Would you give up your sense of smell to keep your hair? What about your phone?

A 2022 US study compared smell to other senses (sight and hearing) and personally prized commodities (including money, a pet or hair) to see what people valued more.

The researchers found smell was viewed as much less important than sight and hearing, and valued less than many commodities. For example, half the women surveyed said they’d choose to keep their hair over sense of smell.

Smell often goes under the radar as one of the least valued senses. But it is one of the first sensory systems vertebrates developed and is linked to your mental health, memory and more.

Here are five fascinating facts about your olfactory system.

1. Smell is linked to memory and emotion

Why can the waft of fresh baking trigger joyful childhood memories? And why might a certain perfume jolt you back to a painful breakup?

Smell is directly linked to both your memory and emotions. This connection was first established by American psychologist Donald Laird in 1935 (although French novelist Marcel Proust had already made it famous in his reverie about the scent of madeleines baking.)

Odours are first captured by special olfactory nerve cells inside your nose. These cells extend upwards from the roof of your nose towards the smell-processing centre of your brain, called the olfactory bulb.

From the olfactory bulb they form direct connection with the brain’s limbic system. This includes the amygdala, where emotions are generated, and the hippocampus, where memories are created.

Other senses – such as sight and hearing – aren’t directly connected to the lymbic system.

One 2004 study used functional magnetic resonance imaging to demonstrate odours trigger a much stronger emotional and memory response in the brain than a visual cue.

2. Your sense of smell constantly regenerates

You can lose your ability to smell due to injury or infection – for example during and after a COVID infection. This is known as olfactory dysfunction. In most cases it’s temporary, returning to normal within a few weeks.

This is because every few months your olfactory nerve cells die and are replaced by new cells.

We’re not entirely sure how this occurs, but it likely involves your nose’s stem cells, the olfactory bulb and other cells in the olfactory nerves.

Other areas of your nervous system – including your brain and spinal cord – cannot regenerate and repair after an injury.

Constant regeneration may be a protective mechanism, as the olfactory nerves are vulnerable to damage caused by the external environment, including toxins (such as cigarette smoke), chemicals and pathogens (such as the flu virus).

But following a COVID infection some people might continue to experience a loss of smell. Studies suggest the virus and a long-term immune response damages the cells that allow the olfactory system to regenerate.

3. Smell is linked to mental health

Around 5% of the global population suffer from anosmia – total loss of smell. An estimated 15-20% suffer partial loss, known as hyposmia.

Given smell loss is often a primary and long-term symptom of COVID, these numbers are likely to be higher since the pandemic.

Yet in Australia, the prevalence of olfactory dysfunction remains surprisingly understudied.

Losing your sense of smell is shown to impact your personal and social relationships. For example, it can mean you miss out on shared eating experiences, or cause changes in sexual desire and behaviour.

In older people, declining ability to smell is associated with a higher risk of depression and even death, although we still don’t know why.

4. Loss of smell can help identify neurodegenerative diseases

Partial or full loss of smell is often an early indicator for a range of neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases.

Patients frequently report losing their sense of smell years before any symptoms show in body or brain function. However many people are not aware they are losing their sense of smell.

There are ways you can determine if you have smell loss and to what extent. You may be able to visit a formal smell testing centre or do a self-test at home, which assesses your ability to identify household items like coffee, wine or soap.

5. You can train your nose back into smelling

“Smell training” is emerging as a promising experimental treatment option for olfactory dysfunction. For people experiencing smell loss after COVID, it’s been show to improve the ability to detect and differentiate odours.

Smell training (or “olfactory training”) was first tested in 2009 in a German psychology study. It involves sniffing robust odours — such as floral, citrus, aromatic or fruity scents — at least twice a day for 10—20 seconds at a time, usually over a 3—6 month period.

Participants are asked to focus on the memory of the smell while sniffing and recall information about the odour and its intensity. This is believed to help reorganise the nerve connections in the brain, although the exact mechanism behind it is unclear.

