Cold Comfort: What Winter Rituals Got Right About Microbes

Summary

Why do we fill our homes with evergreen branches, spices, candles, and citrus in winter? Across centuries and cultures, people developed winter traditions to bring warmth, light, and flavor into the darkest season, but many of those customs had unintended health benefits, too. Long before germ theory, winter rituals quietly reduced infection risks, preserved food safely, ventilated homes, and supported immune systems during the most vulnerable time of year.

In this episode of Infectious Dose, we explore how seasonal practices—like pomanders, fermentation, holiday cleaning, and even caroling—offered surprising protections against infectious diseases. This is the story of how humanity survived the cold, one ritual at a time. We also discuss why winter viruses still thrive today—and what ancient wisdom, combined with modern science, can teach us about staying well.

Listen here or scroll down to read full episode.

Full Episode

There’s something magical about winter traditions. The light in a dark month. The warmth against the cold. The rituals that feel ancient even when we don’t remember where they came from. But what we rarely realize is that many of these traditions—across cultures, continents, and centuries—carried hidden advantages in the fight against infectious disease. Not because people designed them as health measures, but because humans have always been trying to survive winter, long before we understood what microbes were.

This is Cold Comfort: What Winter Rituals Got Right About Microbes

Let’s unwrap the surprising epidemiology of winter holidays.

I want to start with something as simple as an orange in a Christmas stocking. In Victorian England it was a prized treat, a little burst of sunshine in a season without much color. In Japan, children receive mikan—winter mandarins—during the New Year festivities. Across Europe, St. Nicholas traditions included gifting citrus, sometimes the only fresh fruit a family might see all winter. None of these cultures understood vitamins. But every child eating that orange was getting a precious bit of vitamin C during the months when respiratory diseases hit hardest. And while vitamin C doesn’t prevent colds, it does support the immune system at a time of year when nutritional deficiencies were common and immunity was under strain. While the evidence is mixed, some studies—especially in people under physical stress or with limited diets—suggest vitamin C may modestly reduce the duration or severity of colds. A small but meaningful nutritional buffer that made a difference—especially when winter diets were strained.

Food traditions carry these little protective echoes everywhere. Think about the spices that define winter: cinnamon, cloves, ginger, nutmeg. These spices aren’t just seasonal comfort—they’re powerfully antimicrobial, antiviral, antifungal, and in some cases even insect-repellent. Cinnamon inhibits fungal growth and disrupts bacterial membranes. Cloves contain eugenol, a compound so potent it’s still used in dentistry for its antiseptic properties. Ginger reduces inflammation in the respiratory tract and shows mild antiviral activity against certain seasonal viruses. Nutmeg contains compounds that slow bacterial growth, especially in foods stored for long periods. Many of these spices entered winter cooking because they helped stretch the safety of preserved foods—especially when cold months meant relying on stored grains, root vegetables, dried fruit, or wine that might otherwise harbor spoilage organisms. Of course, their antimicrobial power depends on how much you use—culinary doses aren’t sterilizing, but they’re strong enough to delay spoilage and help preserved foods stay safe through the cold months.

And you see versions of this everywhere. In parts of Europe, glühwein—hot, spiced mulled wine—was heated with cinnamon and cloves not for aesthetic flair, but because spiced, warmed beverages were microbiologically safer than cold drinks made from questionable stored water or barrels. In India, winter chai spice blends did double duty: warming the body in cold months and suppressing microbial risks in milk, which was more vulnerable to contamination before refrigeration. In the Middle East, cardamom-spiked coffee served during winter gatherings provided another antibacterial boost—cardamom inhibits several foodborne pathogens. Mexican (ponsh) ponche, a traditional warm fruit punch served during Las Posadas, includes cinnamon and tejocote, both of which bring natural antimicrobial compounds to the mix. Even Scandinavian winter baking—like Swedish and Norwegian ginger snap cookies—was essentially antimicrobial architecture: spices allowed baked goods to last longer in cold but humid kitchens where mold could creep in.

None of this was intentional germ theory. It was simply people noticing that certain combinations of heat, spice, and fermentation kept their families healthier. Over centuries, those observations turned into tradition. And today, we keep those flavors because they taste like the holiday season—but the microbiology behind them is still there, quietly humming under the cinnamon and cloves.

