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The effects of salt water on dogs: the dreaded beach diarrhoea

Updated: Sep 10

I can't even begin to tell you how much my dog, Boston, loves the beach. She goes mental in the car at just the first whiffs of the salty sea air. She spends the whole time running around, jumping in and out of the sea, chasing her ball. She absolutely LOVES it. But we have to be careful that she doesn’t drink too much sea water accidentally while she’s chasing the ball…because we have seen with our own eyes the explosion that can occur out of her backend shortly after. It’s the dreaded beach diarrhoea that can take some of the fun out of the day. But why do dogs get this?’s all about those electrolytes.

People are most familiar with the term electrolytes when thinking about sports drinks. Electrolytes are minerals that carry an electrical charge when dissolved in water. Some examples of key electrolytes in the body are sodium, chloride, potassium, magnesium, calcium, phosphate, and bicarbonate. Many of them are essential nutrients, meaning that we have to get them through what we eat and drink. Electrolytes are required for basic bodily functions such as maintaining water and electrical balance and conducting electrical signals through muscle and nerve cells. We cannot function without them.

We also need them to be in a good balance too - as too much or too little electrolytes can cause issues. If we sudden intake a lot of electrolytes, say by drinking a lot of sea water, not all of the sodium and other electrolytes are able to be absorbed. That causes an osmotic draw and pulls fluids into the intestines, causing the subsequent explosive diarrhoea. That is what happened to Boston after she drank too much seawater.

On the other hand, we want to make sure electrolytes are replenished if they’re lost. Typically, we lose electrolytes through vomiting, diarrhea or sweating. In dogs though, they sweat very little in comparison to humans, so they don’t lose electrolytes through this method as much as we do. But they have been documented to lose some during hard exercise, or at least they have lower levels in their blood. The body of evidence suggests that 1 gram per 1,000 kcals of diet is the adequate intake for sodium, chloride and potassium in dogs that are doing a fair bit of exercise (1). Don’t fret too much though for your weekend warrior, as most canine diets are already well above this; so don’t feel the need to reach for an electrolyte supplement for them! What would we recommend then? Just some normal, good ol’ fresh and clean tap water.


1. National Research Council. 2006. Nutrient Requirements of Dogs and Cats. Washington, DC: The National Academies Press.

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