Explainer: Why common hand sanitisers offer limited protection against viruses

Explainer: Why common hand sanitisers offer limited protection against viruses - Handwashing helps prevent foodborne illnesses including cholera, typhoid, and infections from Salmonella and E. coli. (Photo: Magnific)

Washing hands with soap and water remains important, particularly after using the toilet, before eating or preparing food, and when hands are visibly dirty. Alcohol-based sanitiser can be used when soap and water are unavailable.

Hand sanitisers can kill many bacteria and viruses on the hands, but their protective effects do not last long after application. Hands can become contaminated again within minutes as people touch shared surfaces, handle money, use phones or shake hands with others, experts say.

Germs are part of everyday life, and people come into contact with them through routine activities. Door handles, public transport rails, shopping trolleys, mobile phones and shared office equipment can carry microorganisms deposited by other people. When a person touches a contaminated surface, some of these germs may transfer to their hands.

The risk of infection increases when contaminated hands touch the eyes, nose or mouth, giving some viruses and bacteria a pathway into the body. People may do this without noticing, especially when rubbing their eyes, adjusting their glasses or eating.

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Not every germ picked up from a surface causes illness, and many respiratory infections spread mainly through particles released when an infected person breathes, talks, coughs or sneezes. However, hand hygiene remains an important way to reduce the transfer of germs and lower the risk of some infections.

Alcohol-based hand sanitisers work by rapidly inactivating many microorganisms on the hands. They are particularly useful when soap and running water are unavailable. However, most conventional products offer little lasting antimicrobial protection after the alcohol evaporates. Hands can therefore become recontaminated after touching contaminated objects.

This means that applying sanitiser once does not protect the hands throughout the day. Repeated use, particularly after activities that may contaminate the hands, can help reduce the risk of transferring germs to the face or food.

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A study published in Scientific Reports examined whether a specially formulated sanitiser designed to remain active on the skin for longer could offer additional protection against respiratory symptoms.

The study involved 568 adults from 417 households who were followed for 72 days between December 20, 2023, and February 29, 2024. Participants were divided into two groups and asked to use different sanitisers five to 10 times daily while recording their usage and health symptoms.

One group used a specially formulated sanitiser containing 62 per cent ethanol, lactic acid and 0.05 per cent benzalkonium chloride. The other used a commercially available sanitiser containing 79.7 per cent ethanol.

The specially formulated product was designed to provide antimicrobial activity on the skin for longer than conventional alcohol-based sanitisers.

The researchers found that 35 participants using the specially formulated product developed upper respiratory symptoms, compared with 58 participants using the conventional sanitiser.

The rate of illness was 12.3 per cent in the specially formulated group and 20.5 per cent in the conventional sanitiser group, representing an approximately 40 per cent lower incidence in the first group.

For the study, respiratory symptoms included a temperature of at least 37.8 degrees Celsius accompanied by a cough, sore throat or runny nose.

The researchers also found that fewer participants using the specially formulated sanitiser experienced work restrictions due to illness. These restrictions, which included missing work or working remotely, affected 14.7 per cent of participants in the specially formulated group, compared with 23.7 per cent in the conventional sanitiser group.

The findings suggest that the type of sanitiser used may influence health outcomes, although they do not prove that the specially formulated product directly prevented respiratory infections.

The researchers said the formulation may have offered additional benefits because of its potential to remain active on the skin after application. Earlier testing had suggested it could provide antimicrobial activity for up to two hours under the conditions examined.

However, the study did not directly measure how long the product remained active on participants' hands or whether it reduced the number of germs acquired from contaminated surfaces.

The results should also be interpreted with caution because the illnesses were based on symptoms reported by participants rather than laboratory tests confirming specific infections. The study did not include a group that used no sanitiser, meaning it could not determine the absolute protective effect of either product compared with not using sanitiser.

Both groups used their products an average of 5.7 times a day, suggesting that differences in application frequency did not account for the results.

The researchers said, “These findings suggest that the residual antimicrobial activity of the study formulation may have contributed to the observed between-group differences and may provide additional benefits for hand hygiene in community settings”.

The findings do not mean that conventional hand sanitisers are ineffective or that people should reduce their hand hygiene practices. Washing hands with soap and water remains important, particularly after using the toilet, before eating or preparing food, and when hands are visibly dirty. Alcohol-based sanitiser can be used when soap and water are unavailable.

The researchers recommended further studies involving more diverse populations to confirm whether the specially formulated sanitiser consistently reduces respiratory symptoms and illness-related work restrictions.