PHA: The Third Generation of Exfoliating Acids

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. 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. This is a fundamental difference from most AHAs and BHAs, which can temporarily leave the skin feeling drier or more sensitized afterward.

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. PHA molecules carry multiple hydroxyl (-OH) groups which weaken the bonds between the desmosomes, allowing dead corneocytes to shed more efficiently and naturally.

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.

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 delivers three simultaneous actions:

• Exfoliation — loosens and removes dead skin cells at the stratum corneum
• Hydration — functions as a humectant, drawing moisture into the skin
• Antioxidant protection — neutralizes free radical damage from environmental stressors

The Different Types of PHA in Skincare

• Gluconolactone — the most common and most studied PHA. Used in our PHA Toner and PHA Body Water Cream.
• Lactobionic Acid — ultra-gentle, particularly strong hydrating and barrier-supporting properties.
• Galactose — the least common PHA in commercial skincare. Supports skin cell renewal.

Gentle Exfoliation Without Irritation

The large molecular size of PHA — gluconolactone has a molecular weight of approximately 178 Da compared to glycolic acid's 76 Da — means it simply cannot penetrate to the deeper layers of the skin where irritation is typically triggered. PHA is consistently suitable for first-time acid users because there is no significant adjustment period.

Hydrates As It Exfoliates

Gluconolactone's humectant function actively draws moisture into the skin's surface layers as it exfoliates. Used alongside a dedicated hydrating serum like the Hyaluronic Acid Serum ($23), the combined effect on skin moisture can be significant.

Improves Skin Texture and Tone

Visible changes in skin texture and evenness of tone typically become apparent at the 4–6 week mark with consistent daily or near-daily use. Clinical data from our PHA Body Water Cream confirms brighter, smoother body skin from as early as week 1.

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 for use during pregnancy and breastfeeding.

Anti-Inflammatory and Antioxidant Properties

Gluconolactone has a mild calming effect rather than triggering skin sensitivity. Its antioxidant function neutralizes free radicals generated by UV exposure, pollution, and environmental stressors that accelerate visible aging.

Morning Routine (Face)

1. Cleanse — remove overnight products thoroughly
2. PHA Toner — saturate a cotton pad, sweep over face and neck. Leave on. No rinse.
3. Hyaluronic Acid Serum ($23) — apply to slightly damp skin
4. Eye treatment if using
5. Moisturizer
6. SPF — non-negotiable

Evening Routine (Face)

1. Double cleanse — Oat Cleansing Balm ($17) to remove SPF and makeup, then second cleanse
2. PHA Toner — same method as morning, no rinse required
3. Targeted serums — avoid Retinol or Vitamin C on the same night
4. Moisturizer

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 moisturizer needed
• Always follow with SPF in the morning
• Pre-tan prep: use in the days before applying fake tan for a smooth, even base

INKEY Tip: Do not layer the PHA Toner with other exfoliating acids, Retinol, or Vitamin C in the same routine.

PHA Toner vs Glycolic Acid Toner

PHA Toner ($18): Best for sensitive, dry, or reactive skin. Daily use once adjusted. Hydrates while it exfoliates. Safe during pregnancy and breastfeeding.

Glycolic Acid Toner ($18): Best for skin that tolerates acids well. Contains 10% AHA. Evening use only, 1–3x per week. Not recommended for sensitive skin or during pregnancy.

The clearest decision guide: if glycolic acid has caused redness, stinging, or persistent irritation in the past, PHA is the appropriate next step.

PHA Toner ($18 / 100ml)

Rated 4.5 stars from 344 verified reviews

Key ingredients:

• 3% PHA (Gluconolactone) — gently exfoliates and smooths skin texture at the surface. Formulated at pH 3.62.
• 3% Niacinamide — reduces excess oil production, minimizes pore appearance, evens skin tone.
• Aloe Barbadensis Leaf Juice — naturally soothing and calming.

Suitable for: All skin types, sensitive skin, pregnancy and breastfeeding | Certifications: Vegan, fragrance-free, gluten-free, pregnancy safe

How to use: Apply to a cotton pad and sweep gently over face and neck after cleansing, AM and/or PM. No rinsing required. Build from 2–3 times per week to daily use. Always follow with SPF in the morning.

Shop PHA Toner

PHA Body Water Cream ($15 / 150ml)

Rated 4.5 stars from 271 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 skin barrier & significantly improve & maintain 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), Jojoba, Rice Bran

Suitable for: All skin types, sensitive skin, pregnancy and breastfeeding | Certifications: Vegan, fragrance-free, gluten-free, silicone-free, alcohol-free, clinically tested

How to use: Apply AM and/or PM to clean, dry skin. Massage in until fully absorbed. No rinsing required.

Shop PHA Body Water Cream

Save up to 20% with our Bundle Builder

Potential Side Effects — Rare and Mild

Who Should Exercise Additional Caution

Always patch test. Learn how to patch test correctly.

Application Technique:

Apply PHA Toner to a cotton pad — do not apply directly from the bottle
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, while skin is freshly cleansed
Common Mistakes to Avoid:
Introducing too fast — start at 2–3 times per week and build up
Layering with other exfoliants — PHA works best as your only acid in that routine step
Skipping SPF — any exfoliant increases UV sensitivity
Expecting overnight transformation — most visible improvements appear at the 4–6 week mark
Applying to wet skin — slightly damp is fine, but excess water dilutes the formula

Both PHA products are formulated around gluconolactone at a 3% concentration calibrated for effective, daily-use exfoliation. The PHA Toner is calibrated to pH 3.62 — low enough for effective exfoliation, stable enough for consistent daily use.

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 PHA Body Water Cream 4-week trial (21 participants) confirmed brighter, smoother, and 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

The PHA Toner at $18 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 $15 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 $60.

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.

Shop PHA Toner | Shop PHA Body Water Cream | Build Your PHA Routine