Why the Holiday Season hurts your immune system

Have you ever wondered why it seems like everyone gets sick from November into February?

There are a lot of different ideas that get thrown around, but today I want to look at some of the specific ways we unknowingly lower our immune system, starting with the end of October.

Not all of these will apply to everyone, but then, not everyone gets sick every year.

Almost everything that lowers our immune system is connected to increased levels of chronic stress. Your response to stress impacts every organ in our body, so it should not be a surprise that it affects your immune system, too. The list below is about the different sources of stress that impact us during the holiday season, starting with weather. While weather is not within our control, and it is heavily dependent on the latitude where you live, there are a lot of things about it that we can control.


  • Reduced sunshine exposure

From approximately September 22 to March 22 we are in the darkest half of the year, with the shortest amount of sunshine occurring in mid-December on the Winter Solstice. This fact alone reduces the amount of sunshine possible that you can be exposed to, but there are other factors that exacerbate this fact.

First, most people avoid going out in the cold for extended periods of time. One thing that I have noticed is that as people spend more time indoors with efficient climate control, they lose their tolerance for temperature changes – myself included. You see this in the summer and in the winter. This further reduces time out in the sun. To compensate for the cold, people also bundle themselves up, which is the second factor in reducing exposure to sunshine.

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Because vitamin D is created when sunlight falls on your skin, having 95+% of your body wrapped up eliminates most of the benefit you would receive from going outdoors. The general recommendation is to get 15 minutes of sun each day, but with so little exposed skin, it would take much longer to get enough sunshine to produce adequate vitamin D to support your immune system. Also, most windows now block all or some of the UV rays that are required to produce vitamin D, so while you will get a mood-boost from being near a window, it will not contribute to your vitamin D levels in a significant way.

  • Mucus membranes impacted by artificial heat / dry air

A secondary effect of the colder temperature, is a natural reduction in the moisture in the air. When the air is then heated, the relative humidity of the air drops, and this leads to dried out sinuses. Our mucus membranes are actually a first line of defense for our immune system, so when they are dried out, it opens a door for germs and bacteria to enter our system without setting off alarms.

  • Exposure to sudden and wide temperature swings

The next challenge is our exposure to sudden and wide temperature swings. When it is in the 30s and below outside but in the 60s and 70s inside, going from the house to the car, from the car to the store, etc, exposes you to short and sudden temperature swings. Plus, with the heater in the car, you are either dressed for the cold and get overheated, or you are dressed for the indoors and get chilled. This is a significant stress to your body and when coupled with all the other challenges to our immune system, can be overwhelming.

  • Extended exposure to cold without sufficient activity levels

The final challenge I want to mention is improper cold exposure. The research continues to show how healthful cold exposure can be, but there are definitely wrong ways to do it. Mainly, your immune system is down-regulated if you just stand out in the cold – instead, the benefit seems to correspond with activity level and generated body heat. If you are moving enough to break a sweat, then you will experience an increased immune system.

Now, because much of the above depends on things outside of our control, you can get vitamin D through your diet – particularly through fatty fish, pasture-raised eggs, and grass-fed beef liver.

The next category of immune-impacting stress I want to look at is our time in the holiday season:


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  • Shopping

For those of us who get overwhelmed by large crowds, shopping during the holiday season is a real stress. This is on top of simply finding time to actually get to the store.

  • Parties

For my family, our busy social season typically begins in October and ends around New Year’s Eve. Between the events that are being hosted before the holidays, then all the holiday parties you might be invited to, it gets really crowded really quick. There are so many events and only so much you.

  • Travel

Then, if you are going to see family very far away, or just taking time off of work, coordinating that schedule can be a head-ache.

  • Work

And on top of all the holiday-related events, most of us still have to work most of that time. Plus, there is all the work-specific stress that can occur in the Holidays. That has its own section below.

  • Not enough rest scheduled

Between all those demands on our schedule, it is really easy to quickly lose all your down-time, your recharge moments. It is important to be realistic about what events are going to be enjoyable, but not restful. I know I have tended to fool myself into the idea that because it is enjoyable that it will be restful. It usually isn’t for me. It’s important to make time for rest and play in the middle of everything else – it will give your immune system a huge boost from all the stress induced from an over-packed schedule.

Beyond just the schedule-induced stress, each one of those items above brings other stress. First we are going to tackle travel:


  • Exposure to more/different germs / bacteria

Our immune system isn’t like anti-virus software that gets regular updates based on what’s happening around the world. It is very specific to us and our environment. When we travel, we get exposure to all new cocktails of bacteria and viruses that our immune system may not be prepped to handle. Thankfully, our immune system is constantly learning, so if this is the only challenge it should be up for it, however, there are a lot of other damaging things that occur while traveling.

