Preservatives in cosmetics: why are they needed and which ones need attention?

What would happen without preservatives?

Bacteria, yeasts and moulds can multiply anywhere there is water and nutrients. Cosmetic products are often exactly that kind of environment: they contain water, oils, plant extracts, sugars and proteins. On top of that, every time the product is used it comes into contact with our hands, the humidity of the bathroom and the air.

A contaminated product may give itself away through signs such as a bad smell, a change in colour or separation; but sometimes it can harbour harmful microbes without any visible change at all. This can create a risk of infection, especially with products applied around the eyes, on damaged skin or in people with weakened immunity. This is why eye infections and product recalls linked to inadequately preserved products have an important place in the history of cosmetics.

For this reason, EU legislation, and the aligned Turkish legislation, require the safety assessment of products placed on the market to include microbiological stability. Preservatives may only be chosen from the substances on the list permitted by law, and used within the maximum limits set.

Common preservatives of low concern

• Phenoxyethanol: One of the most frequently used preservatives today. It is permitted in the EU up to a maximum of 1%; the SCCS concluded that at this limit it is safe for all consumer groups, including children. Irritation or allergy is rarely reported.
• Sodium benzoate and potassium sorbate: Preservatives also used in food that are generally well tolerated. Because they work better at an acidic pH, they are often seen together with citric acid.
• Methylparaben and ethylparaben: Among the most studied preservatives, and considered safe within the permitted limits. We cover this in detail in our parabens: facts and myths guide.
• Benzyl alcohol: Used as a preservative; it is also one of the fragrance allergens that must be declared.
• Ingredients such as ethylhexylglycerin and caprylyl glycol: Supporting ingredients that boost the effect of the preservative; they are also often found in products marketed as “preservative-free”.

Preservatives that need attention: MIT and MCI

Methylisothiazolinone (MIT) and Methylchloroisothiazolinone (MCI) are powerful preservatives that are effective even at very low concentrations. However, they are also strong contact allergens. Their use increased during the period when the move away from parabens accelerated, after which a marked rise in cases of allergic contact dermatitis linked to MIT was observed in Europe.

In response, the EU banned MIT and the MCI/MIT mixture in leave-on products (such as creams, lotions and wet wipes) and restricted them to a very low maximum in rinse-off products (shampoo, shower gel). In our app these substances are rated in a moderate-to-high risk range in the cosmetics category, depending on the type of product.

Someone who has developed an allergy to MIT may also be exposed to it from non-cosmetic sources such as paints, adhesives or cleaning products. If you have been diagnosed with this allergy, it is important to look for Methylisothiazolinone, Methylchloroisothiazolinone and similar isothiazolinone names on labels.

Formaldehyde-releasing preservatives

Some preservatives work by releasing very small amounts of formaldehyde within the product over time. DMDM Hydantoin, Imidazolidinyl Urea, Diazolidinyl Urea and Sodium Hydroxymethylglycinate belong to this group.

Formaldehyde is classified by IARC as carcinogenic to humans (Group 1); however, this classification is based mainly on high exposure through inhalation in occupational settings. The main practical issue in cosmetics is that formaldehyde is a strong skin allergen. EU law requires products that contain formaldehyde-releasing preservatives, and in which the total formaldehyde released in the finished product exceeds 0.001% (10 ppm), to carry the warning “releases formaldehyde” on the label. This threshold was lowered from the previous 0.05% by a 2022 regulation; at the end of the transition period, from 31 July 2026, old stock without the warning can no longer be sold on the EU market either.

People with a formaldehyde allergy should avoid products containing these preservatives. For others, too, steering clear of this group can be a sensible choice when lower-concern alternatives are available; in our app DMDM Hydantoin is rated in a high range.

Ingredients mentioned as preservatives but with a different role

• Triclosan: It has been used more as an antibacterial agent than as a preservative. Because of concerns about antimicrobial resistance and environmental effects, its use has been restricted in many countries, and in the EU the types of products in which it is permitted have been narrowed.
• Disodium EDTA: Not a preservative itself; it binds metal ions, helping preservatives work better and keeping the product stable.
• Alcohol (Alcohol Denat.): Preserves the product when used at high levels, but it can dry the skin.

Are “preservative-free” products really free of preservatives?

The phrase “preservative-free” usually means that none of the substances on the official list of preservatives in the legislation have been used. These products are often protected by other ingredients with a preservative effect (some glycols, plant extracts, high levels of alcohol or glycerin), by special pump packaging or by a very low water content. Water-free oils, balms and powders may genuinely not need a preservative.

These approaches are legitimate; but “preservative-free” does not automatically mean safer. Some essential oils and plant extracts are used for their preservative effect, and these can themselves be allergens. For more on this, see our fragrance allergens guide.

How to assess preservatives on the label

• Preservatives are usually in the middle or at the end of the list, because they are used at very low levels.
• If you have a known allergy, look directly for that substance's INCI name. An allergy can only be diagnosed with a patch test carried out by a dermatologist.
• Be more selective with leave-on products: Because creams and lotions stay on the skin for hours, the choice of preservative matters more than in rinse-off products.
• Respect the period after opening: The open-jar symbol on the pack and the “6M”, “12M” and so on next to it show how many months the product can be used after opening.
• Use jars with clean hands or a spatula: This reduces the load on the preservative system.

As a general rule, a cream containing well-chosen preservatives is safer than a completely preservative-free one. If you notice redness, itching or a rash after using a cosmetic, stop using the product and see a dermatologist.