Genetic defect weakens skin barrier, increases absorption of common household chemicals

LUND, Sweden – The human body defends itself against harmful chemicals with a complex biological armor. You may know it better as skin. The strength of this armor is a hereditary trait, according to a team from Karolinska Institutet and Lund University. The new study finds that individuals who inherit a genetic mutation absorb three common household chemicals more quickly through their skin.

According to the Centers for Disease Control (CDC), most people encounter dozens of chemicals every day from household products for cleaning and self-care. Scientists refer to a chemical exposure on the skin as a dermal exposure. Certain chemicals can transfer from the outer surface of the skin to the inside through a process called dermal absorption. Once absorbed, chemicals can enter the bloodstream and lead to systemic toxicity if the dose and duration of exposure are high enough.

Filaggrin is an important component of skin

Whether chemicals are absorbed more quickly largely depends on characteristics of the outermost layer of skin, called the stratum corneum. Moreover, if the stratum corneum is damaged, dry, or otherwise impaired, chemicals can enter the body rapidly. A component of the stratum corneum, filaggrin, is essential for the stratum corneum’s barrier integrity. In other words, filaggrin is key for maintaining the body’s armor.

Prior studies have revealed that people are more prone to certain skin conditions if they have variation in the filaggrin gene meaning a different number of DNA bases than average. People with filaggrin variation also have increased uptake of certain chemicals. The research team wanted to clarify if dermal absorption of chemicals is increased in people with a filaggrin mutation.

The team focused on how filaggrin mutations influence skin absorption of three commonly encountered chemicals: pyrimethanil (a pesticide), oxybenzoate (a UV-light filter in sunscreen), and pyrene (a hydrocarbon in firewood smoke).

The researchers screened over 400 people in Sweden to gather their genetic information. Approximately 6.5 percent of these people had a filaggrin mutation, which is representative of the population in northern Europe.

The researchers next brought people with filaggrin mutations to the lab for a skin test. For the test, the researchers administered a harmless dose of three chemicals on their skin for four hours.

A weakened skin barrier

The researchers analyzed the urine of each participant to see how much of the chemicals were metabolized and excreted after passing through the skin. Pyrimethanil and pyrene transferred across the skin faster in people with filaggrin mutations. However, more pyrimethanil and oxybenzone was absorbed. This suggests that people with an impaired skin barrier absorb the pesticide faster.

“We found, for example, twice as high a dose of the pesticide in the people with a mutation compared with those without. The fact that the skin takes up a greater amount of certain chemicals as a result of a genetic variation could mean that people with this mutation get a higher internal dose,” says Dr. Karin Broberg in a university release.

A higher internal dose refers to the amount of chemical that gets absorbed into the body.

An important limitation of the study is that it didn’t assess skin barrier integrity of people with filaggrin mutations. Nevertheless, the study is the first to establish the link between filaggrin genetics and differences in skin absorption of chemicals.

Next, the researchers want to investigate what this means for skin conditions provoked by chemical exposures, such as eczema.

The study is published in the journal Environmental Health Perspectives.

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