Ask a RIFM Scientist: What is phototoxicity, and why does RIFM study it?


Maintaining healthy skin is essential to our overall well-being, especially regarding exposure from the sun.

That is why the Research Institute for Fragrance Materials (RIFM) has focused some of its research on the potential for light to activate fragrance materials resulting in reactions in the body’s largest organ, the skin.

Principal Scientist Gretchen Ritacco, MS, heads RIFM’s photoirritation and photosensitization research and safety assessment programs.

Q: What is phototoxicity?

A: Phototoxicity is a general term that refers to any skin reaction that occurs when an exogenous (not something your body made) substance is exposed to ultraviolet (UV) rays. The substance may be a medicine or a chemical. Typically, it is applied directly to the skin, although sometimes it is taken orally and makes its way to the skin. People can be exposed to UV rays from direct sunlight or artificial sources, such as tanning beds.

There are two kinds of phototoxicity:

In photoirritation, the affected area of skin may resemble an exaggerated sunburn. These one-time effects go away over time and occur in anyone given enough of the material and UV light.

Photosensitization reactions are an immune system response and resemble allergic contact dermatitis: red, bumpy, or itchy skin. The induction of photoallergy is rare and dependent on an individual’s immune system, but once induced, it persists, like any allergic response.

Q: Can fragrance ingredients cause phototoxicity?

A: An ingredient has to absorb UV rays to have phototoxic potential. Fortunately, about 94% of synthetic fragrance ingredients do not absorb UV rays.

In the absence of available study data, scientists must test any ingredient that does absorb UV light.

While our testing paradigm for photoirritation is clear cut, photosensitization testing is a challenge. Photosensitization testing in humans is not ethical because of the rare potential for causing persistent light reactions. Likewise, scientists avoid testing in animals whenever possible.

Q: How can RIFM be sure that newly developed fragrance ingredients will not cause photosensitization?

A: RIFM is collaborating with three different groups to investigate in vitro (non-animal, petri dish) methods of determining whether a fragrance material may cause photosensitization.

One partnership involves both IIVS, a non-profit organization dedicated to the promotion of non-animal test methods, and cosmetics manufacturer Shiseido.

In this three-way collaboration, we are looking at three separate assays to predict photosensitization. They are the same three assays used for skin sensitization but with an added UV irradiation step: photo-Direct Peptide Reactivity Assay (DPRA), photo-KeratinoSens, and photo-human Cell Line Activation Test (hCLAT).

These assays will provide us with information on whether, in the presence of UV light, the material binds to skin proteins, and if, in the presence of UV light, the material activates keratinocytes or dendritic cells. These are key events in the overall process of photosensitization.

The second partnership is with SenzaGen, a biotech company specializing in immunotoxicity studies done on genetic material in test tubes.

SenzaGen uses a skin assay called GARD (Genomic Allergen Rapid Detection) to predict the ability of chemicals to induce skin sensitization.

GARD uses a human myeloid leukemia cell line called SenzaCell, which acts as an in vitro model of human dendritic cells, which communicate with T cells to start up the immune process.

This collaboration will focus on modifying the GARD assay to include UV irradiation to predict photosensitization.

Through these two partnerships, RIFM expects to develop a toolkit of non-animal tests to help us ensure that consumers can safely enjoy their favorite fragranced products.