  • Stress over schedule

For me, I am a very time-oriented person, and delays cause me a significant amount of stress and anxiety. If you are worried about making a flight, or getting somewhere in time for supper, or getting in before the storm, this is a low-level chronic stress about something that may be outside of your control, and really provides no benefit to your life. This is the worst kind of stress for your immune system.

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  • Limited food choices

Then, once you are traveling, you are often limited in your food choices compared to when you are at home. If you are road-tripping, then you often get more fast-food, and maybe even a smaller selection of that than you are used to. If you are flying, then you might be stuck with airport food, which is not always terrible, but it is a smaller selection than if you are driving around town. Then, once you get to your destination, you are likely eating whatever is served, which may or may not agree very well with you. All this can stress your digestive system, and most of your immune cells are in your digestive system at any given time.

  • Often involves increased coffee consumption

If you are blessed with the chance to take time off work and go travel, you are likely trying to make the most of your time, so that often means heading out early in the morning or later in the evening. Either way, this can often lead to drinking more coffee, soda, or energy drinks in an attempt to avoid being drowsy. Beyond the caffeine, these will typically also displace your water consumption.

  • Impacted workouts/skipped workouts

Between the hit-or-miss hotel gyms, trying to make the travel time short, and having two little kids, I rarely get a real workout in while I’m on the road. Then, once I’m at my destination, we generally have things scheduled such that workouts are either just to get the fluids pumping a little or they just don’t happen. Done correctly, a good workout will improve your immune system. Done wrong, or even not done at all, will have several affects that impact your immune system.

  • Impacted sleep

Once you add up all the issues above, plus sleeping in a different space, you always get impacted sleep, and this is one of the worst things for your immune system. When you sleep is your body’s time for maintenance. Rest and food are the two most powerful tools available for improving your health. What you eat also has a direct effect on your sleep – either helpful or hurtful.


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  • Increase in sweets/desserts

Starting with Halloween we tend to have an increase in candy, sweets, and desserts. It has become part of the holiday season. It is hard to avoid so much of it, too, between family, holiday parties, gifts of food, and break room treats. Sugar has a cascade of effects, including lowering your immune system.

  • For some, increase in alcohol consumption from holiday parties

Besides sugar, alcohol also lowers your immune system. Holiday parties often have spiked eggnog or bars and can lead to significant drinking. If someone at the party was not feeling well, you may spend a significant amount of time with them while also compromising your body’s ability to resist the bacteria or virus. Plus, when you are at a party you have fewer options available for your food, increasing the likelihood of eating food your are sensitive to.

  • Potential for increased exposure to food sensitivities

Food allergies used to get all the press, but people have become so much more aware of foods that don’t provoke an allergic reaction but still cause side-effects from consumption. This can be a response by part of the immune system, an inability to digest certain foods, or just an imbalance in your gut bacteria. Frustratingly, these sensitivities can be to common ingredients. When you are a guest somewhere, it becomes difficult to control food selection, and also portion sizes.

  • Eating more food, or foods you should avoid, simply to please family/host.

For many people, the idea of turning down food that has been offered to you is the height of rudeness. Instead, people will eat food they don’t want or shouldn’t eat simply to be polite. We have been conditioned to protect other’s feelings at the cost of our own health.

  • Impacted eating schedules

Beyond the amount or type of food, we can also get derailed by trying to adjust our eating schedule to meet someone else’s expectations. Especially on big days like Thanksgiving or Christmas, breakfast can get left behind in the preparations for the big meal of the day. If you are adjusted to that, great! If you are used to eating a big hearty breakfast to prepare you for the day, this can throw your blood-sugar off for quite awhile.

  • Eating while stressed

Finally, one of the worst things you can do is try and eat a large meal while stressed. When we are stressed, our digestion gets reduced as non-essential for our immediate survival. This means that the turkey, two kinds of dressing, and three kinds of pie just sit in your intestine, adding another source of stress to your body and further impacting your immune system.


  • Stress over family gatherings

As great as it can be to get together with the whole family, it can also become a huge stressor. Trying to organize dates and times, travel, lodging, etc, it can quickly get out of hand. Not to mention that most families are dysfunctional in some way, and that there is almost always some kind of tension between family members.

  • Sadness from missing family

Or maybe the stress is because you can’t make it to the family gathering this year. Or you are sad over the family that won’t ever be there again. I struggle with this every December, even though it’s been 10 years since my grandmother died and longer still since my grandfather died. Christmas and Thanksgiving were always spent with them, and now that they are gone I struggle every holiday season.

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  • Dissonance between holiday ideal and reality

And part of that struggle is facing the gap between what I imagine the holiday should be like and what it really is. To me, the holidays should be about slowing down and enjoying time with family, but instead it seems as though it is the busiest time of the year. It doesn’t really matter what the disconnect is about, the stress comes from there being a disconnect. For a lot of people, this disconnect can be caused by the gifts we want to buy our family versus what we can find and afford.

