Ask a RIFM Scientist

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What is a CNIH, and how does it help assess skin sensitization?

Maura Lavelle, MS

The “Confirmation of No Induction in Humans,” or CNIH, is a human patch study that confirms an already determined safe use level for fragrance ingredients. The CNIH is one of the most critical skin tests for evaluating the safe use of fragrance ingredients. It has been used by RIFM scientists for more than three decades to ethically confirm the absence of skin sensitization at an exposure level based on all existing data.

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. RIFM verifies the science via the CNIH. Confirmation testing helps to ensure that our exposure to the ingredient is at a level that will not induce skin sensitization.

It is important to note that RIFM never performs a CNIH to determine a previously unknown safe use level. Instead, before conducting the CNIH, RIFM first analyzes all of the ingredient’s existing study data to calculate a level well below that at which sensitization may occur.

We recently investigated over 30 years of data from 154 CNIHs involving 16,512 human volunteers. RIFM found that only 0.12% of all volunteers became sensitized (20 out of 16,512). In more recent studies supported by better and more robust data, only 0.03% of volunteers (3 out of 9,854) became sensitized. RIFM summarized these findings in a recent peer-reviewed publication in the journal Dermatitis.

Scientist Maura Lavelle, MS, supports the Skin Sensitization endpoint for RIFM’s safety assessment and research programs.