Ask a RIFM Scientist

Two people in lab coats having a discussion over a microscope and tablet
Headshot of Nikaeta Sadekar

If I can smell it, is it safe?

Nikaeta Sadekar, PhD, DABT

One hurdle to understanding fragrance is the misconception that there must be a lot of something if you can smell it. Human odor perception is so sensitive that it often takes very little of a substance—like a single drop of ink in a large tanker truck—to deliver a sharp, lasting note that tricks the brain into believing there’s a lot more of the molecule than there is.

A smell can have a strong emotional or psychological effect, and depending on the exposure, there can also be a physiological effect. But as a toxicologist, I would quote Paracelsus: “The dose makes the poison.”

In some cases, humans can smell and detect odors in parts per billion, much lower than the existing inhalation exposure reports we have on some fragrance ingredients. These reports show that it takes an exposure well above the “odor threshold” to manifest into any physiological effect, such as irritation. (“Odor threshold” is how scientists refer to the lowest concentration level where a person can detect a smell in their immediate environment.)

RIFM’s Database houses total chronic inhalation exposures from the highest users of fragranced products, and even these high-end user exposures are very low.

RIFM is now researching odor thresholds, updating earlier studies that looked at the mechanism in humans. Current science has replaced the techniques and study designs used back then with more sophisticated, refined versions.

We hope that scientifically measuring the odor thresholds will further our knowledge of how strong-smelling these fragrance ingredients can be. Learning about odor thresholds, in turn, may help consumers make better decisions about the products they are using in their daily routines.

Senior Scientist Nikaeta Sadekar, PhD, DABT, leads RIFM’s Respiratory Toxicology research and safety assessment programs.