This week, Professor Luke O’Neill turns his microscope to a condition he knows all too well — cellulitis.

It’s one of the most common bacterial infections there is, affecting about one in every 500 people each year. The skin turns red, swollen, and sore, and you might even feel flu-ish as your immune system fights back. Left untreated, it can spiral into sepsis, making early diagnosis vital.

Listener Joanie suggested this week’s theme, and you can do the same by emailing Luke at laoneill@tcd.ie. As Luke explains, cellulitis happens when bacteria slip through tiny breaks in the skin — a scratch, a cut, even an insect bite — and start multiplying. He suspects that’s how he picked it up himself earlier this year.

Rates of cellulitis are on the rise, with hospitals seeing more admissions, especially in settings where people live in close quarters: nursing homes, homeless shelters, and college dorms. Obesity and antibiotic resistance may also be fuelling the increase.

Treatment is straightforward (antibiotics usually clear it up) but prevention is even better. Keeping skin clean and moisturised, and treating any breaks promptly, can stop it taking hold.

And it’s not just humans. Cats, dogs and even horses can suffer from cellulitis, with vets watching closely for swelling and lameness. In fact, that old-fashioned poultice once used to “draw out” infection still has its place — at least in the stable.

From microbes to moisturiser, Luke explores how our skin keeps the world out. And what happens when it can’t.

This week, Show Me The Science gets a little darker — and a little stranger. Professor Luke O’Neill dives into the science of Hallowe’en, tracing its roots back to the Celtic festival of Samhain, the ancient Irish celebration marking the start of winter — that “dead time” when the veil between worlds was said to thin.

It’s not about ghosts and ghouls, Luke explains, but about remembering ancestors, lighting bonfires, and wearing masks to mark the turning of the seasons. Around those fires, people bonded, built resilience, and reaffirmed community — something modern psychology still recognises as vital in times of darkness and uncertainty.

Luke explores the science of fear: how the body reacts when startled, from adrenaline spikes to endorphin release, and why a good fright, once we recover from it, can actually make us stronger. Researchers have even measured these effects in saliva! But don’t expect Luke to be queueing up for a horror marathon — he admits he doesn’t get the same thrill others do from being scared senseless.

There’s also a scientific story behind our favourite monsters. The myths of vampires and werewolves, Luke reveals, may have stemmed from a rare inherited condition called porphyria, which causes sensitivity to light, red-stained teeth, and even hair growth and behavioural changes — symptoms that once seemed supernatural. And diseases like plague or tuberculosis, which sometimes left victims appearing to rise from the dead, helped fuel the legend of the undead.

From Bram Stoker’s Dracula — possibly inspired by both the actor Henry Irving and the medical realities of syphilis — to the theory that “Dracula” could derive from the Irish “droch fhola,” or “bad blood,” Luke connects folklore, medicine, and etymology in classic Show Me The Science style.

And there’s even a royal twist: King George III famously suffered from porphyria, and through royal intermarriage, the disease spread across Europe’s bloodlines — adding a touch of genetic truth to the vampire myth.

This special Hallowe’en edition was produced in collaboration with the Music Technology course at South East Technological University. The haunting original music was composed and recorded by Billy Doran.

Ever wondered what keeps your immune system in check when it starts misbehaving? On this week’s podcast, Professor Luke O’Neill explains the world of regulatory T cells—the immune system’s very own “military police.” These tiny guardians stop other cells from attacking the body, helping prevent autoimmune diseases and keeping us healthy.

Luke takes us through the Nobel Prize-winning discoveries of Mary Brunkow, Fred Ramsdell, and Shimon Sakaguchi, who cracked the secrets of immune tolerance. Back in 1995, Sakaguchi discovered these remarkable regulatory T cells, proving that the immune system is far more sophisticated than previously thought. Brunkow and Ramsdell uncovered the critical role of the Foxp3 gene in autoimmune diseases, and Sakaguchi later linked the Foxp3 gene to the development of these life-saving cells. Luke even shares insights from a recent encounter with Sakaguchi himself!

If you’ve ever been curious about how the body avoids attacking itself, or how groundbreaking immunology research leads to real-world insights, this episode is your backstage pass to the science of regulatory T cells.

Got questions, ideas, or thoughts for Luke? Email him directly at laoneill@tcd.ie

An Irish Olympian has decided to take a bold and controversial leap. Swimmer Shane Ryan has retired from conventional competition to join the Enhanced Games, a new event where athletes will be allowed to use performance-enhancing drugs.

In this week’s podcast, Professor Luke O’Neill looks at the science and the ethics behind this radical sporting experiment.

The Games’ creator, Aron d’Souza, says he wants to celebrate human potential without the limits imposed by anti-doping rules. Backed by investors such as Peter Thiel and Donald Trump Jr, the Enhanced Games are due to take place in Las Vegas in May 2026, offering up to a million dollars for breaking a world record.

Luke dives into the biology behind enhancement. He explains how testosterone builds muscle mass, how growth hormone boosts recovery, and how EPO (erythropoietin) increases red-blood-cell production and endurance. These substances can deliver extraordinary results, but they also carry dangerous side effects: heart damage, infertility, high blood pressure, diabetes, kidney failure, and even seizures.

