Författare: Primrose Freestone Senior Lecturer in Clinical Microbiology

There is a cognitive bias called “the curse of knowledge” (sometimes also called “the curse of expertise”). It happens when you incorrectly assume that everyone knows as much as you do on a given topic. As a clinical microbiologist, I assumed everyone knew that it was a terrible idea to kiss a newborn baby anywhere on its head.

Dr Karan Raj, an NHS surgeon, recently made a TikTok warning people of the dangers of kissing a baby and judging by the thousands of comments, this was news to many on the social media platform.

Late last year, a UK charity called The Lullaby Trust published the result of a survey which revealed that 54% of new and expectant parents would “let friends and family kiss their newborn baby, unaware of the risk of serious infection”.

But why is it so dangerous to kiss a newborn?

A baby’s immune system is not fully developed when they are born, so their risk of catching a serious infection is much higher.

For the first three months or so, the infant’s immune system has fewer innate infection-fighting immune cells, such as neutrophils and monocytes, compared with adults, which means that infections that cause mild symptoms in adults or older children can be life-threatening for babies.

The herpes virus infection is one such example. In adults, herpes causes cold sores, but babies can quickly become seriously ill after catching the virus. If the herpes only affects the baby’s eyes, mouth or skin, most will recover after antiviral treatment. But if the virus becomes systemic and affects the baby’s organs, the infection is much more serious and can even be deadly. The younger the baby, the more vulnerable they are to infection by herpes, particularly in the first four weeks after birth.

Newborn babies are also more vulnerable to infectious bacteria than older children and adults and are especially susceptible to infections with intracellular pathogens (bacteria that can enter and survive inside the cells of the host organism), such as group B streptococci (GBS). These bacteria often live in their host’s gastrointestinal and genital tracts without causing illness. GBS infections in babies cause sepsis, pneumonia, meningitis and blood infections.

Babies are also susceptible to infections by E coli strains that are not harmful to adults, causing them pneumonia, meningitis and sepsis, all of which can have serious outcomes.

E coli can also cause serious, even life-threatening, infections in newborns.
Alexey Kotelnikov / Alamy Stock Photo

Showing affection – safely

Parents of very young babies should not feel uncomfortable about asking visitors to avoid kissing or touching their child. If the visitor really cares for the wellbeing of the infant, they should not feel offended by the request. And the parents should not feel they are overreacting.

The kindest action of any visitor is to not put a baby at risk, but if for good reasons you must kiss the baby there are some things that can reduce the infection danger you pose.

First, make sure you wash your hands thoroughly. And avoid kissing the infant on the mouth or face. Kiss their foot or the back of their head. If you have an active infection of any kind, think about whether you really need to visit the baby at all, particularly if the child is less than a month old.

Herpes infections are particularly serious for very young babies, so cover up any cold sores with a dressing.

If you are unwell but feel you cannot stay away from visiting the child, wear a mask and avoid closely approaching the newborn, particularly if you have a respiratory illness.

Always keep in mind that babies are very vulnerable to infection. Although kissing them is a sign of love, it can make a newborn seriously unwell – and you’d feel terrible if that happened. Läs mer…

Demand for secondhand and vintage clothing has surged within the last few years. Pre-owned fashion is seen by many consumers as a cheaper, more environmentally friendly way to expand their wardrobe.

But as excited as you might be to wear your next secondhand purchase, it’s important you disinfect it properly first. This is because clothing can actually be an important reservoir for many infectious diseases.

The skin is naturally coated in millions of bacteria, fungi and viruses, collectively known as the skin microbiome. This means every item of clothing we wear comes into close contact with these microbes.

Many of the microbes that regularly call the skin microbiome home include the bacteria Staphylococcus (which causes staph infections), Streptococcus (the bacteria behind strep A), fungi such as Candida (the species of yeast that most commonly causes thrush) and viruses such as the Human papillomavirus (which causes HPV).

Each person’s skin microbiome is uniquely adapted to them. What’s normal and harmless for one person can be disease-causing to another.

Infection risk of used clothes

Clothing is a well-known carrier of many disease-causing pathogens. This means that germs from the original clothes owner’s unique skin microbiome could still be found on secondhand clothes if the items weren’t cleaned prior to selling. It also means that any infections or pathogens they might have had when they last wore the clothes could still be found there.

Research has found clothing can harbour many infectious pathogens – including germs such as Staphylococcus aureus (which causes skin and blood infections), bacteria such as Salmonella, E coli, norovirus and rotavirus (which can cause fever, vomiting and diarrhoea) and the fungi that can cause athlete’s foot and ringworm.

A survey of secondhand clothing specifically, which was being sold in a market in Pakistan, detected the presence of Bacillus subtilus and Staphylococcus aureus in many of the samples taken. These bacteria can cause skin and blood infections. Parasites which can cause skin infections (such as dermatitis and scabies) have also been found on secondhand clothing.

The skin’s microbes can live on the amino acids in sweat, as well as the sebaceous oil released from hair follicles and the proteins of skin cells, all of which are deposited into clothes when we wear them.

Not only that, but research shows many pathogenic germs – such as E coli, Staphylococcus aureus and Streptococcus pyogenes – can survive on clothes for months when kept at room temperature. Germs on cotton or mixed-fibre clothes stayed alive for up to 90 days. But on polyester fabrics, these germs lived as long as 200 days. Most bacterial species survived better in the fabrics when the air humidity was high. This suggests that to minimise germ growth, clothes should be stored in a dry environment.

Microbes can survive on clothes for many months.
Caftor/ Shutterstock

While it’s difficult to say how great your risk of actually contracting an illness from secondhand clothes is (as no study has been done to date), people who are immunocompromised are probably at the greatest risk. If you have an impaired immune system, you should take extra care before wearing secondhand purchases.

How to properly wash second-hand clothes

Most microbes need water to grow. Skin areas that tend to get moist – such as the armpits, feet and genital areas – tend to have the highest number and most diverse species of microbes. Fabric that has come in contact with these regions will be the most contaminated. Alongside bodily fluids, clothes can also become contaminated with traces of food debris. This could also act as a source of growth for any bacteria or fungi present.

This is why washing secondhand clothes is so important for preventing germ growth and reducing infection risk. One study of secondhand clothing contaminated with the scabies parasite even found that washing clothes eliminated all of the parasites present.

It’s recommended that you wash newly purchased secondhand clothes with detergent at a temperature of around 60°C. This will not only clean any dirt from the clothes, but will also remove germs and inactivate pathogens.

Cold water will not work as well to get rid of pathogens within clothing. So if a high-temperature wash isn’t possible, then use a laundry disinfectant to kill any germs present.

You should try to initially wash secondhand clothes separately from regular laundry to reduce cross contamination of clothing. Soaking the secondhand clothing in a separate bowl of hand-hot (not boiling) water with antibacterial laundry detergent for two to three hours should eliminate any pathogens present. Follow with a regular machine wash.

To be even more sure you eliminate any remaining germs, a hot tumble dryer or a steam iron treatment (again, around 60°C if your fabric allows it) is highly effective at killing bacteria, viruses and parasite eggs.

Although many secondhand clothes sellers say they wash clothing before selling, you can never be too sure. This is why it’s a good idea to wash any secondhand clothes you buy regardless. It’s probably also a good idea to wash any new clothes you buy before wearing as well. Läs mer…