Polyhydroxy Acid — PHA — belongs to the same family as AHAs (Alpha Hydroxy Acids) and BHAs (Beta Hydroxy Acids), but it represents a meaningful evolution in how exfoliating acids are understood and formulated. Where AHAs like glycolic acid and BHAs like salicylic acid have been in mainstream skincare for decades, PHA is the newer, gentler chapter in the acid story — engineered by nature to deliver exfoliation with significantly reduced irritation risk.

The defining characteristic of PHA is its molecular size. PHA molecules are considerably larger than those of AHAs or BHAs. This is not a limitation — it is the mechanism. Because the molecule is larger, it cannot penetrate deeply into the skin. Instead, it works exclusively at the surface of the stratum corneum, the outermost layer of the epidermis.

PHA also behaves as a humectant — meaning it actively attracts and binds moisture into the skin as it exfoliates. With PHA, exfoliation and hydration happen simultaneously, making it one of the most efficient and skin-compatible exfoliants available in skincare science today.

How PHA Works: The Science Behind Gentle Exfoliation

PHA’s exfoliating action works through a well-understood mechanism. The skin’s outer surface is held together by proteins called desmosomes - the biological glue that keeps dead skin cells (corneocytes) in place. Over time, as this process slows with age, sun exposure, or hormonal changes, dead cells accumulate on the skin’s surface, resulting in a dull, uneven, rough texture.

PHA molecules carry multiple hydroxyl (-OH) groups - this is where the “polyhydroxy” in the name comes from. These groups weaken the bonds between the desmosomes, allowing the dead corneocytes to shed more efficiently and naturally. The result is fresher, brighter skin beneath without the mechanical force or aggressive penetration that harsher exfoliants require.

Because PHA does not penetrate beyond the surface layers, it avoids disrupting the deeper epidermis - which is precisely where the stinging, redness, peeling, and barrier compromise associated with stronger acids originates. This is why PHA is described as suitable for daily use in many formulations, and why first-time acid users are often directed toward it as a starting point.

pH matters here too. For exfoliating acids to be effective, they need to be formulated at an acidic pH. Our PHA Toner is formulated at pH 3.62 - precisely calibrated to deliver effective, consistent exfoliation while remaining within a range the skin can tolerate comfortably. If you want to understand how acids work across a wider context, our complete guide to using acids in your skincare routine covers everything from formulation science to layering rules.

Simultaneously with this exfoliation, PHA draws moisture into the surface of the skin. This humectant behaviour is comparable to that of hyaluronic acid - another well-known humectant - though PHA also delivers the additional benefit of exfoliation in the same step. The result is skin that feels more hydrated after use, not less - a sharp contrast to the temporary tightness or dryness some users experience after AHA or BHA products.

Gluconolactone: The Specific PHA in Our Products

The form of PHA used in both our PHA Toner and our PHA Body Water Cream is gluconolactone. It is the most extensively studied PHA in skincare science and the most widely used in professional-grade formulations for good reason.

Gluconolactone delivers three simultaneous actions:

• Exfoliation - loosens and removes dead skin cells at the stratum corneum for smoother, brighter skin
• Hydration - functions as a humectant, drawing moisture into the skin and improving overall hydration levels
• Antioxidant protection - neutralises free radical damage from environmental stressors such as UV exposure and pollution

This triple-action profile makes gluconolactone the most complete and versatile PHA available in formulation. No other PHA type currently delivers all three of these benefits with the same depth of clinical evidence behind it.

The Different Types of PHA in Skincare

PHA is not a single ingredient - it is a category. The three most relevant forms in skincare formulation are:

• Gluconolactone - the most common and most studied PHA. Delivers exfoliation, humectant hydration, and antioxidant protection. Used in our PHA Toner and PHA Body Water Cream. Best documented for sensitive and all skin types.
• Lactobionic Acid - derived from lactose, this PHA is considered ultra-gentle even within the PHA family. Particularly strong hydrating and barrier-supporting properties. Less commonly seen in mass-market skincare but increasingly used in clinical formulations.
• Galactose - the least common PHA in commercial skincare. Supports skin cell renewal and has been studied in conjunction with other PHAs for barrier function improvement.

Of these three, gluconolactone remains the gold standard for effective, science-backed PHA skincare - which is why it is the active PHA across both of our PHA products. For a broader look at how all exfoliating acid types compare, our complete guide to skincare acids is the best starting point.

Gentle Exfoliation Without Irritation

Gluconolactone has a molecular weight of approximately 178 Da compared to glycolic acid's 76 Da — meaning it simply cannot penetrate to the deeper layers of the skin where irritation is typically triggered. PHA delivers smoother texture, brighter skin, and improved tone without the associated risks.

Hydrates As It Exfoliates

Gluconolactone's humectant function actively draws moisture into the skin's surface layers as it exfoliates. Skin typically feels more comfortable, more supple, and better hydrated after use — not tighter, not drier.

Improves Skin Texture and Tone

Improvements in hydration and surface smoothness can be felt within days of first use. Visible changes in texture and tone typically become apparent at the 4–6 week mark. PHA also helps fade post-inflammatory marks and improve overall skin tone over time.

Safe for All Skin Types Including Sensitive and Blemish-Prone

• Sensitive skin — low irritation profile makes PHA the appropriate choice when other acids have caused reactions
• Dry skin — simultaneous humectant action improves rather than worsens dryness
• Oily and combination skin — Niacinamide in our PHA Toner provides added oil control
• Blemish-prone skin — gently unclogs pores without aggravating active blemishes
• Mature skin — supports cell turnover and hydration simultaneously

Both our PHA Toner and PHA Body Water Cream are confirmed safe during pregnancy and breastfeeding.

