Many of us can fall ill every now and then, but it can feel especially common during the winter months. So why do we generally feel more under the weather throughout the winter? We’ve dug out the top 5 reasons you might be feeling sub-optimal;


1. Low Vitamin D Levels

During the winter, we get much less sunshine and don’t tend to volunteer for more time outside. This reduction in sunlight also means or bodies produce less vitamin D.

You’ve probably heard by now just how important vitamin D is in for our general health. It’s vital for keeping our bones healthy and is also used in the modulation of innate and adaptive immune responses [1]. If vitamin D is a key to modulating our immune responses, it follows that lower levels of vitamin D would then negatively affect our immune system.

It’s also worth noting that there’s a link between low levels of vitamin D and symptoms of depression. But the research isn’t conclusive yet as to whether depression caused by or affects vitamin D levels [2].

People living in the northern hemisphere are at a higher risk of vitamin D deficiency, according to a 2008 study [3]. So that risk is doubled come wintertime. It’s recommended that those living in northern latitudes supplement vitamin D as a precautionary method.


2. Seasonal Affective Disorder

Seasonal affective disorder is a kind of depression that is brought on by the time of year (most commonly winter). Now, we did mention depression briefly earlier – but it deserves its own section in this list because of how much it impacts our wellbeing.

Those with depression can expect lowered energy levels, mood and immunity. In fact, even mild depression can harm our immunity according to a study in 2003 [4].

Stress and depression are both known to cause a rise in inflammatory factors, which can increase your risk for several health conditions. This effect on your body all adds up to leaving you tired, lethargic and generally feeling unwell. You’re also more susceptible to a passing cold with depression.


3. Less time in nature/outside

NatureNow, winter isn’t known for being the season of enjoying leisurely strolls or garden parties, we all spend much less time outdoors in the colder months compared to the rest of the year. You’d expect it to be harmless – Afterall, going outside into the cold isn’t exactly comfortable. But all that time indoors might be what’s making you feel under the weather.

There’s been a fair bit of research on the effects of being outside on both our mental and physical wellbeing and the general consensus is that it’s highly beneficial for our vitality [5]. We’re meant to be outdoors and hence, taking a 15-minute walk in the park is both a great way to get some exercise in and improve your mood. Walking outdoors is also believed to improve cognitive function- as it promotes blood flow.


4. Seasonal Allergies

Not many people realise that seasonal allergies aren’t exclusive to spring and summer. Different allergies can be brought on in different seasons. There are a few factors that come into this;

Firstly, there are different pollens around during winter – there isn’t suddenly a complete absence of pollens, but the pollen count is usually lower than during the warmer months, which is why it isn’t usually on our radar.

Secondly, a more common allergy that’s more prevalent in the winter is a dust mite allergy. Due to a combination of us spending more time indoors and keeping windows and doors shut to stay warm, those with an allergy to dust mites will experience an influx of symptoms over the winter.

Closing off all exits can help us to stay warm, but it also stops air from circulating and can cause a build-up of dust mites in your house if this happens those you can expect a runny nose, itchy eyes and congestion to be among your symptoms.

These symptoms can often feel similar to those of a cold or flu, so many people may not realise that the reason they’re feeling a bit ill actually because of the increase in dust mites.


5. Winter Flu

Finally, we had to include the default answer to why you may be feeling under the weather in the winter. Seasonal flu and passing colds are much more common throughout winter as we spend more time huddled together in confined spaces where germs are nigh impossible to avoid.

While it isn’t the only potential cause of your sluggishness, fatigue or congestion, it’s high on the list of most likely causes.

There are several reasons you might be feeling under the weather, and it can feel like quite a task to figure out which one of these is the cause for you, you can at least eliminate the question of allergies with a home-to-lab allergy test.

Taking an at-home allergy test can take out the guesswork and even identify other potential allergies you might not be aware of. It can certainly offer a benefit if self-care hasn’t helped, and your symptoms seem to be lingering.



[1] Aranow, C. (2011). Vitamin D and the Immune System. Journal of Investigative Medicine, [online] 59(6), pp.881–886. Available at: [Accessed 19 Feb. 2020].

[2] Cuomo, A., Giordano, N., Goracci, A. and Fagiolini, A. (2017). Depression and Vitamin D Deficiency: Causality, Assessment, and Clinical Practice Implications. Neuropsychiatry, [online] 07(05). Available at: [Accessed 19 Feb. 2020].

‌[3] Huotari, A. and Herzig, K.-H. (2008). Vitamin D and living in northern latitudes–an endemic risk area for vitamin D deficiency. International journal of circumpolar health, [online] 67(2–3), pp.164–78. Available at: [Accessed 19 Feb. 2020].

[4] Jeanie Lerche Davis (2003). Even Mild Depression Harms Immunity. [online] WebMD. Available at: [Accessed 19 Feb. 2020].

[5] Ryan, R.M., Weinstein, N., Bernstein, J., Brown, K.W., Mistretta, L. and Gagné, M. (2010). Vitalizing effects of being outdoors and in nature. Journal of Environmental Psychology, 30(2), pp.159–168. Available at: [Accessed 19 Feb. 2020].