Natural preservatives in skincare: which are allowed and how well tolerated they really are

NATURAL SKINCARE

Which preservatives are allowed in certified natural skincare?

Natural skincare with the COSMOS label may only use five groups of preservatives: benzoic acid and its salts, benzyl alcohol, dehydroacetic acid and its salts, salicylic acid and its salts, and sorbic acid and its salts. That is what Appendix V of the COSMOS standard, version 4.2 from September 2025, sets out. The small print is telling: these substances are only allowed temporarily and are reviewed at every revision of the standard, with the aim of removing them as soon as compliant alternatives exist. NATRUE keeps its own list covering essentially the same groups of substances. What the various natural skincare certifications check beyond that is a topic of its own. When it comes to preservation, what matters most is what is missing: parabens are not on any of these lists, and neither is the widely used preservative phenoxyethanol. One point matters for everyday shopping: without a certification label, ‘natural skincare’ is not a protected term. A brand without certification may use any preservative from Annex V and still market its products as natural. The only reliable guide is therefore the INCI list on the pack.

Sodium Benzoate, Potassium Sorbate, Sodium Levulinate: what does each one do?

Sodium Benzoate and Potassium Sorbate are genuine preservatives listed in Annex V, whereas Sodium Levulinate is not a preservative in legal terms but an ingredient that supports preservation. Sodium Benzoate is the sodium salt of benzoic acid, Potassium Sorbate the potassium salt of sorbic acid. Both are organic acids, and how well they work depends heavily on the pH of the formula. Sodium Levulinate, the salt of levulinic acid, and Sodium Anisate, the salt of anisic acid, are not listed in Annex V. In legal terms they therefore do not count as preservatives, but in many natural skincare formulas they sit alongside a genuine preservative. A study in Scientific Reports counts anisic acid and glycols such as Pentylene Glycol among the multifunctional ingredients with antimicrobial properties that complement conventional preservatives or partly replace them. Alcohol can also have a preserving effect if the dose is high enough. Why that makes it such a common ingredient in natural skincare is explained in the article on alcohol in skincare.

Incidentally, a preservative appearing in the INCI list does not mean the system actually works. In the same study, 14 products were put through a challenge test with microbes. A combination of 0.084% Sodium Benzoate and 0.079% Potassium Sorbate met neither the criterion for bacteria nor the one for fungi. Dose, pH and formula decide together.

How much preservative is allowed in cosmetics?

The maximum permitted level is set by Annex V of the EU Cosmetics Regulation, separately for each substance and measured in the ready-to-use product. Switzerland adopts this list through its Ordinance on Foodstuffs and Utility Articles, so the same limits apply to products sold here. For benzoic acid, the regulation distinguishes by product type: 2.5% in rinse-off products, 1.7% in oral care products and 0.5% in leave-on products, each calculated as the acid. For a serum or a face cream, the lowest value therefore applies. The table shows the limits for leave-on products, meaning products that stay on the skin. The actual concentration is not stated on any pack; the INCI list only shows the order. That is why preservatives usually appear near the end of the list: they are used in small amounts.

How long a product keeps once opened is a different question from what it is preserved with. That is covered in a separate article on skincare shelf life after opening.

Is Sodium Benzoate safe in skincare?

At the permitted concentration, Sodium Benzoate is unproblematic for the vast majority of people, but it can trigger a contact allergy in a small group. Recent figures come from an analysis in the journal Contact Dermatitis: between 2008 and 2023, a dermatology clinic in Sheffield patch tested a total of 3,198 patients with 5% Sodium Benzoate. Of these, 57, or 1.8 per cent, had an allergic reaction, and in two thirds of these cases it was clinically relevant. To put this in context: the people tested had come to the clinic with suspected contact eczema, so they were not a cross-section of the general population. The authors describe Sodium Benzoate as an important allergen that is tricky to test, because doubtful and irritant reactions were more than three times as common as clearly allergic ones.

What this means for you: if you have no known reaction to benzoates, there is no reason to avoid Sodium Benzoate across the board. If you do, read the INCI list every time. Sodium Benzoate is also on the list in The Duo of serum and cream, openly declared. Whether an individual ingredient is an ‘additive’ you should avoid on principle is discussed in the article on Swiss skincare without additives.

How well tolerated are benzyl alcohol and dehydroacetic acid?

Most people tolerate benzyl alcohol well, but it is considered an underrated contact allergen – which is precisely why the American Contact Dermatitis Society named it Allergen of the Year 2026. The accompanying review in the journal Dermatitis describes how benzyl alcohol can cause allergic contact dermatitis, particularly with prolonged or repeated exposure. Because it is missing from many standard patch test series, it is easily overlooked as the culprit. Benzyl alcohol is also a fragrance component. If it is used for scent rather than as a preservative, it must be listed individually in the ingredient list of leave-on products from as little as 0.001%, instead of disappearing under the catch-all term Parfum. For dehydroacetic acid, the evidence is thinner. The EU limits it to 0.6% and bans it in sprays, but the available data do not allow any reliable conclusion about how often it causes allergies. As with benzoates, the same holds for both substances: no reason for concern if you have no history of reactions, but a clear suspect if your skin keeps reacting to skincare products.

What does ‘nature-identical’ mean for preservatives?

Nature-identical means that a preservative is chemically identical to a substance that also occurs in nature, but is usually made in a laboratory or on an industrial scale. The COSMOS standard is unusually frank about this: the approved preservatives are mostly of petrochemical origin, but all or most of their structure is found in nature. That is why the standard explicitly classes them as non-natural ingredients that are only allowed as an exception. Sorbic acid is named after the rowan berry, benzoic acid after benzoin resin. Even so, there is no berry extract in the product, just the synthetically produced, identical substance. For your skin, the origin makes no difference; the molecule is the same. The underlying question of whether natural is automatically better is covered in the article on natural Swiss cosmetics. For preservation, the sober conclusion is this: a label such as ‘naturally preserved’ tells you little, whereas the INCI list tells you everything.

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