Links Between Dehydration And Asthma

Dehydration is not typically listed as an asthma trigger. But, based on my own experience, I am convinced there is a link between dehydration and asthma. Research linking the two is sparse, to say the least. Still, I did find some evidence to piece the two together. Here is what I learned.

What happens when you’re dehydrated?

So, most of us with allergies know about histamine.^1-4 We know of it as a mediator of inflammation. It’s stored in mast cells lining most tissues inside our bodies. It’s used by the immune system to cause inflammation. This inflammation helps trap and kill pathogens. It’s also involved in both the allergy and asthma responses.¹

Histamines

But, histamine also plays another very important role. It’s also a neurotransmitter. It regulates the flow of water throughout your body. It makes sure all your cells stay well hydrated. So, when your cells recognize water levels are low, they begin releasing histamine. At least this is one theory.

Elevated histamine levels are recognized by the hypothalamus inside your brain. This we know for certain. This is proven by science. The hypothalamus signals the release of a hormone called vasopressin or anti-diuretic hormone (ADH). This hormone is received by your kidneys. It tells them to put water back into your bloodstream. It prevents you from peeing. This is a natural mechanism to get your body to conserve water.

Our theory postulates that histamine works to ration water throughout your body. It diverts water away from non-vital areas of your body, like your skin. It diverts water towards your vital organs, like your lungs. It makes sure your lungs stay well hydrated.

How does dehydration trigger asthma?

Histamine also has a local impact. Let’s take a look at its impact on your lungs. To make sure your lungs stay hydrated, it dilates blood vessels inside your lungs.^1,4-5 It also makes the walls of these blood vessels permeable. So, blood flow slows down and some of the fluid in these vessels seeps into spaces between cells. This causes airway inflammation.

This we know. This is proven by science. But, our theory adds to this. Our theory suggests that this process also works to keep cells hydrated. That’s why all this happens.

Airway inflammation alone makes airways narrower than normal. It also causes an increase in mucus production. It also causes smooth muscles wrapped around airways to spasm and constrict.  This is what causes your asthma symptoms: chest tightness, wheezes, increased sputum production, and shortness of breath.

Does dehydration trigger exercise-induced asthma (EIA)?

Now, this theory is a little better established than the one noted above.^6-8

Our noses are responsible for humidifying inhaled air to body temperature. With vigorous activity (i.e. running), you breathe so rapidly you’re nose can’t keep up. Plus, many of us breathe through our mouths while running. So, this causes airway cells to give up some of their moisture to humidify inspired air. The end result here is localized airway dehydration. This is a well-accepted theory explaining exercise-induced asthma (EIA).

Cold air, dehydration, and asthma

This is exacerbated when inhaled air is cold. This is because cold air tends to hold less water. So, this causes airway cells to work overtime to humidify inhaled air. Plus, cold air must be warmed, so airway cells have to also give up some of their heat. So, cold air may further dehydrate your airways. This may explain why cold air is also an asthma trigger.

This causes airway cells to release mediators of inflammation like histamine. This is a well accepted theory, and I explain it in my post “Exercise Induced Asthma.” Less well accepted is that histamine is released due to dehydration.

But, there are studies showing that dehydration can make EIA worse.  And there are studies showing that staying well hydrated may prevent EIA. ⁷ So, it’s certainly possible dehydration may have an impact on EIA.

The link between dehydration and asthma

Dehydration is not usually listed as an asthma trigger. So, it’s not something we typically expect to trigger asthma symptoms. It's an unusual symptom. But, it’s certainly something to be wary of in our efforts to obtain ideal asthma control. For  tips on how much water to drink, check out our post, “Hydration In Asthma.