If you've ever looked at an IFRA certificate and wondered why it lists a dozen different percentages, this is for you. The number that matters for your product depends on one thing: its IFRA category.
What IFRA is
IFRA — the International Fragrance Association — publishes the Standards that govern the safe use of fragrance ingredients. Where CLP tells you how to label a hazard, IFRA tells you how much of a fragrance you can safely use in the first place. The current rules are set by IFRA's latest Standards (the 51st Amendment at the time of writing).
Why there are categories
The same fragrance is safe at very different levels depending on how a product is used. A lip balm is ingested in tiny amounts; a candle is never applied to skin at all. So IFRA groups finished products into 12 categories by exposure — how much of the fragrance actually reaches a person, and how. Each Standard then sets a maximum usage level per category.
The categories that matter for home fragrance
Almost everything a home-fragrance maker pours or bottles falls into a single category:
- Category 12 — products not intended for direct skin contact, with minimal transfer to skin. That's candles, wax melts, reed diffusers, room sprays, plug-ins and incense.
Because skin contact is minimal, Category 12 limits are generally the most permissive — but "generally" isn't "always". Some ingredients are still capped, or prohibited, in Category 12 for reasons like inhalation or phototoxicity, so you can't assume any oil is unrestricted.
How a usage limit is set
A fragrance oil is a blend of many ingredients, several of which may be IFRA-restricted. For each category, IFRA works out the highest concentration of the whole oil at which every restricted ingredient still stays within its own limit. That single percentage — the maximum usage level — is what your supplier's IFRA Conformity Certificate reports, category by category.
Reading it off your certificate
Find the row for Category 12 (some certificates label it "12", others by its description). The percentage there is the most of that oil you can use in a candle or diffuser and stay compliant. If it says, say, 40%, then a 10% load sits comfortably within the IFRA limit — though you should still check the CLP outcome at that load, which is a separate question.
How Molekule does this for you
Molekule reads your fragrance's IFRA certificate, picks the right category for each product you make, and tells you the maximum load it allows — alongside the CLP label that same load produces. You get both answers at once: how much you can use, and how you'll have to label it. Try it with your own fragrance certificate.