Since the advent of Covid-19, hand sanitisers have become part of everyday life, an instant and convenient way to wash your hands to prevent the spread of the coronavirus.

Or so it is commonly believed.

However, do you know what is really in that bottle? What “germs” does it actually kill? Are the chemicals even safe for frequent and long-term use on skin?

Unfortunately, there is no clear answer for the consumer. There are many different formulations on the market, their labelling is often incomplete, and most countries do not regulate these products.

Hand sanitisers typically contain antiseptic substances to kill “germs”, including viruses, bacteria and fungi. But these germs are very different from one another and react differently to antiseptics.

COMPOSITION AND EFFECTIVENESS 

Hand sanitisers are loosely categorised as alcohol-based and non-alcohol-based. Alcohol-based sanitisers commonly contain ethanol or isopropanol, while non-alcohol-based ones usually use benzalkonium chloride or chlorhexidine gluconate.

In relation to the Covid-19 pandemic, the World Health Organization (WHO) recommends alcohol-based sanitisers as they are more effective against viruses than the non-alcohol-based ones. 

Benzalkonium chloride and chlorhexidine gluconate are more effective against bacteria than against fungi and viruses, destroying bacteria by disrupting their plasma membrane.

They are generally effective against enveloped viruses (for example, the coronavirus), but ineffective against non-enveloped viruses (for example, rotavirus and adenovirus). Compared to alcohol, they are less fast-acting but they have greater residual activity.

Besides the active ingredient, hand sanitisers may also contain other additives.

These include:

• Emollient (for example, glycerol) to prevent dry skin

• Antimicrobial preservative (for example, hydrogen peroxide) to prevent the growth of contaminating bacterial spores

• Bittering agent (for example, methylethylketone and denatonium benzoate) to make the product less palatable and thus reduce the risk of ingestion 

• Fragrance to increase product appeal

The effectiveness of the active ingredients may be reduced by the additives.

There is no single international standard for testing the effectiveness of hand sanitisers.

Manufacturers have a choice of at least six standards that differ in the procedures and species of germ used for testing.

One testing standard widely used in the United States and Canada is called ASTM-E1174.

The test procedure involves the contamination of hands with a bacterial suspension, followed by rubbing the hands with the test hand sanitiser.

The surviving bacterial cells are recovered from the hands and measured using microbiological techniques. 

A control is also performed to provide a baseline for calculating the log reduction in cell count.

For this standard, the bacteria used are Serratia marcescens or Escheriichia coli and do not cover viruses or fungi.

NOT A MAGIC BULLET

Even if it passes the test, a hand sanitiser is not a magic bullet.

Studies have shown that washing hands with soap and water kills germs more effectively than using hand sanitisers.

As such, hand sanitisers are just a stopgap when soap and water are not available.

Another misconception is that the higher the alcohol content, the better. The US Food and Drug Administration recommends 60 to 95 per cent levels of alcohol for hand sanitisers.

Beyond 95 per cent, the rate of kill decreases rapidly as the alcohol evaporates too fast.

Alcohol acts by denaturing proteins, which does not occur easily in the absence of water. Pure alcohol is completely ineffective, as the alcohol needs water to do its job.

Different authorities recommend slightly different optimal proportions of active ingredients, but there should be at least 60 per cent ethanol or isopropanol, 0.1 to 0.15 per cent benzalkonium chloride, or 0.5 to 2.0 per cent chlorhexidine gluconate.

But even if the best formula is used, a person’s hands will not be completely stripped of viruses.

Sanitiser manufacturers often claim kill rates in excess of 99 per cent. For example, 99.99 per cent means that out of a million germs on your hands, just 100 of them will survive the sanitiser.

But these surviving germs continue to pose a health hazard as they can multiply again when conditions are favourable.

Product claims may mislead people into thinking the sanitiser will kill everything and there is no more need for good hand hygiene.

Hand sanitisers are recommended when soap and water are not accessible.

Besides causing irritation and drying effects to the hands, the excessive use of hand sanitiser may kill the good germs that protect against bad germs.

It is mostly left to consumers to contend with the unknowns and potential safety risks when shopping for hand sanitiser.

It does not help that labels are often incomplete, with ingredients listed but not their concentrations.

In Singapore and most other countries, hand sanitisers are not subject to pre-marketing approval by the regulatory authority for their importation, manufacture and sale.

The onus is on dealers to ensure that the hand sanitisers are safe for use and conform to guidelines.

The Health Sciences Authority of Singapore provides useful guidelines on claims, labelling and the supplier’s responsibilities for hand sanitisers.

REGULATIONS AND COMPLIANCE

However, hand sanitisers sometimes fall short of standards.

For example, there have been cases of methanol poisoning in the US from the use of hand sanitisers containing methanol. This type of alcohol is cheap, but toxic.

It can cause nausea, blindness, seizures and even death when absorbed through the skin in sufficient quantities.

Canada is one country with strict legislation on the manufacture and sale of hand sanitisers.

Manufacturers of hand sanitisers are required to comply with good manufacturing practices as stipulated in the legislation, while the labelling of hand sanitisers are required to comply with the product licence granted by Health Canada. 

Under Canada’s Food and Drugs Act, it is illegal to advertise hand sanitisers in a false, misleading or deceptive manner. All claims for the hand sanitisers must be consistent to what is approved in the product licence.

However, the strict regulation of hand sanitisers may not work everywhere as it will incur compliance costs and push up prices.

In Singapore, it is possible that hand sanitisers are not subject to the requirement of a pre-marketing product licence by the regulatory authority because of the perceived lower risk profile of hand sanitisers, as compared to other health products like pharmaceuticals, biopharmaceuticals, medical devices and vaccines. 

These therapeutic, diagnostic and other health products have the potential to pose more serious problems when they are not properly manufactured, distributed and used.

It is a known fact that tighter regulations can add compliance costs, which can in turn affect the prices of any regulated health product, and ultimately their comparative affordability and availability to consumers.

Consumers should always inspect the label on a bottle of hand sanitiser and be suspicious if key information is missing, such as a detailed list of ingredients, instructions for use or an expiry date.

They should check with the authorities if they are unsure of the manufacturer’s claims, such as claims of being effective against specific types of virus or claims of being recommended by doctors.

Ultimately, the best safeguard is to arm consumers with the awareness and knowledge to make informed choices.

ABOUT THE AUTHORS:

Associate Professor Chan Lai Wah is a pharmaceutical scientist in the Department of Pharmacy, Faculty of Science, National University of Singapore. Tan Ying Ting is a final year pharmacy student in the same university.