Sunscreens can damage skin, researchers find

August 29, 2006
Sunscreens can damage skin, researchers find
Two-photon fluorescence intensity images of cells deep in the epidermis showing reactive oxygen species activity following sunscreen application to the skin surface. Reactive oxygen species can react with cellular components, leading to skin damage and increasing the visible signs of aging. Credit: K. Hanson, UC Riverside

Are sunscreens always beneficial, or can they be detrimental to users? A research team led by UC Riverside chemists reports that unless people out in the sun apply sunscreen often, the sunscreen itself can become harmful to the skin.

When skin is exposed to sunlight, ultraviolet radiation (UV) is absorbed by skin molecules that then can generate harmful compounds, called reactive oxygen species or ROS, which are highly reactive molecules that can cause "oxidative damage." For example, ROS can react with cellular components like cell walls, lipid membranes, mitochondria and DNA, leading to skin damage and increasing the visible signs of aging.

When sunscreen is applied on the skin, however, special molecules – called UV filters – contained in the sunscreen, cut down the amount of UV radiation that can penetrate the skin. Over time, though, these filters penetrate into the skin below the surface of the epidermis, the outermost layer of skin, leaving the body vulnerable to UV radiation.

Sunscreens can damage skin, researchers find
UV filters (octylmethoxycinnamate, benzophenone-3 and octocrylene) widely used in sunscreens generate reactive oxygen species (ROS) in skin when exposed to ultraviolet radiation, augmenting the ROS that is naturally produced. Credit: K. Hanson, UC Riverside

Led by Kerry M. Hanson, a senior research scientist in the Department of Chemistry at UCR, the researchers report that three UV filters (octylmethoxycinnamate, benzophenone-3 and octocrylene), which are approved by the Food and Drug Administration and widely used in sunscreens, generate ROS in skin themselves when exposed to ultraviolet radiation, thus augmenting the ROS that is naturally produced. The researchers note that the additional ROS are generated only when the UV filters have penetrated into the skin and, at the same time, sunscreen has not been reapplied to prevent ultraviolet radiation from reaching these filters.

Study results will appear in an upcoming issue of Free Radical Biology & Medicine. An advance copy of the paper is available online on the journal's Website.

"Sunscreens do an excellent job protecting against sunburn when used correctly," said Hanson, who works in the laboratory of Christopher Bardeen, an assistant professor of chemistry at UCR. "This means using a sunscreen with a high sun protection factor and applying it uniformly on the skin. Our data show, however, that if coverage at the skin surface is low, the UV filters in sunscreens that have penetrated into the epidermis can potentially do more harm than good. More advanced sunscreens that ensure that the UV-filters stay on the skin surface are needed; such filters would reduce the level of UV-induced ROS. Another solution may be to mix the UV-filters with antioxidants since antioxidants have been shown to reduce UV-induced ROS levels in the skin."

In their research, Hanson and colleagues used epidermal model tissue and applied sunscreen to the surface to test the effect of sunscreen penetration on ROS levels in the deep epidermis. A two-photon fluorescence microscope allowed them to visualize ROS generation occurring below the skin surface. The ROS activity was detected using a probe molecule whose fluorescent properties change upon exposure to ROS. On comparing images taken before and after the skin was exposed to UV radiation, they found that ROS generation in the skin increased after sunscreen penetration.

About 95 percent of the visible signs of aging are associated with UV exposure. About 90 percent of a person's total life-time UV exposure is obtained before the person is 18 years of age. Only a few UV-filters are available that block "UV-A," the wavelengths that penetrate more deeply into the skin, all the way into the dermis where collagen exists.

"For now, the best advice is to use sunscreens and re-apply them often – the Skin Cancer Foundation recommends every two hours, and especially after sweating or swimming, which can wash away sunscreen – to reduce the amount of UV radiation from getting through to filters that have penetrated the skin," Bardeen said. "This, in turn, would reduce ROS generation."

Next, the researchers plan to investigate the effect of smog on ROS generation in the skin.

Source: University of California - Riverside

Explore further: Unexpected factor contributes to melanoma risk in red-haired, fair-skinned individuals

Related Stories

Unexpected factor contributes to melanoma risk in red-haired, fair-skinned individuals

October 31, 2012
The well-established elevated risk of melanoma among people with red hair and fair skin may be caused by more than just a lack of natural protection against ultraviolet (UV) radiation. In an article receiving Advance Online ...

Melanoma: Scientists find new link between pigment production and mitochondrial function

January 5, 2015
A new research report published in the January 2015 issue of the FASEB Journal helps explain what goes wrong to when someone gets skin cancer and the relationship between changing skin pigment and the cancer itself. In particular, ...

Sun cream compound offers unprecedented protection against UVA radiation

July 20, 2016
A new compound developed by University of Bath scientists in collaboration with King's College London offers unprecedented protection against the harmful effects of UVA radiation in sunlight, which include photo-ageing, cell ...

Red hair pigment might raise melanoma risk, study says

May 9, 2013
(HealthDay)—The red in redheads' hair is thought to put them at increased risk of the dangerous skin cancer melanoma, even if they don't spend a lot of time in the sun, according to a new study.

Recommended for you

Maintaining sufficient vitamin D levels may help to prevent rheumatoid arthritis

November 20, 2017
Maintaining sufficient vitamin D levels may help to prevent the onset of inflammatory diseases like rheumatoid arthritis, research led by the University of Birmingham has discovered.

Dementia study sheds light on how damage spreads through brain

November 20, 2017
Insights into how a key chemical disrupts brain cells in a common type of dementia have been revealed by scientists.

Car, stroller, juice: Babies understand when words are related

November 20, 2017
The meaning behind infants' screeches, squeals and wails may frustrate and confound sleep-deprived new parents. But at an age when babies cannot yet speak to us in words, they are already avid students of language.

Now you like it, now you don't: Brain stimulation can change how much we enjoy and value music

November 20, 2017
Enjoyment of music is considered a subjective experience; what one person finds gratifying, another may find irritating. Music theorists have long emphasized that although musical taste is relative, our enjoyment of music, ...

Researchers discover a new target for 'triple-negative' breast cancer

November 20, 2017
So-called "triple-negative" breast cancer is a particularly aggressive and difficult-to-treat form. It accounts for only about 10 percent of breast cancer cases, but is responsible for about 25 percent of breast cancer fatalities.

Researchers discover key signaling protein for muscle growth

November 20, 2017
Researchers at the University of Louisville have discovered the importance of a well-known protein, myeloid differentiation primary response gene 88 (MyD88), in the development and regeneration of muscles. Ashok Kumar, Ph.D., ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.