Anti-Inflammatory and Antioxidant Properties

Gluconolactone has a mild calming, anti-inflammatory effect — relevant for anyone with reactive skin. Its antioxidant function neutralises free radicals generated by UV exposure, pollution, and environmental stressors.

PHA can be used morning or evening — or both. Start with 2–3 times per week and build gradually to daily use.

Morning Routine (PHA Toner)

1. Cleanse
2. Apply PHA Toner — saturate a cotton pad, sweep over face and neck. Leave on, no rinse.
3. Hyaluronic Acid Serum
4. Eye treatment (if using)
5. Moisturiser
6. SPF — non-negotiable

Evening Routine (PHA Toner)

1. Double cleanse — Oat Cleansing Balm, then regular cleanser
2. Apply PHA Toner — same method as morning
3. Targeted serums (not Retinol or Vitamin C on same night)
4. Moisturiser

PHA Body Water Cream

• Apply AM and/or PM to clean, dry skin
• Massage in circular motions until fully absorbed
• No rinsing needed — leave-on formula
• No separate body moisturiser needed
• Pre-tan prep: use consistently in days before fake tan for smooth, even base

PHA vs AHA vs BHA: How the Acids Compare

What You Can Safely Use PHA With

PHA Toner (£13 / 100ml)

Rated 4.4 stars from 332 verified reviews

Key ingredients:

• 3% PHA (Gluconolactone) — gently exfoliates at pH 3.62
• 3% Niacinamide — reduces oil, minimises pores, evens tone
• Aloe Barbadensis Leaf Juice — soothing and calming

Suitable for: All skin types, sensitive skin, pregnancy and breastfeeding
Targets: Uneven texture, uneven tone, dull skin, blemish-prone skin
Certifications: Vegan, fragrance-free, gluten-free, pregnancy safe

Shop PHA Toner

PHA Body Water Cream (£13 / 150ml)

Rated 4.5 stars from 286 verified reviews

Clinical claims (4-week trial, 21 participants):

• Clinically proven to reveal brighter, smoother, more even body skin in just 1 week*
• Clinically proven to strengthen the skin barrier and significantly improve hydration*
• Clinically proven to visibly reduce dry, flaky body skin in just 7 days*
• 97% of users said it was gentle enough for daily use*

Key ingredients:

• 3% PHA (Gluconolactone) — exfoliates and hydrates in one step
• Jojoba — softens, smooths, and hydrates
• Rice Bran — nourishes and evens tone

Suitable for: All skin types, sensitive skin, pregnancy and breastfeeding
Targets: Dry skin, dull skin, rough texture, uneven body tone
Certifications: Vegan, fragrance-free, gluten-free, silicone-free, alcohol-free, clinically tested

Shop PHA Body Water Cream

PHA Side Effects & Precautions

Who Should Exercise Additional Caution

Application Technique:

• Apply PHA Toner to a cotton pad — do not apply directly from bottle to face
• Sweep in gentle, upward motions across face and neck
• No rubbing — the exfoliation is chemical, not mechanical
• Leave on — do not rinse
• Apply before any other serum or treatment

Common Mistakes to Avoid:

• Introducing too fast — begin at 2–3 times per week and build up
• Layering with other exfoliants in the same routine step
• Skipping SPF — any exfoliant increases UV sensitivity
• Expecting overnight transformation — most visible improvements appear at 4–6 weeks
• Applying to soaking wet skin — clean, slightly damp skin is ideal

Climate Considerations:

• Humid environments: PHA works optimally
• Dry climates / air conditioning: Always follow with moisturiser
• High UV environments: SPF is even more critical

Why 3% Gluconolactone?

3% is the concentration at which gluconolactone delivers consistent, clinically meaningful exfoliation while maintaining the low irritation profile that defines PHA. It can be used daily once adjusted, without the barrier disruption risks of stronger acid formulations.

Why pH 3.62?

Exfoliating acids must be formulated at an acidic pH to remain active. pH 3.62 is low enough for effective exfoliation, stable enough for consistent daily use, and well within the range skin can tolerate without compromise.

The Dual-Action Formula Principle:

• PHA Toner: Exfoliation + oil control (3% PHA + 3% Niacinamide)
• PHA Body Water Cream: Exfoliation + hydration (3% PHA + Jojoba + Rice Bran)

Clinical data from the 4-week trial (21 participants) confirmed brighter, smoother, more even body skin from week 1, with significant improvements in barrier function and hydration maintained throughout.

Morning Routine

Evening Routine

Product Combinations That Work:

PHA is not just for those who cannot tolerate stronger acids — it is a genuinely excellent exfoliant for everyone. Whether you are new to acids entirely, switching after irritation from a stronger formula, or looking for an exfoliant gentle enough to use every day, PHA delivers the results without the compromise.

The PHA Toner at £13 is one of the most accessible ways to introduce a clinically supported exfoliant into your daily routine. Pair it with the PHA Body Water Cream at £13 for a complete face-and-body gentle exfoliation routine. Add the Hyaluronic Acid Serum as the hydration follow-up and you have a complete, evidence-backed routine from exfoliation to moisture — all for under £40.

At The INKEY List, the mission has always been the same: real knowledge, effective formulas, accessible pricing. No unnecessary complexity, no inflated costs. Just better skin, for everyone.