Ask a RIFM Scientist

Two people in lab coats having a discussion over a microscope and tablet
Headshot of Mihwa Na

What is skin sensitization, and why study it?

Mihwa Na, PhD

First, it’s important to distinguish between skin sensitization and skin irritation. Each is a result of a different mechanism in the body.

Skin irritation is a temporary surface response—such as itchiness or redness—that happens almost immediately when coming in contact with an irritating substance, such as very hot water. It goes away after the source of irritation is removed and may not return, depending on many different factors.

On the other hand, skin sensitization is an immune response that only develops in a fraction of people and happens over time after repeated exposures to a substance. Once a person’s immune system has been sensitized to a specific substance, they will always experience an allergic reaction to it, often at lower levels of exposure.

Skin is the largest organ of the body, and skin health is critical to our overall health and quality of life. From soaps and shampoos to sunscreens and deodorants, fragrances in personal care products come in direct contact with our skin. Therefore, RIFM must conduct safety evaluations on all fragrance ingredients and base our safety assessments on real-world exposure levels.

Any fragrance ingredient identified as a sensitizer must be carefully managed. In those cases, the RIFM safety assessment details maximum concentration levels for ingredients based on the type of product in which the fragrance is used. The International Fragrance Association (IFRA) then sets and releases the Standards for new and existing formulations by which the Fragrance Industry is expected to comply.

As part of its ongoing safety assessment of individual fragrance ingredients, the Research Institute for Fragrance Materials (RIFM) gauges the impact of these ingredients on the skin to determine their risk for causing skin sensitization. Mihwa Na, PhD, leads RIFM’s skin sensitization team.