Even holiday decorations weren’t always just decorations. Pomanders—citrus fruits studded with cloves—were used in medieval and early Renaissance Europe as plague charms. Not because they protected against Yersinia pestis, of course, but because they genuinely made foul, stagnant indoor air a little safer. Cloves release eugenol, which suppresses the growth of bacteria and molds. Citrus peels release limonene and other volatile compounds that repel insects, including fleas—the very vectors of plague. So while pomanders didn’t “ward off” disease in a supernatural sense, they did deter fleas from bedding and clothing, and they helped mask or reduce the odor of overcrowded winter rooms where respiratory infections also spread. In an era before sanitation and waste management, a scented object that repelled insects and freshened the air was legitimately useful.

And this practice wasn’t unique to Europe. Across North Africa and the Middle East, people hung or burned dried citrus peels, myrtle, or bay leaves in winter homes—plants known now to contain antimicrobial essential oils. In China, bundles of aromatic herbs like mugwort or wormwood were hung in the house during the darkest months for similar reasons: they suppressed insects and made enclosed spaces more breathable. In Scandinavia, evergreens brought inside for Yuletide weren’t just symbolic; the resins in pine and fir release compounds with mild antimicrobial and deodorizing effects. These trees were essentially nature’s air purifiers. Even Victorian kissing balls—those round bunches of holly, rosemary, and evergreen—originated as fragrant bundles meant to cleanse the air long before they became romantic décor.

So when pomanders re-emerged as a Victorian Christmas staple, the people using them had long forgotten the original logic. To them, the scent was simply festive and nostalgic. But underneath the nostalgia was a leftover fragment of ancient public health—a little sphere of citrus and spice that carried centuries of practical, microbial wisdom.

And then there’s fermentation. Few winter traditions have done more to keep people safe—accidentally—than the art of preserving food with microbes. In Korea, families gathered for kimjang, the ritual of making vast batches of kimchi to last the winter. The lactic acid bacteria that fermented the cabbage didn’t just preserve it—they made it safer, more nutritious, and less hospitable to harmful microbes. Fermentation was often paired with salt or acid, both of which further protected it. In German and Scandinavian households, sauerkraut filled that same role—an acidic, shelf-stable winter staple that kept scurvy at bay and maintained gut health during long stretches without fresh produce.

Eastern European winter rituals often included kefir, skyr, or other cultured dairy foods. These are packed with probiotic organisms that support gut immunity, which is especially important in winter when respiratory infections are common and diets narrow. In many parts of the Middle East and Central Asia, fermented yogurts and ayran were central to winter meals because they remained safe even when milk supplies were precarious or storage conditions were unreliable. In Japan, fermented pickles (tsukemono) provided vitamins and beneficial bacteria during the Shōgatsu New Year celebrations. And in Mexico and Central America, lightly fermented holiday drinks like tepache added safe hydration at a time when stored water wasn’t always trustworthy.

Across all these cultures, fermentation wasn’t just about survival; it was about creating food that nourished the body in ways people didn’t fully understand yet. Lower acidity meant fewer foodborne pathogens. Lactic acid bacteria protected the gut and, indirectly, the immune system. And fermented foods allowed communities to store harvests through the dark months without relying on freezing or refrigeration. No germ theory needed—just centuries of observation that certain foods kept families healthy through the winter, and so those foods became woven into holiday rituals.

But food is only part of the story.

Across cultures, winter holidays are tied to cleaning, renewal, and preparing the home for a season when people were about to spend much more time indoors. In Japan, the deep-cleaning ritual of Ōsōji marks the transition into the New Year. Families scrub floors, wash walls, shake out bedding, and clear clutter so the home begins January fresh and orderly. Today it’s symbolic, but historically it removed dust, mold spores, soot, and insect debris at precisely the moment when closed homes and poor ventilation could turn those irritants into health hazards.

In Jewish households, pre-holiday cleaning has long-standing spiritual meaning, but it also had incredibly practical benefits. Burning crumbs of old bread or removing stored grains before major winter holidays reduced the chances of rodents settling in for the season—and rodents were major vectors for disease long before anyone knew the biology behind it.

Many European families prepared for Advent with a top-to-bottom scrub-down of homes, linens, ovens, and hearth spaces. This wasn’t just aesthetic. In smoky, drafty cottages heated by wood fires, soot accumulation created respiratory problems, and damp winter air encouraged mold. A pre-Advent cleaning helped reset the environment before months of indoor living.

In Persia, winter solstice traditions around Shab-e Yalda also included preparing the home and checking food stores: sorting nuts and dried fruits, cleaning hearths, and removing anything that might spoil or attract insects during the cold months. These preparations reduced the risk of foodborne illness right when supplies were tightest and meals were most communal.