Beyond drugs, the Games will also allow prosthetic limbs and high-tech running shoes, pushing the boundary between sport and science fiction. Critics, including the IOC and US Anti-Doping Agency, say it will destroy fair play. D’Souza insists athletes will be medically supervised and screened for safety.

Luke asks what this says about the times we live in — an “age of enhancement” where medicine, tech and ambition blur together. From longevity clinics to performance labs, we’re already chasing upgrades to our own biology.

It might sound like The Hunger Games, but it’s very real — and it’s coming soon.

Taylor Swift has changed her accent over the years – and science can prove it. A quirky new study from the University of Minnesota analysed hours of Swift interviews to show how her voice shifted depending on what era she was in. For Professor Luke O’Neill, it’s the perfect excuse to dive into one of his favourite subjects: accents and dialects.

From the five distinct dialects of Ireland to the 30-plus versions of English spoken worldwide, this week’s podcast looks at why we sound the way we do – and why accents change over time. He explains how Elizabethan English is still alive in pockets of North America, why Irish “borrow words” like galore, slew, baloney and hooligan have shaped English, and how the Beatles made regional accents cool in the 1960s.

There’s science, history, and plenty of fun in this trip through the way we speak – with Luke revealing his two favourite English accents (spoiler: think West Country warmth and Southern US drawl). And yes, he’s very happy that the Irish accent now ranks among the coolest in the world.

Got an accent story of your own, or an idea for a future episode? Drop Luke an email at laoneill@tcd.ie.

They look like alien spacecrafts under a microscope, but bacteriophages — viruses that infect and kill bacteria — could hold the key to one of the biggest medical challenges of our time: antibiotic resistance. First described more than a century ago, phages became a hot topic of research in the mid-20th century, especially in the Soviet Union, before slipping into obscurity with the rise of antibiotics. Now, with superbugs on the march and antibiotics losing their punch, phages are making a comeback.

On this week’s podcast, Professor Luke O’Neill dives into the fascinating history and biology of these tiny viral predators, from the Soviet labs of the Cold War to today’s cutting-edge clinical trials. He explains how phages can target deadly bacteria like Staphylococcus aureus and Pseudomonas aeruginosa, why their extreme specificity is both a blessing and a challenge, and how scientists are now combining phages with antibiotics to create new treatments. With fresh lab techniques making it easier to grow and manipulate phages, the field is buzzing with new potential.

Expect alien-looking viruses, a dash of Cold War intrigue, and real hope for tackling infections that antibiotics can no longer beat.

Got a topic you’d like Luke to cover? Email your ideas to laoneill@tcd.ie.

Earth has always been a planet of comebacks. Life has thrived, collapsed, and reinvented itself in astonishing ways. Scientists call the five great wipe-outs of the past the “Big Five” – huge mass extinctions that reset the clock on life. Without them, we wouldn’t even be here to talk about it.

This week, Luke O’Neill dives into what these extinction events can teach us - from the ancient Ordovician seas that suddenly emptied, to the Triassic era where one wave of destruction cleared the stage for the dinosaurs, and the dramatic end of the Cretaceous, when an asteroid put an end to their reign. The most catastrophic of all came at the end of the Permian, nicknamed “the Great Dying,” when nearly everything living was snuffed out.

What’s extraordinary is the sheer gulf of time between these cataclysms. Tens of millions – even hundreds of millions – of years separated one mass extinction from the next. To put it in perspective, the gap between the end-Triassic and the asteroid strike that finished the dinosaurs is longer than the time between that asteroid strike and today. These are planetary rhythms on a timescale that makes human history look like the blink of an eye.

But here’s the uncomfortable twist: many scientists now argue that we’re in the early stages of a sixth great extinction. And for the first time, it wouldn’t be volcanoes or asteroids doing the damage – it would be us. Human activity, from climate change to habitat destruction, is putting pressure on life everywhere.

So what does history tell us? That life will recover. But whether we will be part of that story depends on what we do next. Luke explores how science is helping us understand extinction not as an abstract tragedy, but as a warning sign – and why the choices humans make in the coming decades matter more than ever.

Send your feedback or ideas for future episodes to Luke at laoneill@tcd.ie.

Breast milk is often called “nature’s first vaccine” and, in this week's podcast, Luke O’Neill explains why. From the moment a baby is born, its immune system is still immature and wide open to infection. Breast milk steps in as the baby’s first line of defence, passing on antibodies, immune cells and even the benefits of vaccines the mother has received.

Luke explores how this “passive immunisation” works – from the placenta before birth to breast milk afterwards – and why it’s so powerful in protecting babies against infections, hospitalisations and even long-term risks like obesity and diabetes. He also looks at the benefits for mothers, including protection against breast and ovarian cancer, diabetes and high blood pressure.

Along the way we learn why Ireland still struggles with low rates of breastfeeding, how more support for new mothers could ease pressure on the health system, and why vaccinating during pregnancy is such a vital public health tool. Luke highlights new research on the RSV vaccine, which shows up to 80% protection for babies when mothers are immunised, and pays tribute to Dublin-born scientist Francis Bramble, who first uncovered the secrets of mother-to-baby immunity back in the 1930s. With a wink, Luke suggests it might be time to “Make Bramble Great Again.”

This episode is a reminder that breast milk isn’t just food – it’s medicine, protection, and an immune system tutor all rolled into one.

Send your feedback or ideas for future episodes to Luke at laoneill@tcd.ie.