient)

Strengthening, Refining and Rejuvenating Set

$589.05 $693.00

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15% Off

The Anti-Ageing Trio (Sensitive)

Strengthening, Refining and Rejuvenating Set

$607.75 $715.00

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Gift with Purchase

The Discovery Travel Kit

A travel-sized Essential Six ritual

$545.00

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Frequently Asked Questions

What are AHAs and BHAs?

AHAs (Alpha Hydroxy Acids) and BHAs (Beta Hydroxy Acids) are a family of skin-refining acids that work to gently dissolve the bonds between dulling surface cells, supporting natural cellular turnover.
AHAs, including Lactic and Glycolic Acid, are water-soluble and work on the skin's surface. BHAs – most notably Salicylic Acid – are oil-soluble and penetrate the pore. Together they form the Hydroxy Acid Complexes of The Refining Collection.

What is the difference between AHAs and BHAs?

AHAs are water-soluble and work primarily on the skin's surface, refining the appearance of texture, uneven tone, and dullness. BHAs are oil-soluble and penetrate deeper into the pore, making them effective for the appearance of congestion and excess sebum. Many RATIONALE formulations combine both for comprehensive skin-refining benefits.

What do Hydroxy Acids do for skin?

Hydroxy Acids support the skin's natural turnover, helping refine the appearance of texture, brighten dullness, address congestion, and maintain skin pH. With consistent use, they reveal a smoother,
more radiant complexion. Within RATIONALE's Refining Collection, they sit alongside Peptides and are paired with skin-comforting ingredients to maintain barrier resilience while delivering visible refinement.

Which RATIONALE formulations contain AHAs and BHAs?

Hydroxy Acids form the foundation of The Refining Collection, with #5 The Refining Serum as the hero formulation. They also feature in #5 The Refining GelCrème and #5 The Refining Cleanser.

Are AHAs and BHAs safe for sensitive skin?

Yes, when introduced gradually. RATIONALE Hydroxy Acid formulations are paired with skin-comforting actives to support
tolerance across skin types. Sensitive skin types are encouraged to begin with two evenings per week and to layer with Nourishing formulations. Always pair Hydroxy Acid use with daily SPF to help support skin protection and recovery.

How often should I use Hydroxy Acid formulations?

We recommend introducing Hydroxy Acid formulations two to three evenings per week, gradually building to nightly use as tolerance develops. Always apply daily SPF the following morning, as Hydroxy
Acids increase the skin's sensitivity to solar and environmental damage. For tailored guidance, consult our Client Services Team or a RATIONALE Skin Therapist.

Can I use AHAs/BHAs with retinol?

Yes. The Refining Collection (Hydroxy Acids and Peptides) and The Rejuvenating Collection (Vitamin A) work in synergy within the PM Ritual. We recommend introducing one active at a time to assess
tolerance, alternating evenings as you build, and always layering with Nourishing formulations to maintain barrier comfort. Daily SPF is essential when using either active.

A complexion that appears smooth, even, and radiant, where pores look refined, texture is consistent, and tone is clear, is the result of skin renewal working as it should. As we age, or in response to congestion, environmental stress, or uneven sebum production, this natural cycle of cellular turnover slows. Dead cells accumulate at the surface, pores appear enlarged, and the skin's inherent luminosity becomes dulled Alpha-Hydroxy Acids and Beta-Hydroxy Acids address these markers of congestion and slowed skin turnover by dissolving the bonds between dead skin cells, allowing the surfaceto be renewed without the friction and abrasion associated with physical exfoliants that can compromise the barrier.

What’s the difference between Alpha and Beta Hydroxy Acids?

AHAs are water-soluble acids, including lactic and glycolic acid, that work at the skin's surface to visibly refine texture and support an even, brighter tone. BHAs, most commonly salicylic acid, are oil-soluble, giving them the ability to penetrate the pore to target excess sebum and address congestion from the inside out.

At RATIONALE, Hydroxy Acids are delivered through a proprietary complex that maintains the skin's natural pH to visibly refine without disruption. They are found in The Refining Collection and take shape in the following products: #5 The Refining Serum is an evening formulation that visibly smooths uneven tone and texture, refines pore appearance, and promotes a more luminous complexion through consistent renewal.

Where congestion and blemishes are an ongoing concern,#5 The Refining Cleanser offers a deep, refreshing cleanse, while nurturing the skin with ceramides and lipids to fortify barrier function. Those prone to an irregular or overproduction of sebum,but still require much needed hydration, #5 The Refining GelCrème is a valuable asset to an evening ritual, delivering visible improvement to clarity and textural concerns while support skin hydration levels without occluding the complexion.

For more personalised guidance and advice, book a consultation or take our Skin Questionnaire.

Skin Questionnaire