And versions of this existed everywhere. In parts of sub-Saharan Africa, winter festival periods included sweeping compounds and refreshing earthen floors with new clay or ash—materials that reduce microbial growth. In China and Vietnam, pre-Lunar New Year cleaning cleared away dust and pests before winter feasting began. Even European “whitewashing day” traditions—painting fresh lime over interior walls in late fall—had hidden benefits: limewash is mildly alkaline and naturally antimicrobial.

None of these were designed as infection-control protocols, but they functioned like them. They removed vector attractants, kept indoor air cleaner, reduced allergen loads, and made winter homes less hospitable to pathogens at exactly the moment when people were clustering inside to stay warm.

Light is part of the story too. Candles, bonfires, and lantern festivals were central to winter holiday traditions across Europe, South Asia, the Middle East, and the Americas, not just because they were beautiful, but because people instinctively reached for light and warmth in the darkest months. Yule logs burned through the longest nights in Northern Europe. Hanukkah menorahs glowed in windows. Diwali lamps illuminated homes across India during festivals that sometimes overlapped with the cooler season. In Mexico and Central America, posada processions carried candles through the streets. And in East Asia, winter lantern festivals turned entire towns into seas of flickering light.

The warmth and smoke of these fires had side benefits. Smoke helped deter insects—mosquitoes and flies in warmer regions, and fleas and other pests in colder climates. Heat created convection currents that pulled fresh air in through cracks and pushed stale air up chimneys or out open doors. This meant many winter homes had far more airflow than modern, tightly sealed houses. A crackling fire was essentially a primitive air-exchange system, constantly pulling in new air and pushing out smoky, microbe-laden air. Today we talk about air changes per hour; back then, people just called it “keeping the fire going.

Winter kitchens amplified this effect. When bread was baking, when pots simmered on the stove, or when a family prepared a holiday feast, windows had to be cracked open to release steam and smoke, even when the weather outside was frigid. Kerosene lamps, wood stoves, indoor braziers, and open hearths all pulled air upward and outward. Unlike today’s tightly sealed homes, those spaces breathed—air flowed through cracks, chimneys, and doors, thinning out airborne pathogens at exactly the moment respiratory infections peaked. Of course, wood smoke is also an irritant, especially in poorly ventilated homes. But where airflow was decent, the ventilation benefits often outweighed the downsides.

Social traditions played their part too. In much of Europe and North America, winter historically meant staying put. Roads iced over, rivers froze, and travel was slow, risky, or simply impossible. Families celebrated in small groups because distance and weather made it so. Before trains, cars, and airplanes, winter holidays were hyper-local rituals. And unlike Lunar New Year, which has always involved enormous migrations across Asia and is known for its annual surge in illness, Christmas in the pre-modern world often kept communities near home—meaning fewer mass gatherings, fewer strangers sharing indoor air, and fewer opportunities for respiratory viruses to spread. Of course, some religious observances still brought people indoors—like Christmas Eve masses—but many communal activities, like processions or feasts, remained local or even outdoor whenever weather allowed.

Even the traditions that brought people together often happened outdoors. Caroling wasn’t a cozy indoor sing-along; it was an outdoor ritual, with groups of people singing in the cold where ventilation was perfect and viral transmission was low. Nordic “Julbock” parades, St. Lucia processions in Scandinavia, and Christmas Eve bonfire traditions in parts of France and Appalachia were all outdoor gatherings that allowed people to socialize in the safest possible environment without anyone understanding why it was safer.

These rituals weren’t designed as public health measures—but they worked like them, reducing indoor crowding, increasing fresh-air exchange, and creating winter social patterns that unintentionally protected communities long before germ theory existed.

And yet we still have a winter cold and flu season. Every year.

So if all these traditions were helpful, why does it feel like winter viruses dominate our lives now?

Because winter itself is the real driver—and today’s world amplifies everything those viruses need.

Respiratory viruses like influenza, RSV, and seasonal coronaviruses thrive in cold, dry air. Low humidity makes the droplets we breathe stay airborne longer. Cold temperatures weaken the immune defenses in our noses. Short days reduce vitamin D levels. People crowd indoors with windows shut tight. And modern homes, sealed for energy efficiency, trap viral particles in the air.

Then add the modern world: eight billion people, dense cities, crowded schools, international flights, holiday travel surges, packed shopping centers, office parties, concerts, reunions, airport security lines, and year-round global circulation of viruses. Even the traditions we still practice—like caroling, holiday dinners, and candlelight services—often happen indoors now in tightly sealed spaces that don’t allow the natural ventilation our ancestors relied on without thinking.

