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How Stress Can Shut Down Your Immune System

The lead-up to my thirtieth birthday was intense. My online business was still in a state of flux, which of course left me in a state of pure hustle. Building a community, securing new clients, all while trying to figure out the direction it would take—no one warned me it would be like this!

Fortunately, there was light at the end of the tunnel.

I was receiving positive feedback, successfully implementing new strategies and my fiancé decided to surprise me with a trip to the Bahamas! I was ready to burst with excitement! You’d better believe that I was going to bust my ass to make up for that vacation, though. From the moment I learned I was being swept away to paradise, I went into a mode that my fiancé lovingly calls “Business Katie.”





Seven months of it.

Anxiety built. Stress mounted. I didn’t care and it really didn’t matter because I was getting shit done. I was too busy knocking out some solid work in order to create a strong foundation to stand on once I returned from my trip. I wanted to succeed at all costs and no amount of birthday celebration was going to get in the way.

By the time we set foot in paradise, I was still wound so tightly that the first four days were less of a break and more of a transition. When Day Five rolled around, I gave myself permission to take it easy.

Day Six quickly became Day One of a six-week flu.

Suddenly wracked by my body’s desperate need to heal, I was lucky to fight it off long enough to get home. The timing wasn’t a coincidence. As is the case with many of the stress-related occurrences in my life, I was diving headlong into the effects that come after a modern-day fight-or-flight response.

So what happened?

Fight or Flight

Since the dawn of days, survival has been our number one focus. If we head back to the time of hunter/gatherers, encounters with lions, tigers and bears required an automatic response.


Run Away


Stay and Fight

Depending on how long you’re attacking or bolting through the woods, it’s unlikely that you’re going to remain in this state of fight or flight for more than thirty minutes tops. You’ve either killed, been killed or gotten away. Fortunately, you’re sitting here, reading this right now, because your ancestors made the right decisions in these encounters. This survival trait has been passed along through the generations and it’s deeply ingrained in our systems.

During this temporary state, your body is shoveling all of its mental powers into what’s important:

Pumping enough blood to your limbs

  • Increasing your heart rate

  • Increasing adrenaline to ensure that you have the energy necessary to sustain this state

As you can see, “immune system” isn’t on this list. Your body isn't worried about infection while it's fending off a wild beast or scaling a tree. It’s in a life-or-death situation. It’s got more important shit to do.

But what does that mean for you today?

Fast Forward to Modern-Day Stress

Stress doesn’t last for thirty minutes anymore. It’s not even an hour.

For many of you, the experience can last eight/ten/twelve/eighteen(!!) hours a day:

  • Hitting deadlines for Greg

  • Getting chewed out by Karen

  • All while sustaining, and hopefully building on, the life you want

These situations don’t put you into a heightened level of fight-or-flight, but it’s still enough to elicit a reaction. The kind of reaction that raises your heart rate or fires shots of adrenaline into your bloodstream. The kind of reaction that shuts down the activation of your immune system because who needs it, right? If we’re stressed, our body will continue to work in the same way it’s supposed to. It doesn’t consider whether or not we’re in a life-or-death situation, just that we’re stressed; it’s acting accordingly.

As a result, you won’t feel sick.

You read that correctly.

Your immune system works in a way where the best defense is a good offense. We’re coming into contact with things that could make us sick all the time, but our immune system is on it! Sometimes it’s fighting and we don’t even realize it. However, the symptoms you experience (fevers, for example) during a flu or cold won’t always appear during times of stress. Why should they? Your body is too busy to respond to the daily exposure of viruses and bacteria.

You’ve now made yourself vulnerable and you don’t even realize it.

Rewind to My Thirtieth Birthday

Once I allowed myself to relax, my body took a step away from the long-term effects of stress and started allocating resources and energy to the parts of my body that required maintenance. Having flung open the gates of hell for as long as I did, my body realized it had a lot of work to do.

Since it was no longer busy wrestling phantom bears or swimming away from imaginary sharks, it immediately raised my fever in order to burn off the uncomfortable amount of crap that had been successfully infecting my cells for the last few months. Getting the flu for six weeks was inevitable. It was so bad that it undid all of my hard work leading up to the holiday. I promised myself I’d never let it happen again and I’m happy to say that I’ve stuck to it!

In Conclusion

This could easily happen to you, if it hasn’t already.

Short bursts of the fight-or-flight response? Okay.

Long term? Not so much.

As it stands, there’s no one-size-fits-all solution to managing your stress, so it’s important to learn what your stressors are. Otherwise, you’re not giving your body a fighting chance.

Whether it be creating new habits or investing in a tennis ball, you need to manage your stress if you want to strengthen your immune system.

Be smart. Be safe.

Don’t be 30-year-old me.

First published April 2020

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