Why your cosy Christmas home might be triggering health issues (and how to fix it)

A functional medicine perspective on indoor air quality, fine dust, & why you actually need to go outside this holiday season.

As the days grow shorter and the festive lights start twinkling, I feel that familiar pull to hibernate. We all do. There is something deeply primal about retreating indoors, wrapping ourselves in blankets, and lighting a candle against the dark.

But as someone who has spent 18 years in medicine—and as a physician who understands the tightness of a chest struggling for air—I need to have an honest, heart-to-heart conversation with you about what is happening inside our homes this winter. We tend to view our homes as sanctuaries, especially during the holidays. However, for those of us navigating asthma, autoimmunity, or respiratory sensitivities, the "most wonderful time of the year" often brings a hidden cocktail of triggers.

We typically think of pollution as something that happens outside, involving factories and traffic. But the science tells us a different story: our well-insulated, cosy homes can sometimes be the most toxic environments we encounter. Let’s unpack this together, looking at the root causes, and I promise to give you practical, holistic tools to breathe easier and lower inflammation this Christmas.

The "sealed box" syndrome

In our effort to be energy-efficient, we have become experts at sealing our homes. We install double-glazing and block drafts to keep the heat in. However, without active ventilation, we are effectively living in a "sealed box." When we cook, clean, or even just breathe, we generate pollutants. In summer, these escape through open windows. In winter, they stay. They accumulate.

Have you ever woken up in winter with a headache, or felt sluggish and "heavy" after a family gathering? We often blame the heavy food or the wine, but frequently, the culprit is Carbon Dioxide (CO2).

Outdoors, CO2 levels sit around 400 parts per million (ppm). In a sealed bedroom or a busy living room, levels can easily spike above 2,000 ppm. Research indicates that at these levels, we see statistically significant decrements in decision-making performance. For those of us with sensitive airways, high CO2 acts as a stressor. It can stimulate our respiratory drive, making us feel like we can't get a deep enough breath—a sensation often called "air hunger" that can mimic or trigger anxiety and asthma symptoms.

My tip: Invest in a simple CO2 monitor. It’s an eye-opener. When it hits 1,000 ppm, it’s time to ventilate.

The Christmas combustion cocktail

Here is where we need to talk about particulate matter (PM). These are tiny particles suspended in the air. We generally look at two types:

• PM10: Coarse particles like dust and mould spores. They irritate the nose and throat.
• PM2.5: Fine particles. These are the troublemakers. They are small enough to travel deep into the lungs and enter the bloodstream, potentially driving systemic inflammation.

During the holidays, we unwittingly create a spike in PM2.5 that I call the "Christmas Combustion Effect."

1. Candles: I adore the glow of a candle, but burning paraffin releases soot and volatile organic compounds (VOCs). It is essentially a small engine running in your living room. Studies have shown that candle burning contributes significantly to personal exposure to potentially hazardous particulate matter. Scented candles can be even more problematic, releasing chemicals like limonene which can react with ozone in the air to form formaldehyde.

2. Wood burners: There is nothing more romantic than a wood fire, but wood smoke is a potent respiratory irritant. Even opening the stove door to add a log can cause a massive spike (up to 400%) in indoor PM2.5 levels.

3. Cooking: Roasting that delicious holiday feast releases aerosolized fats and combustion byproducts. If your extraction fan isn't powerful (or if you don't use it because it's noisy), those particles settle deep in your lungs.

Why you must go outside (yes, even now)

I often hear my patients say, "Dr. Naomi, I can't go out, the cold air hurts my lungs." I hear you. Cold, dry air can cause what we call "osmotic shock" in the airways—drying them out and triggering a spasm. Cold air can cause airways to narrow, increasing mucus production and making it harder to breathe.

However, staying indoors 24/7 deprives you of a critical immune booster: Shinrin-yoku, or Forest Bathing.

Originating in Japan, Shinrin-yoku isn't just a walk; it is medicine. Trees, particularly conifers (like our Christmas trees!), release compounds called phytoncides. Research shows that inhaling these compounds boosts our Natural Killer (NK) cells—the soldiers of our immune system that fight off viruses. Furthermore, nature lowers cortisol (stress hormone) levels. Since stress is a major trigger for inflammation and autoimmune flare-ups, a walk in the woods is essentially an anti-inflammatory intervention.

How to do it safely: We don't want you to freeze your lungs. We want you to condition them.

• The Scarf Technique: Loosely wrap a scarf over your nose and mouth. This creates a pocket of warm, humid air, so you aren't shocking your bronchial tubes with freezing air.
• Check the AQI: Before you go, check the Air Quality Index.
  • 0–50 (Green): Go enjoy the forest!
  • 101–150 (Orange): Sensitive groups (that’s us) should take it easy.
  • >150 (Red): Stay inside and activate your "clean room" protocols.

Nutritional armour for your lungs

As an integrative physician, I believe we can use food to build resilience against pollution. We can't always control the air, but we can control how our body responds to it. New nutritional research suggests that certain nutrients can mitigate the damage caused by PM2.5 exposure:

• Omega-3 Fatty Acids: Found in oily fish, walnuts, and flaxseeds. These dampen the inflammatory response in the lungs.
• Vitamin C: A powerful antioxidant. Studies suggest it helps protect lung tissue from oxidative stress.
• Sulforaphane: Found in broccoli and cruciferous vegetables. It supports the body’s detoxification pathways.

Frequently Asked Questions (FAQ)

I receive these questions constantly in my clinic, so I wanted to share them with you.

Q: Can I use my HEPA vacuum to clean my indoor air? A: No, please don’t rely on this! This is a very common myth. While a vacuum with a HEPA filter is great for trapping what it picks up from the floor, the exhaust from the vacuum motor creates turbulence. This often kicks up settled dust from the rest of the room, creating a "dust cloud" that can linger. Vacuuming is for surfaces; for the air, you need a dedicated air purifier.

Q: Should I use a humidifier or an air purifier? A: They do different jobs. An air purifier removes dust, allergens, and smoke—this is your lung protector. A humidifier adds moisture. Winter air is dry, which dries out your mucus membranes (your first line of defence). However, be careful—if humidity goes above 50%, dust mites and mould love it. Aim for 30–50% humidity.

Q: Is it safe to open windows in winter? A: Yes! In fact, it is necessary to flush out that CO2 and viral load. The trick is the German technique of Stosslüften (shock ventilation). Instead of leaving a window cracked all day (which cools the walls and wastes energy), open everything wide for 5 to 10 minutes. The air is exchanged completely, but the furniture and walls keep their heat. This simple habit significantly improves indoor air quality.

Q: What does the AQI score actually mean for me? A: The Air Quality Index is your daily forecast for lung health. It tracks pollutants like ozone and particles. If you have asthma, pay attention when it shifts from Yellow (Moderate) to Orange (Unhealthy for Sensitive Groups). That is your signal to prioritize indoor activities or wear a mask if you must be out. You can learn more about specific AQI ranges here.

My Invitation to You

This winter, I invite you to create a sanctuary that is truly safe. Swap that paraffin candle for a beeswax one (or a lovely battery-operated glow). Ventilate your home with intention. Wrap up warm with your scarf and go find a tree to breathe with.

Your lungs are precious, and with a few gentle tweaks, you can navigate this season with vitality.

Does this resonate with you? Do you notice a change in your breathing when you’re indoors versus outdoors? I would love to hear your story in the comments below. Together, we’re making the journey to true health a little brighter!

With warmth and health,

Dr. Naomi