Walk into any UK skincare aisle — or scroll any beauty retailer's ingredient list — and you will find the same handful of names appearing again and again at the bottom of the label. One of those is dehydroacetic acid. It rarely gets top billing, it is not the reason you bought the product, and yet it is one of the reasons the product was still safe to use three months after you opened it.
Here is what it actually does, whether it deserves the scepticism some people bring to preservatives, and where you will find it in the REFORM Skincare range.
What is dehydroacetic acid?
Dehydroacetic acid (often shortened to DHA in formulation circles — not to be confused with dihydroxyacetone, the fake-tanning agent, which shares the abbreviation) is a synthetic organic acid used as a preservative in cosmetics. Its INCI name is dehydroacetic acid, and you will also see it listed as sodium dehydroacetate, the water-soluble salt form, which is what most water-based formulas actually use.
Functionally, it is a broad-spectrum antimicrobial: it inhibits the growth of bacteria, moulds and yeasts. In a water-based product — a serum, a cleanser, a cream — that matters enormously. Water is a hospitable environment, and without an effective preservative, a jar of moisturiser becomes a microbial habitat within weeks of opening. Preservatives like dehydroacetic acid are what stand between a formula and spoilage.
It is worth saying plainly: it has no exfoliating, brightening or anti-ageing role. It is not an active. Its entire job is to keep the product itself stable and safe. In comedogenic terms it is rated zero — it does not clog pores — and it does not interact with the skin's renewal cycle or sebaceous glands.
Is it safe?
In the UK, cosmetic preservatives are governed by the same framework as the rest of the EU-derived regime retained in British law: a substance may only be used as a preservative if it appears on the permitted list, and only within the conditions set for that entry. Dehydroacetic acid and its salts are permitted at a maximum of 0.6% expressed as acid, and are prohibited in aerosol dispensers and sprays — a restriction that exists to avoid inhalation exposure, not because the ingredient is problematic on skin.
The safety picture from the assessment bodies is reassuring. The Cosmetic Ingredient Review Expert Panel and the EU's Scientific Committee on Consumer Safety have both assessed it as safe for topical use at permitted concentrations. Clinical data indicates it is non-irritating and non-sensitising at those levels, and it is generally considered suitable for all skin types, including sensitive skin — though, as with any ingredient, individual reactions are always possible.
It is also worth noting that dehydroacetic acid is biodegradable, and is approved for use in natural and organic-certified formulations under schemes such as COSMOS and Ecocert. That surprises people who assume "preservative" and "natural certification" are mutually exclusive. In practice, gentle organic-acid preservatives of this type are one of the reasons certified natural products can be preserved effectively without the preservatives that certification schemes exclude.
What are the benefits for skin?
This is where it helps to be honest rather than to sell. Dehydroacetic acid does not deliver a visible skin benefit in the way vitamin C or retinol does. Its benefits are indirect but real:
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It keeps your product safe. A preserved formula means no bacterial overgrowth, no fungal contamination, and no risk of applying a spoiled product to broken or compromised skin. That is the single most important thing a skincare product can do for you, and it is entirely invisible.
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It protects the actives you paid for. Vitamin C oxidises. Acids degrade. A formula that spoils is a formula that stops working. Effective preservation is what allows the ingredients doing the visible work to remain stable and effective across the product's shelf life and the weeks after opening.
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It allows for gentler overall preservation systems. Because dehydroacetic acid is effective at low concentrations against both bacteria and fungi, formulators can often rely on it alongside a small number of supporting preservatives rather than building a heavier preservation system. For sensitive skin, that typically means less irritation risk overall — though again, the ingredient itself is not a soothing agent.
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It is well tolerated. Non-irritating, non-sensitising, zero comedogenic rating, and suitable across skin types. For anyone who has reacted to harsher preservative systems in the past, this matters.
The honest summary: dehydroacetic acid is the reason your serum is still a serum and not something else entirely. That is not a marketing claim; it is chemistry.
Dehydroacetic acid in REFORM Skincare products
REFORM Skincare formulates with a preservative system that includes dehydroacetic acid and sodium dehydroacetate across its water-based range. Based on the published ingredient breakdowns, you will find it in:
| Product | Category |
| Glycolic Acid Foaming Cleanser | Exfoliating cleanser |
| Salicylic Acid Foaming Cleanser | Cleanser for oily skin |
| Gentle Hydrating Crème Cleanser | Cleanser for dry skin |
| Repair & Renew Gel | Resurfacing treatment |
| HYAL • Vitamin C + E Serum | Antioxidant serum |
| Retinol 1% Crème | Anti-ageing night cream |
The pattern makes sense: dehydroacetic acid appears in the water-based, leave-on and rinse-off formulas where microbial growth is a genuine risk. You will not find it in the anhydrous or purely oil-based products, because those do not support microbial growth in the same way and do not need it.
A note on label reading: because REFORM publishes full ingredient breakdowns rather than a bare INCI string, dehydroacetic acid is often grouped under a "preservative" or "stability" heading rather than listed at the top with the actives. If you are checking a specific product, look at the preservative section of the breakdown rather than only the headline ingredients. Concentrations will be within the 0.6% regulatory ceiling in every case.
The bottom line
Dehydroacetic acid is a permitted, well-studied, broad-spectrum preservative used at low concentration to keep water-based skincare safe and stable. It will not transform your skin, and no credible formulator would claim it does. What it does is quieter and more important: it ensures the glycolic acid, the vitamin C and the retinol in your routine are still doing their jobs when you get to the bottom of the bottle.
If you have sensitive skin, it is one of the more reassuring preservatives to see on a label — gentle, non-sensitising, biodegradable and accepted even under organic certification standards.
