Carla M. Delgado is a health and culture writer based in the Philippines.

Heather Mercer is native to Northwest Ohio (go Walleye!) and graduated from Loma Linda University with two doctorate degrees (psychology and public health). She is currently a professor at Owens Community College, as well as a fact-checker for Verywell Health. She has gained experience in a variety of settings, ranging from corporate wellness and preventive medicine, to mental health, chronic disease, and end-of-life care. 

Frequent COVID-19 testing increases the chance of early detection. Finding out that you have COVID sooner rather than later gives you a chance to get treated to avoid complications and lets you know that you need to isolate and take steps to prevent spreading the virus to others.

The currently used COVID tests work by detecting either the genetic material of the SARS-CoV-2 virus itself or the biological markers of the virus. These tests require a sample to be taken from a person's nose or throat.

In a new study, researchers from the University of Surrey collected sebum, blood, and saliva samples from 83 hospitalized patients—some of whom had COVID. Using the samples, the researchers tested the different biofluids for virus biomarkers and got some surprising results.

Polymer chain reaction (PCR) tests are the "gold standard" for diagnosing COVID because they look for the virus itself in a sample taken from a person's mouth, nose, or throat.

However, Matt Spick, a postgraduate researcher at the University of Surrey and an author of the new study, told Verywell that sebum-based testing showed surprisingly good results in their research.

Sebum is the oily substance that's secreted by the body's sebaceous glands in the skin.

Spick said that in their study, blood-based testing for COVID biomarkers was 97% accurate. Sebum- and saliva-based testing were 88% and 80% accurate, respectively.

Although sebum swabs are not commonly used for testing, it is a growing area of research—and not just for COVID. For example, scientists at The University of Manchester have found that sebum might have the potential to identify biomarkers for Parkinson's disease.

“We also know that other viruses modify the skin,” said Spick. “Flavivirus modifies its host’s skin to make it more attractive to mosquitoes, helping the virus to propagate. We think sebum skin swabs have lots to tell us about what is going on elsewhere in the body.”

According to Spick, skin swabs have a few advantages: they are convenient and less painful to collect than other bodily fluids, and they may not be as likely to get contaminated.

Mark Loafman, MD, MPH, a family physician and chair of the Family and Community Medicine Department at Cook County Health, told Verywell that a test with those features would be welcomed.

"There's always hope for diagnostic testing that is more accurate, faster, less expensive, and ideally less invasive," said Loafman. "The invasive nature of a nasal swab or blood draw can be a disincentive for some adults and many children.”

Loafman said that investigating new sampling techniques could also be an opportunity to discover new insights about the body’s response to infection and the health condition being tested. In turn, that knowledge could lead to breakthroughs in treatment and prognosis.

We hope that our research will lead to further investigation of the potential of non-invasive sampling, either for specific conditions such as Parkinson’s Disease, or perhaps even for the next pandemic.

However, the COVID testing methodology in the study is still in the experimental stage, and Loafman said we'll be using traditional biofluid samples for the foreseeable future.

According to Spick, there is an established infrastructure for PCR and rapid antigen tests, which means that skin swab testing is a lower priority for now.

“Our study was small, and would need substantial validation work,” said Spick. “We hope that our research will lead to further investigation of the potential of non-invasive sampling, either for specific conditions such as Parkinson’s Disease, or perhaps even for the next pandemic.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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Centers for Disease Control and Prevention. COVID-19 testing: What you need to know.

Spick M, Lewis HM, Frampas CF, et al. An integrated analysis and comparison of serum, saliva and sebum for COVID-19 metabolomics. Sci Rep. 2022;12(11867). doi:10.1038/s41598-022-16123-4

Sinclair E, Trivedi DK, Sarkar D, et al. Metabolomics of sebum reveals lipid dysregulation in Parkinson’s disease. Nature Communications. 2021;12(1). doi:10.1038/s41467-021-21669-4

Zhang H, Zhu Y, Liu Z, et al. A volatile from the skin microbiota of flavivirus-infected hosts promotes mosquito attractiveness. Cell. 2022;185(14):2510-2522.e16. doi:10.1016/j.cell.2022.05.016

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