Ask a RIFM Scientist: What can 30 years of confirmation testing tell us?


The Research Institute for Fragrance Materials (RIFM) evaluates the safe use of fragrance ingredients, drawing on its database of upwards of 70,000 references that include more than 135,000 human health and environmental studies.

Among these studies, the CNIH (short for “Confirmation of No Induction in Humans”) is one of the most critical for confirming fragrance safety.

CNIHs have been used by RIFM scientists for more than three decades to ethically confirm exposure levels below which skin sensitization is not expected to occur.
(Did you know? Skin sensitization is not the same as skin irritation.)

Maura Lavelle, MS, is part of the team at RIFM that assesses the sensitization potential of fragrance ingredients.

Q: What is a CNIH study, and why is it conducted?

A: When previous skin studies suggest that a fragrance ingredient has the potential to induce skin sensitization, RIFM must confirm the science with an ethical trial in humans.

The CNIH is a confirmatory human patch study that RIFM performs to confirm an already determined safe use level for fragrance ingredients.

Confirmation testing helps to ensure that the ingredient is only ever consumed at a level that will not induce sensitization.

RIFM never performs a CNIH to determine a previously unknown safe use level.

Q: How are CNIH studies designed?

A: RIFM has provided its overall CNIH study protocol to an Institutional Review Board (IRB) for review and approval (an IRB reviews the methods proposed for research to ensure that they are ethical).

Before conducting a CNIH on an ingredient, RIFM first analyzes all of the ingredient’s existing study data to calculate a level well below that at which sensitization may occur. That level becomes the dosage that RIFM uses to test the ingredient in the CNIH.

Q: How common is skin sensitization to fragrance ingredients?

RIFM recently investigated over 30 years of data, specifically looking at the outcomes of 154 CNIH studies involving 16,512 human volunteers.

Over the last 30 years, RIFM found that only 0.12% of all CNIH test participants became sensitized—20 out of 16,512.

More recently, only three out of 9,854 volunteers became sensitized, reducing the percentage to 0.03%.

Q: Why has the percentage of induced allergy gone down so much?

A: The decrease that we are seeing is likely the result of improvements made in safe dose selection. As our understanding of sensitization and safe levels has evolved, we have become much better at predicting a likely safe dose before conducting a CNIH.

The CNIH studies that RIFM has conducted more recently use dosages that are supported by better and more robust data. Thus, these CNIH studies are less likely to induce sensitization.

Q: Will RIFM be sharing these findings?

A: Yes. RIFM recently completed a research paper outlining what we discovered in analyzing the last 30 years of CNIH studies. The CNIH paper is currently being peer-reviewed at a scientific journal. Once the journal has accepted and published the CNIH paper, RIFM will make it available to anyone for free download.