  • Stress about gift giving/finances

Gift giving seems to be a strength for some, but is typically a struggle for me. Part of that is simply trying to find meaningful gifts for everyone that they will appreciate, and not just become something else gathering dust on the shelf. The other side is how much gift you can afford to give everyone. For most of us, we don’t have an unlimited budget at Christmas, and financial stress can be one of the most deeply felt, as it impacts our basic needs: food and shelter.


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  • Deadlines

How your job is during the holidays is highly varied. For some people, work slows way down, for others it is the busiest time of the year. For many companies, there is a drive to finish projects and tasks before the end of the year. This gets compounded when you are trying to get everything wrapped up before the holiday party, or your Christmas vacation. Trying to get it all done can often lead to working overtime, which brings complications.

  • Overtime

Whether you are working overtime trying to get everything wrapped up at work before taking time off, or because your company is so busy during the holiday season that you are required to work extra, it can easily derail your attempts at taking care of yourself. Getting good sleep, eating good food, and good workouts can seem like luxuries when you are busy at work, and yet the busier you are, the more important they become. Then, when you are running low on energy, you are more tempted to grab the donuts in the break room.

  • More treats in the office

Because during the holiday season, everyone seems to bring in more donuts, more cookies, more cake, more candy. If it isn’t coworkers, it can be companies that your company does work with sending gift baskets. Because lack of sleep causes our cortisol levels to rise, we naturally turn to sugary foods to keep our energy (and our stress) up through the day until we feel safe getting to bed. Of course, being the holiday season, there is usually a Christmas party hosted by your work.

  • Work Christmas parties

There is usually an implied obligation to attend the office party. But unlike parties with friends, you are typically aware that what happens at the party can impact your future at that company, leading to increased stress. With increased stress comes a desire for sugary foods, and often a turn to alcohol to take the edge off so you can enjoy yourself. Alcohol has been shown to impact your immune system. So now you are in a crowd with some level of stress or anxiety, drinking alcohol, eating foods that probably aren’t on anyone’s regular diet, and enjoying dessert, lowering your immune system while potentially exposing yourself to viruses or bacteria that your body has not been recently exposed to.

  • Worry over job future

Finally, many companies do performance reviews around the end of the year, often coupled with end-of-year bonuses. These always bring some anxiety, as the generosity of your bonus can make or break your holiday gift-giving. If you’ve been working a seasonal job, then there can be trepidation about what the new year will bring, since you are practically guaranteed that your current job will end. Again, the is just another source of chronic stress, and chronic stress lowers our immune system, opening us up to getting sick. Of course, the stressors don’t end with Christmas, they continue on, starting with our New Year’s Resolutions.

New Year’s Resolution

Some of the more popular New Year’s Resolutions are lose weight and exercise more. Both of these are admirable, but often the attempt to achieve them is unrealistic.

  • Over-stressing a tired body

We get obsessed over what can we DO to improve, we forget that adding more things just results in greater stress to our system. The first place to look is to see what we can STOP doing. What is the one thing that we are currently doing that has the worst impact on our health or time? Instead, we immediately turn to things that further clutter our schedule without considering what will have to be displaced.

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  • Picking unhealthy ways to achieve goals

Usually the first way people try to lose weight is to go on a calorie-restrictive diet. This automatically signals to your body that there is not enough food, so it needs to have a stress-response so that you will have the focus and energy to find more food. Additionally, if you have restricted too many calories, your body will down-shift your metabolism to need less food, and then use the “excess” calories to store as fat in case food disappears completely.

Second, people usually pick an unrealistic goal for exercising more. You look at people like The Rock, and his workouts, but most people don’t recognize that it has taken years for him to get his body where it is. This isn’t just the size of the weights, but the amount of work and the length of his workouts. You can’t go from exercising 20 minutes a week to exercising an hour every day just because you want to – your body needs time to adapt. By over-exercising you are breaking down your body, including your immune system, more than it can recover from, leaving you more vulnerable to the flu and other contagious diseases.

  • Binges

Once we start these unrealistic attempts to achieve our goals, and fail, it often leads to a binge – over-eating, or spending all weekend watching movies or shows. The bounce is usually pretty rough. Because we have not allowed room on our course of action for missteps we see any mistakes as total failures. We tell ourselves that we are too weak, that we just can’t do it, so why try?

This self-talk also impacts our immune system – negative thinking suppresses our immune system, leaving us more open to catching whatever “bug” is going around. Haven’t you noticed that positive people rarely get sick? Our emotions impact our stress, our gut, and our immune system. That’s why so much of the above list actually relates to our emotions around the Holiday season.

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