What Is Arbutin? Alpha and Beta Difference, Relation to Hydroquinone

Both forms of arbutin consist of the same two parts: a hydroquinone and a glucose. The only difference is the spatial orientation of the bond connecting them. This small detail, named alpha and beta in chemistry, affects which enzymes can break the molecule down and therefore how it behaves in the skin. This page covers its chemistry and regulation; how to use it in your routine and the list of clinical studies are explained in the arbutin and kojic acid article in the guide.

What is the difference between alpha and beta arbutin?

There is no row in the table saying "alpha is stronger", because the answer to this question is not yet known.

What does the "alpha ten times stronger" claim rest on?

How much a molecule slows an enzyme is measured by a value called IC50: the concentration that halves the enzyme's activity, here in millimolar (mM). The smaller the number, the stronger the molecule. Below are results from different laboratories for the same question.

Marketing describes only the first row. The reasons for the difference cited include the enzyme's source and purity, the substance used in the experiment, pH, and hydroquinone mixed into the compound. Since there is no reliable study that directly compares the two forms in human skin, which one is superior remains an open question.

Does arbutin turn into hydroquinone?

This is the real debate, and the sources do not point in the same direction. A comprehensive review dated 2021 writes that most evidence suggests arbutin acts without releasing hydroquinone, but that the question is unresolved. The EU's scientific committee, in its 2023 opinion, attributes the effect of alpha arbutin largely to hydroquinone release. According to the committee, in human skin enzymes and bacteria break down a significant proportion of alpha arbutin, and the hydroquinone produced disappears quickly, probably by binding to cell components.

Why does this matter? Hydroquinone is banned in cosmetics in the EU, with the only exception being 0,02% in professional nail systems. It carries a hazard classification due to suspected carcinogenicity, and in dark skin it has been linked to a dark discolouration called exogenous ochronosis. Since arbutin carries this molecule in its structure, there are three ways it can convert: during storage in the product, with skin bacteria, and under UV in the laboratory.

The committee said in its preliminary opinion that no safe concentration could be determined without this data. After the manufacturer submitted new tape-stripping studies measuring hydroquinone release in volunteers, the final opinion considered the concentrations below, including combined use, safe. The close relative deoxyarbutin is on the EU's list of prohibited substances.

What are the EU limits for arbutin?

• Alpha arbutin: At most 2% in face cream, at most 0,5% in body lotion.
• Beta arbutin: At most 7% in face cream.
• Hydroquinone: Must be kept as low as possible and must not exceed the unavoidable trace level. In the new studies submitted to the committee, the measurement limit was 3 ppm and the detection limit 1 ppm.
• Timeline: Non-compliant products cannot be placed on the market from 1 February 2025, and cannot be sold from 1 November 2025.

These numbers come from the safety calculation. So 7% beta arbutin does not mean three times as strong as 2% alpha arbutin. The 5-7% alpha arbutin used in some studies is also above the EU limit; the same applies to products labelled with that concentration. Because these limits were calculated for face cream and body lotion, applying a face product across a large body area falls outside the calculation.

What should you look for when buying and storing?

• Check which form the label states. Arbutin means beta, not alpha.
• Avoid products whose ingredient list is missing or whose concentration exceeds the EU limit. The type of spot also changes the choice.
• Keep the product in a cool place; do not leave it in a car or a hot bath. Do not make a mixture at home with raw powder; you cannot control pH or stability.
• Test an unfamiliar product for 7-10 days, twice a day, on the inner arm or elbow crease. Stop if redness or itching occurs.
• For both forms there is no light-related phototoxicity finding, but it is the sun that re-triggers the spot. Apply a broad-spectrum sunscreen of at least SPF 30; renew it every 2 hours and after sweating or swimming.
• Do not start a lightening product on your own during pregnancy and breastfeeding; consult your doctor. If the spot is growing, bleeding or changing colour, see a dermatologist.