In other words, winter viruses have the advantage—biology, climate, and global population dynamics are working in their favor. Holiday traditions once gave us small, accidental boosts, but in a world this connected, they can’t outweigh the fundamental physics of cold air and the sheer number of people sharing it.

Still, the story is worth telling—not just as history, but as a reminder of how humans have always adapted to the season. People saw darkness and lit candles. They felt the cold and turned to spices, fermentation, and evergreens. They hung resinous branches that released antimicrobial scents, cooked foods that nourished their communities, and passed down rituals that made the hardest season survivable.

Some of those traditions helped in ways they never realized. And today, knowing the science, we can see the quiet wisdom in these practices: the emphasis on warmth, air, nourishment, and togetherness—even when togetherness looked different than it does now.

Humans have always been inventing rituals to make winter safer, even without germ theory. We still do. And there’s something comforting in knowing that many of the things we love about the holiday season carry echoes of ancient ways of staying well.

And while we no longer rely solely on these old-school traditions for survival, some of them are worth bringing back in small, modern ways—not because they’ll prevent winter viruses entirely, but because they can gently tip the odds in our favor. Opening a window for even a few minutes while baking or hosting guests can refresh the air without losing too much heat. Using spices like clove, ginger, and cinnamon in winter cooking adds cozy flavor while echoing their ancient antimicrobial roles. Bringing evergreen branches indoors isn’t just decorative; their natural resins lightly freshen the air. Taking a brief walk outside with friends instead of always gathering indoors, lighting candles for ambiance while keeping a bit of airflow moving, and clearing out old pantry items during pre-holiday tidying are all traditions with quiet, practical benefits. None of these are cures—but they’re small, thoughtful ways of reconnecting with the winter wisdom our ancestors built into the season.

And here’s the modern twist: these little practices are meaningful, but they cannot replace the major tools we have today—vaccines, high-quality masks, and smart ventilation. The need for evidence-based protection is more urgent than ever. In November 2025, the Department of Health and Human Services, under the leadership of Robert F. Kennedy Jr., removed the statement that ‘vaccines do not cause autism’ from its vaccine safety communications. This was not a correction based on new evidence — the science has been clear for decades that there is no link. It was a political decision driven by ideology, not research. For everything you need to know about how we know vaccines do not cause autism, see my episode on the subject. I provide all the evidence. Changes like this do not reflect the evidence; they reflect a dangerous erosion of public trust. So while we embrace the winter rituals that once protected us, we must pair them with the clearest tools we have today: real science, honest messaging, and the courage to speak plainly in the face of distortion.

Because the truth is, wisdom doesn’t always look like a white coat or a lab bench. Sometimes, it smells like cinnamon, sounds like singing, or glows from a lantern in the dark. And when paired with science, those old instincts still have something to teach us.

Thanks for being here! Join us next week for a new vaccine safety episode. Until then, stay healthy, stay informed, and spread knowledge not diseases.

References

1. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews 2013, Issue 1. Art. No.: CD000980. DOI: 10.1002/14651858.CD000980.pub4.

2. Tajkarimi, M.M., Ibrahim, S.A. and Cliver, D.O. (2010) Antimicrobial Herb and Spice Compounds in Food. Food Control, 21, 1199-1218.

   https://doi.org/10.1016/j.foodcont.2010.02.003

3. Marco, M.L. et al. (2017). Health benefits of fermented foods: microbiota and beyond. Current Opinion in Biotechnology, 44, 94–102.

4. Steinkraus, K.H. (1997) Classification of Fermented Foods: Worldwide Review of Household Fermentation Techniques. Food Control, 8, 311-317.

   https://doi.org/10.1016/S0956-7135(97)00050-9

5. Sundell, J. (2004). On the history of indoor air quality and health. Indoor Air, 14(Suppl 7), 51–58. https://doi.org/10.1111/j.1600-0668.2004.00273.x

6. Milton, D.K., Glencross, P.M., & Walters, M.D. (2000). Risk of sick leave associated with outdoor air supply rate, humidification, and occupant complaints. Indoor Air, 10(4), 212–221.

7. Moriyama, M., Hugentobler, W.J., & Iwasaki, A. (2020). Seasonality of respiratory viral infections. Annual Review of Virology, 7(1), 83–101.

8. Jones, D.S. (2020). History in a Crisis — Lessons for Covid-19. New England Journal of Medicine, 382(18), 1681–1683.

9. Guarner, F., & Malagelada, J.R. (2003). Gut flora in health and disease. The Lancet, 361(9356), 512–519.

10. McGee, H. (2004). On Food and Cooking: The Science and Lore of the Kitchen.