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Why are my TBI symptoms worse in the heat?

Related links:

Ottawa Public Health: Extreme Heat & Humidity

Centres for Disease Control & Prevention: Warning Signs and Symptoms of Heat-Related Illness

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If you’re in the northern hemisphere, then it’s mid-summer. And depending on where you are, it could be ridiculously hot outside.

Do your symptoms get worse with heat and humidity? I know mine do. I experience more fatigue, more headaches, more blah-ness all around. I was never completely sure why — is it because the summer has more daylight hours to trigger light sensitivity? Is it because I’ve upped my activity?

Both of these are probably true, but I’ve also come to realize that the hot humid weather plays a part in my increased summer symptoms. And hey, I found some research to prove it 🙂

So for you, here are 5 facts about the heat and the brain that can help explain your symptoms.

1) The brain is just vulnerable to the heat

In hot and humid weather, a person without a brain injury can feel fatigued, light-headed, nauseous, dizzy… does any of this sound familiar? Heat truly does affect the brain because the brain is not protected from heat like other parts of your body.

Clipart image in all black of hands around a brain

One of the ways your body cools down is to dissipate the heat through sweat. But the brain can’t do that. The brain depends on blood flow coming from the rest of your body to cool down. This is slow. As a result, the brain stays warmer for a longer period of time, and this makes it vulnerable to higher temperatures.

2) A brain injury may make it harder for your body to control it’s temperature

Your body keeps itself around a temperature of 37 degrees Celsius. This is pretty tightly controlled because even just a few degrees deviation can make a difference in how your body works.

Thermometer, Summer, Heat, Sun, Temperature

But what do you think helps control the temperature in your body? Answer: your brain. The pituitary gland in the brain helps with many things in the body, including body temperature regulation. We are finding more and more people with TBI have issues with the pituitary, and so it’s possible that a TBI can hinder the body’s ability to cool down.

3) Some medications and supplements used in TBI might affect your body temperature

Some medications and supplements can affect how the body regulates its temperature. For example, amytriptaline is on my personal list of meds, and the bottle often comes with a sticker that says to limit UV exposure. This is because amytriptaline and certain other anti-depressants can make a person more susceptible to UV rays and consequently, the heat.

There’s also a documented case of heat illness that came from using some Chinese herbal supplements. This is just a reminder that because a product is natural, doesn’t mean it has no side effects.

Medicines and supplements strewn across a table

Meds and supplements can be an important part of your treatment. They all have side effects and it’s important to know how to manage these should you experience them.

4) Signs & symptoms of heat illness are a lot like TBI — one aggravates the other

The body can acclimatize to hot and humid weather to a certain degree. But during a heat wave or those first couple weeks of high seasonal averages, your body can have a hard time handling it.

Heat illness is when your body temperature rises to a dangerous level, and the body can no longer keep itself cool through sweating.

Heat illness can be mild in the form of dehydration. It can progress to heat exhaustion, which has more severe symptoms like blurred vision, headache, upset stomach. Any person with even just a couple degree raise in body temperature can have cognitive dysfunction, like short-term memory problems.

Man holding his head outside

So if you already have a TBI and you are struck with dehydration or heat exhaustion, the symptoms can pile up real fast.

5) Severe heat illness can cause cognitive problems, neurologic problems, and even brain damage

Heat illness isn’t to be taken lightly. Dehydration can cause fatigue, light-headedness and confusion, and as mentioned above, heat exhaustion becomes more serious with more cognitive and digestive problems.

The most severe form of heat illness is heat stroke. Heat stroke can cause disorientation, seizures and loss of consciousness. Heat stroke can also cause serious brain damage and is overall life-threatening. Heat stroke is an emergency requiring medical attention.

Good news…heat illness is preventable!

It seems clear that the heat affects the brain. Preventing heat illness can prevent worsening of some of the shared symptoms you already experience with TBI. But for everyone, preventing serious heat illness will prevent brain damage too!

Hammock, Relax, Tree, Shade, Sleep, Nap

So prevent heat illness:

Limit your sun and heat exposure when you can. Wear a hat, sun block, loose fitted clothing and stick to the shade!

Avoid strenuous activity at peak UV hours. Where I am that is from 11am to 4pm.

Be aware of the signs and symptoms of heat illness. Call 911 (or your emergency number) right away if you or someone you know might have heat stroke. Follow your city’s public health guidelines, which generally include moving to a cool/dry place, laying down and resting, applying cold water to the skin then fanning the skin, along with applying ice packs to various areas of the body. For full details check out Ottawa Public Health here or the Centre for Disease Control and Prevention here.

Stay well hydrated with water or a sports drink. If you’re sweating more than usual, the salt will be helpful! Avoid or limit alcohol and caffeine as these can dehydrate you more.

Photo Of Woman Leaning On Handrail having something to drink

Stay cool everyone — both physically and metaphorically 🙂

Krystal Merrells

Registered Dietitian

Concussion survivor

Melting in +44 degree celsius heat


Alosco, M. L., Knecht, K., Glickman, E., Gunstad, J., Bergeron, M., & Hart, J. (2012). History of Concussion and Exertional Heat Illness Symptoms among College Athletes, International Journal of Athletic Therapy and Training, 17(5), 22-27. Retrieved Jul 8, 2020, from

Atkins, C. M., Bramlett, H. M., & Dietrich, W. D. (2017). Is temperature an important variable in recovery after mild traumatic brain injury?. F1000Research, 6, 2031.

Deng, H., Wu, X., Wu, L., & Zhang, H. (2014). Unusual heat stroke caused by herbal therapy with traditional Chinese medicine. Neurosciences (Riyadh, Saudi Arabia), 19(2), 130–133.

Dubourg, J., & Messerer, M. (2011). Sports-related chronic repetitive head trauma as a cause of pituitary dysfunction, Neurosurgical Focus FOC, 31(5), E2. Retrieved Jul 10, 2020, from

Griesbach, G. S., Tio, D. L., Nair, S., & Hovda, D. A. (2013). Temperature and heart rate responses to exercise following mild traumatic brain injury. Journal of neurotrauma, 30(4), 281–291.

Walter, E. J., & Carraretto, M. (2016). The neurological and cognitive consequences of hyperthermia. Critical care (London, England), 20(1), 199.


  1. Gunta Edwardson

    This is very relevant and informative. I was outside for most of the day near water, but did not feel well afterwards. Now I understand why. Keep well and stay cool.

    • Krystal Merrells

      I’m so glad this was helpful for you! Yes, you keep well and stay cool too 🙂


    Super helpful, thank you! Do these symptoms get better after a few weeks of the summer heat? Im wondering if I need to move somewhere cooler because of these crazy heat symptoms.

    • Krystal Merrells

      Hi Sara! Thank you for taking in the post and leaving a question 🙂 I believe it’s possible for the symptoms to improve as generally people can acclimatize to whatever environment they are in. Personally what I find difficult is fluctuating temperatures/ humidity/ pressure. And I’ve also heard some people with dysautonomia that came along with their injury may have temperature intolerance. But decisions around moving should consider a lot of things! Social & community support are super important for recovery, in my opinion. Moving can come with all sorts of other challenges. An OT and/or therapist can also help with those decisions. Hope this helps!

    • christina Clarke

      Tbi and menopausal symptoms what is best climate for winter I love on east coast should I live in Arizona fir sinter months or is cold weather better

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