While cold weather itself does not cause illness, sudden temperature drops and dry air can weaken your body's defence against pathogens. This makes you vulnerable to infections such as colds and flu. When it comes to illnesses, particularly seasonal ones, the nose is your first line of defence against airborne irritants and pathogens. Both nasal passages have an internal humidification system that adapts to external conditions. However, dry air—typical of winter conditions—forces the nose to work harder to humidify the air, which in turn compromises its ability to filter out viruses and bacteria.Mucus Is The Protective Layer In NoseThe nasal mucus layer acts as a protective barrier, capturing harmful particles before they reach the lower respiratory system. When viruses or bacteria invade, cells in the nose release decoy extracellular vesicles (EVs) to trap the pathogens. However, cold air reduces the temperature inside the nose, killing nearly half of the virus-fighting cells. This, combined with low humidity during colder months, can significantly impair the nose’s defences. Flu season, typically from October to May, and cold season, from late August to March, coincide with these environmental changes.Beyond weather, there are other factors that can lead to your nose getting dry. These include dehydration, frequent nose-picking, allergies, certain medications, and exposure to tobacco smoke or scented products like candles and air fresheners. Notably, a person experiencing nasal dryness would experience symptoms like soreness, irritation, thick or crusted mucus, nosebleeds, and an altered sense of smell. How Can You Optimise Your Nasal Defence?Experts recommend maintaining indoor humidity levels between 35% and 45% to keep nasal passages functioning properly. A humidifier can help. This device increases the humidity in the air by releasing steam or water vapour. However, it has a major drawback. As per experts, excess humidity leads to mould, which can cause infections, increase asthma attacks, and cause allergies. Ensuring appropriate humidity indoors is the key to strengthening your nasal defences and preventing illness in colder months. Despite following the precautions, if you get sick, should you spit your mucus out? Absolutely Yes! Excess mucus, whether in your throat or your lungs should be spit out. Most doctors too agree with this. While mucus does protect you, the one that is produced when you are sick is filled with irritants, allergens, and infectious organisms that must be cleared from the body. Doctors also recommend spitting it out to open up the drainage pathways of your nose and sinuses.While there are some notions that suggest that swallowing a cough could harm your stomach or intestines, doctors say that there are no such evidence for this. Experts suggest that even if you swallow your mucus, it gets eliminated through the gastrointestinal tract. This means our GI tract breaks the mucus down, and we eventually excrete it. While spitting out mucus can make us feel better in the moment, on average, we swallow mucus all day, all of this gets broken down in our gastrointestinal tract.