Some studies recommend using a single set of scents, while others recommend switching to a new set of odours after a certain amount of time. However both methods show significant improvement in smelling.

This training has also been shown to alleviate depressive symptoms and improve cognitive decline both in older adults and those suffering from dementia.

Just like physiotherapy after a physical injury, olfactory training is thought to act like rehabilitation for your sense of smell. It retrains the nerves in your nose and the connections it forms within the brain, allowing you to correctly detect, process and interpret odours.

Lynn Nazareth, Research Scientist in Olfactory Biology, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

More than 1,300 Victorians have joined a class action against Johnson & Johnson alleging its talcum powder products left them with ovarian cancer, mesothelioma (cancer affecting the lungs) and other cancers affecting the reproductive organs.

This follows lawsuits in the United Kingdom and the United States, including a prominent case in California. In December 2025, Johnson & Johnson was forced to pay two women US$40 million after a jury found its baby powder was dangerous and that it had failed to warn consumers.

Talc is a naturally occurring mineral mined in many parts of the world. People can come into contact with it during mining and processing, industrial applications, and more commonly, through its use in cosmetics and body powders.

People use talc on their genitals to absorb moisture, reduce friction, disguise odours, or to reduce skin rashes and chafing. Talc increases the opaqueness of face powders and cosmetics, leaving skin feeling smooth and soft.

So how is it linked to cancer? And what does the scientific evidence say?

Contamination with asbestos

Since the 1970s, questions have emerged about whether talc could be contaminated with asbestos. Asbestos is a cancer-causing agent that can affect the lungs when inhaled.

Talc and asbestos are minerals often found close to each other in the Earth, so there is potential for talc to be contaminated with asbestos during the mining process.

Since the 1970s, manufacturers have attempted to produce pure talcum powder free from asbestos. However, it’s unclear how routinely samples are tested and the extent of contamination over the past 50 years.

In 2023, Johnson & Johnson stopped selling talc in its products worldwide, including in Australia, switching instead to a cornflour base. Other manufacturers still sell talcum powder and it’s still used in cosmetics, as well as industrially.

What does the science say about the cancer link?

Two cancers have a possible link with talc use:

• lung cancer, due to the potential to inhale talc particles, which can occur with some types of jobs
• ovarian cancer, due to regular use of talcum powder in the genital area.

Some human studies have found products containing talc are linked with higher rates of ovarian cancer. Other studies have found no link.

Studies that examined the use of talc on the genital area found no evidence to suggest a link between talc and uterine or cervical cancer.

But there are several challenges to overcome when studying the link between talcum powder and cancer. It can be difficult to recall details about talc use (brand, amount, and so on) many years later. Some people who developed cancer will have died before being identified and studied, so won’t be included.

However, when researchers investigated how often participants used talc powder and compared those who used it frequently with those who didn’t, they found an increased risk of ovarian cancer among frequent users.

So what does it all mean?

When there are differing results from multiple studies, those results can be summarised together to answer the research question. So what does all the currently available evidence say about the relationship between talc usage and ovarian cancer?

This summary study concludes there appears to be a weak risk of some types of ovarian cancer, meaning it’s linked to a small increase in risk, but the reasons why remain unclear.

The evidence suggests talc does not increase the risk of other gynaecological cancers, such as uterine and cervical.

Talc contaminated with asbestos is clearly linked to an increased risk of lung cancer. However, cosmetic use of talc doesn’t seem to increase the risk of lung cancer because users don’t breathe it in.

In 2024 the World Health Organization (WHO) updated its advice to say that talc is “probably carcinogenic” which means it probably causes cancer in humans. This is the second-highest risk level for cancer, which includes the herbicide glyphosate (Roundup) and red meat.

If you use talcum powder and are concerned about an increased risk of cancer, it’s recommended you stop using it or limit how much you use. As with all decisions in life, consider the balance between potential harms and benefits, especially if you’ve used talc for a long time and want to minimise your risk of getting cancer.

Tam Ha, Associate Professor of Cancer Epidemiology, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.