Visible light triggers pigmentation differently across skin types

Sunlight contains more than ultraviolet rays. According to a study published in the Journal of Investigative Dermatology, visible light — the portion of the spectrum the human eye can see — is a major trigger of skin pigmentation, alongside UV radiation.

The effect, researchers found, is not uniform. It depends heavily on Fitzpatrick Skin Phototype (FSPT), a clinical scale that classifies skin by its response to sun exposure. According to the study, people with phototypes III through VI — generally those with medium to dark skin — experience a measurable pigmentary response when exposed to visible light. People with phototypes I and II, who tend to have lighter skin, are more likely to experience erythema, or redness, rather than pigmentation.

The distinction matters because it points to melanin's central role. Pigmentation is, in effect, the skin's protective response to light exposure, and that response depends on how much melanin the skin can produce and deploy. For people with albinism — whose melanin production is significantly reduced or absent — neither response functions in the usual way.

What this means for sun protection research

The finding, as cited from Kohli et al. (2019) within the study, raises questions about how sun protection guidelines are designed. Most SPF testing and UV protection standards are built around UV radiation. If visible light is also a significant factor in skin response, protection recommendations that focus only on UV may leave gaps — particularly for people with phototypes at either end of the scale.

For people with albinism, who sit outside the typical phototype framework due to absent or minimal pigmentation, these gaps may be more consequential. Existing SPF products are tested against UV radiation; visible light protection is rarely measured or labelled.

The research does not yet offer clinical recommendations specific to albinism. But it adds weight to the argument that sun protection science must account for the full spectrum of light, not only the ultraviolet portion.