IFRA Category-Based Limits Explained: Leave-on vs Rinse-off Products

The logic can be summed up in a single word: exposure. A product applied to the lips may be ingested; an underarm deodorant contacts thin, sensitive skin; a bar of soap lathers for a few seconds and washes away. IFRA builds its entire framework on exactly these distinctions.

The scientific name for this approach is QRA2 (Quantitative Risk Assessment 2). Just as we say the top note lifts away and the next layer takes the stage when talking about scent, in regulation it is the exposure model that takes centre stage. QRA2 brings together three endpoints — dermal sensitisation, phototoxicity, and systemic toxicity — within a single unified framework.

The QRA2 framework evaluates all three endpoints simultaneously when establishing the upper permitted limit for a substance, and applies the most restrictive one.

An important nuance: QRA2 operates on an aggregate exposure basis. IFRA assumes that a consumer is exposed to the same substance from multiple different products throughout the day; as a result, the permitted share from any single product is reduced.

This is also the point at which the natural-versus-synthetic assumption needs to be challenged. Safety depends not on whether a raw material is natural or synthetic, but on the identity of the molecule and the level at which it is used. Some of the most tightly restricted allergens — Citral, Eugenol, oakmoss — occur at high concentrations in natural essential oils. Natural bergamot is phototoxic and can cause pigmentation on sun-exposed skin. By contrast, certain pure synthetic ingredients such as Iso E Super or Ambroxan are virtually free of allergy concerns. In regulatory terms, "natural = safe" is simply incorrect.

A leave-on product remains on the skin (perfume, moisturiser, deodorant); exposure is prolonged and continuous, so limits tend to be strict. A rinse-off product is washed away (soap, shampoo, shower gel); contact is brief, so the same substance is often permitted at a higher level. This is precisely why IFRA splits Category 7 in two: 7A covers rinsed-off hair products, and 7B covers leave-on hair products.

One point deserves clarity: under the 51st Amendment, reed diffusers are no longer classified under Category 12 (candles) but under 10A, because consumers handle the sticks with their hands and transfer the fragrance to their skin. In other words, real-world consumer behaviour determines the category.

The same amendment introduced limits for phototoxic substances in certain rinse-off categories (7A, 9, 10A) for the first time, and Category 6 is now treated as rinse-off for phototoxicity purposes. These changes illustrate just how much of a living system the categories are.

The practical upshot: if you plan to use the same fragrance oil in both a perfume (Cat. 4) and a soap (Cat. 9), the soap may permit a significantly higher usage rate — but pushing that same rate in a perfume could breach an allergen limit. For more detail, see What Are IFRA Standards and How Do They Affect Your Product?

1. Identify your category first

   Does the product remain on skin or is it rinsed off? Where is it applied? Select the correct category from the 12 available based on these answers. Choosing the wrong category is the most common — and most costly — mistake.

2. Request the IFRA Certificate of Conformity

   Obtain the Certificate of Conformity and the SDS (Safety Data Sheet) from your supplier. The certificate provides a ready-made maximum usage rate for each category.

3. Read the row for your specific category

   The certificate will list different rates such as "Cat. 4: X%, Cat. 9: Y%". The row that applies to you is the one for your product's category — not the highest number on the page.

4. Keep your fragrance oil usage rate below that limit

   The fragrance oil percentage in your formula must not exceed the limit for your category. If it does: reduce the rate, change the raw material, or — where appropriate — move the product to a less restrictive category (e.g. from leave-on to rinse-off).

5. Work in grams; convert ml using density

   Build your formula in grams (g). Bear in mind that the specific gravity of fragrance oils and solvents varies considerably: citrus oils run around 0.84, while heavy resins and some synthetics can exceed 1.10. If you ignore density when converting between ml and g, you will encounter overflow or underfill issues in volumetric bottling.

6. Document and file everything

   Record your calculations, the certificate, and your formula. Amendments change; when a new IFRA version is published, updating your documents is your responsibility.

There is also a safety dimension to consider. High-strength ethanol and room fragrance solvents (DPM, MMB, Dowanol, etc.) are highly flammable — they have low flash points. When working with these materials, avoid static electricity, ensure good ventilation, and wear gloves and eye protection.

Finally, IFRA compliance does not replace national legislation. In Turkey, selling cosmetics or perfumes requires company registration and product notification in the ÜTS (Product Tracking System) before placing them on the market; these are subject to official fees — do not assume that "notification is free." The procedure (notification steps) and the obligations (responsible person/manufacturer duties) are separate matters. For further detail, refer to our articles ÜTS Registration: What You Must Do Before Selling Cosmetic Perfumes and What You Need to Know About Fragrance Oil Trade Under KKDİK; for current procedures and fees, always refer to the official TİTCK source.

The three most common mistakes: choosing the wrong category; counting allergens only from added synthetics (and forgetting those present in natural oils); and accepting generalisations such as "fragrance oil is safe up to 20%." These three errors account for the vast majority of recall and non-compliance risks.