Dermatologist’s Best Guide on Polyhydroxy Acid (PHA)

Is PHA (polyhydroxy acid) suitable for all skin types? How does it compare to AHAs and BHAs?

Polyhydroxy acids encompass gluconolactone and lactobionic acids. It has been reported in medical papers as early as 2004 to be effective and better tolerated by sensitive, aging skin.

PHAs works similarly to AHAs by causing the dead skin cells (keratinocytes) to shed at a higher rate, causing reduction in skin irregularities such as uneven pigmentation and texture. In addition, they fulfil the same function of allowing cosmeceutical ingredients such as hyaluronic acid and vitamin C serums to penetrate deeper into the skin.

Is there a possibility of suffering from a chemical burn using skincare products that contain PHA?

PHAs are not as commonly used as AHAs and BHAs, especially as chemical peels in dermatologists’ office setting mainly because the depth of penetration and effectiveness may be less. However, in skincare, the medical literature seems to report that it is a much gentler and moisturising type of chemical exfoliant than the other acids present in skincare, which translates into a much lower risk of skin irritation. In fact, PHAs are large molecules which function as humectants meaning that they trap water under the skin, prevent trans-epidermal water loss and have moisturising properties.

Is there one form of PHA that’s stronger than the others? eg. Lactobionic acid vs Gluconolactone  

Clinical studies to date have grouped the use of gluconolactone and lactobionic acids under PHAs which differ from glycolic acids in the fact that they have a larger molecular structure, penetrate the dermis less and hence is less irritating in addition to having humectant (moisture trapping) properties. I am unaware of any head-to-head study which show whether one form of PHA is stronger than the other.

When should I use PHA? Should I use it in the toner, serum, moisturiser, or cleanser step?

The use of PHAs in skincare has been well-reported to have good exfoliating effects but without the irritation that glycolic (AHA) or salicylic acids (BHA) have. However, I generally do not put in chemical exfoliants in skincare because there is always a risk of skin becoming sensitive after being exposed to it on a daily basis.

There are some studies indicating that compared to glycolic acids which are incorporated in several brands of skincare, those which incorporate PHA are much more suited for people with sensitive, eczema skin. However, I would not prescribe that for my patients with eczema and rosacea in the first place due to the risk of irritation.

What should I be looking out for when I use PHAs?

I would say PHAs seem to be rather novel because it’s a term that hasn’t been used in the recent times but our knowledge of it has stemmed since the 1970s and clinical studies have been done with it since 2004. I think it’s important to prioritise, so the main concern really would be to ask yourself what your skin concern is. If it is anti-aging, then chemical exfoliation itself is not going to give you a miracle result.

Chemical exfoliation can be achieved with glycolic acids, BHAs and in this case PHAs may have the same function but with reduced skin irritation. However, chemical peels alone do not satisfactorily target all skin aging concerns, which lasers in combination with a good cosmeceutical regimen can achieve. It is important to caution that while all anti-aging treatments are aimed at increasing collagen production in the skin, an accredited dermatologist still needs to access the individuals’ problems and side effects before recommending combination treatment.

PHAs should be used in conjunction with cosmeceutical ingredients such as vitamin C as well as phyto which are plant-derived antioxidants that have been proven to fight free radical damage which is the key process in anti-aging. Nevertheless, PHAs are a beneficial form of chemical exfoliation and should be placed in the same category as the use of AHAs and BHAs in chemical peels.

One more thing to add, the clinical results in terms of the depth of skin penetration are likely to be less with PHAs. For patients with other forms of skin concerns, for example acne, they may still find that glycolic acid is much more effective in reducing oil control. If their concern is a medical condition like eczema and rosacea, then certainly I would recommend not using any form of chemical exfoliant at all and rather get treated by a dermatologist.

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