Skin Deep - Clinical & Cosmetic Dermatology Blog

Skin Deep is a blog for dermatologists and skin care professionals with focus on theoretical, cosmetic and aesthetic dermatology. This blog is associated with ‘Dermatologists Sans Borders’ one of the largest curated groups of skin care professionals on facebook. If you are looking for non-technical information, please visit

Emollients and Phototherapy in Psoriasis

Traditionally patients are advised not to apply emollients prior to phototherapy as emollients can have a sunscreen effect leading to sub optimal response to phototherapy. Is this always true?

A very close look at the optical properties of skin shows that emollients can actually be a double edged sword.

As light passes from one medium to another of different refractive indices, part of it gets reflected. The amount of light reflected depends on the difference of refractive index between the media.

In psoriasis the air between the scales creates multiple refractive surfaces leading to loss of UV during phototherapy. Hence if we can use an emollient with a refractive index similar to skin it can actually increase the penetration of UV.

This is not just a theoretical concept. Studies have shown that there are emollients with Monochromatic Protection Factor (MPF) in the 313-315 range (Narrow Band UVB) of less than 1, which means that penetration is more than uncovered skin!

Hence emollient manufacturers should think about introducing products tailor made for psoriasis patients on phototherapy.

If anybody want to explore this concept further or need help with MPD determination do contact me.

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About Me

As a Dermatologist and Informatician my research mainly involves application of bioinformatics techniques and tools in dermatological conditions. However my research interests are varied and I have publications in areas ranging from artificial intelligence, sequence analysis, systems biology, ontology development, microarray analysis, immunology, computational biology and clinical dermatology. I am also interested in eHealth, Health Informatics and Health Policy.


Bell Raj Eapen
Hamilton, ON