Ingredient | The Gentlest Acid Family
PHA (Polyhydroxy Acid)
INCI · Gluconolactone
Related names and forms: Lactobionic Acid · Polyhydroxy Acid. This list does not indicate synonyms or exact ingredient matches.
Polyhydroxy acids (PHAs) represent the larger-molecule, gentlest members of the AHA family. PHA is a class, not a single molecule; the most common forms are Gluconolactone and Lactobionic Acid. This entry considers the class through its most common representative molecule, Gluconolactone (D-glucono-1,5-lactone). Their large molecular weight gives PHAs slower, more superficial penetration and therefore a broad tolerance range in sensitive and rosacea-prone profiles. Their polyhydroxy structure also contributes a mild humectant aspect and an antioxidant-related context. Labels may show Gluconolactone, Lactobionic Acid or Polyhydroxy Acid. The representative molecule Gluconolactone has a verified individual PubChem record (delta-Gluconolactone, CID 7027, C6H10O6). Lactobionic Acid is a separate PHA molecule, not the same as gluconolactone, so the individual CID represents only gluconolactone. Klaris considers PHAs alongside their form (gluconolactone or lactobionic acid), concentration and other acids used with them.
i. Cosmetic Functions
Frequently Discussed Effects
The following headings summarise areas of effect frequently discussed in the literature; visible results in each area require regular use and a suitable formula.
Gentle Surface Turnover
Their large molecular weight suggests a more superficial, gentler effect than AHAs/BHAs.
A Humectant Aspect
Their polyhydroxy structure gives them a mild humectant profile.
Sensitive-Profile Friendly
Offer a broad tolerance range in rosacea-prone and sensitivity-prone skin.
Mechanism
What Happens Within the Skin?
The following points summarise mechanisms from dermocosmetic literature in plain English. Klaris presents them as background information to help readers understand the context, not as medical claims.
Step 1
Gentle Surface Turnover
Their large molecular weight suggests a more superficial, gentler appearance of surface renewal than AHAs/BHAs.
Step 2
Class and Representative Molecule
PHA is a class. This entry considers its most common representative molecule, Gluconolactone. Lactobionic Acid is a separate PHA form.
Step 3
A Humectant Aspect
Their polyhydroxy structure gives them a mild humectant profile, discussed in relation to a more hydrated appearance.
Step 4
Tolerance in Sensitive Profiles
Their large molecular weight offers a broad tolerance range for rosacea-prone and sensitivity-prone profiles. PHAs are studied for increasing sun sensitivity less than AHAs/BHAs.
Step 5
pH and Free Acid
Their effect depends more on pH and the proportion of free acid than on percentage. For PHAs, this provides a more measured context.
ii. Role in the Formula
How Is It Read on a Label?
PHA formulas generally use 4% - 10%. PHAs are positioned as an introductory ingredient in gradual routines, alone or with AHAs/BHAs. Their low-irritation profile also makes them common in daily toner formulas.
A Closer Look · pH, Stability, Synergy
PHA is the acid family most often suggested as a starting point for someone who wants to try acids but has sensitive or rosacea-prone skin. Molecular weight is the reason: PHAs such as Gluconolactone and Lactobionic Acid are larger than AHAs such as glycolic and lactic acids, meaning slower surface penetration and a broader tolerance range. This entry considers the class through its most common representative molecule, Gluconolactone. However, the label "PHA" describes a family: Lactobionic Acid is a separate PHA molecule, not the same as gluconolactone. The individual CID therefore represents only gluconolactone, not the whole class. Their polyhydroxy structure also gives PHAs a mild humectant aspect and an antioxidant-related context not found in AHAs. The literature studies PHAs for increasing sun sensitivity less than AHAs/BHAs; daytime sun protection nevertheless remains a consistent complement to regular acid use. The cosmetic range is generally 4%-10%, and PHAs are positioned as an introductory ingredient in gradual routines, alone or with AHAs/BHAs. When assessing a PHA product, Klaris considers the form (gluconolactone or lactobionic acid), concentration, pH and other acids used alongside it as a whole.
Typical Concentration Range
4% - 10%
Ingredient Family
Acids
iii. Sensitivity Advisory
A Note on Extra Care in Context
Considering sun protection separately can be a consistent choice with regular use, although PHAs are studied for increasing sun sensitivity less than AHAs/BHAs.
A sensitivity advisory is not an instruction for use; where individual health circumstances, pregnancy or known sensitivities are involved, discussing the decision with your doctor may be a more contextual approach.
Common Misconceptions
Frequently Confused Points
Common Belief
PHA is a weak or ineffective version of AHA.
A More Contextual Reading
PHAs are a gentler acid family with larger molecules. Gentle does not mean ineffective. For sensitive and rosacea-prone profiles, this more measured approach is often a more suitable choice.
Common Belief
Gluconolactone and Lactobionic Acid are the same thing.
A More Contextual Reading
Both belong to the PHA family but are different molecules. PHA is a class name, so an individual CID identifies only the representative molecule, gluconolactone, not the whole class.
Common Belief
PHAs do not require sun protection.
A More Contextual Reading
PHAs are studied for increasing sun sensitivity less than AHAs/BHAs, but this does not mean sun protection is unnecessary. Daytime sun protection is a consistent complement to regular acid use.
Common Belief
Sensitive skin can never use products containing acids.
A More Contextual Reading
PHAs stand out precisely in this context: their large molecular weight and broad tolerance range offer an introduction to acids closer to sensitive profiles. Suitability depends on the form, concentration and whole formula.
Scientific Basis
Sources and Their Scope
The following headings indicate areas of research; they are not citations of a specific publication or confirmation that every statement on this page has been verified. The links provided should be read with their individual scope in mind.
- International INCI / CosIng database
- Dermocosmetic research publications
- Literature on sensitive-profile assessment
Source Links
Database records provide ingredient identity and registration information; on their own, they do not establish the effect of a finished product or its suitability for a profile. Search links are not specific research papers.
iv. Related Ingredients
Ingredients Often Read Together
v. Acids Family
Other Ingredients in the Same Family
Explore ingredients in the same functional family to deepen your reading of formulas.
vi. Academy · Related Reading
For a Closer Look
Klaris · Example Analyses
How Does PHA (Polyhydroxy Acid) Feature
in Your Products?
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