Do you know what happens to your body when you eat chillies?

Burning mouth? Inflamed hands? Runny nose? Sweats? Heartburn?

If you like your food hot then you're probably only too familiar with these feelings. The effects that come with eating spicy food are caused by capsaicin - a small chemical that can be found in chilli peppers.

What happens to our body temperature when we eat hot chillies? We decided to find out using our FLIR One thermal imaging camera, which converts invisible infrared radiation into an image. Here is a timelapse of what happened to our guinea pig. Over the space of eating a total of five scotch bonnets (which The Pepper Scale say is one of the hottest chilli peppers in the world!) our guinea pig’s temperature changes a total of 2.6 degrees, going from 27.1 to 29.7 degrees in just a few minutes.

We then did the same experiment on another guinea pig. Normally our vision is limited to a small portion of the electromagnetic spectrum, but through thermal imaging that portion of the spectrum we perceive is dramatically expanded, helping us “see” heat. Thermal imaging cameras measure relative heat, showing hot spots and cold spots.

As you can see from our before and after images, the camera indicates the changes in the hot and cold spots, with blue representing cold temperature, yellow representing warmer temperature, red being hotter and white being the hottest.

Before After

But why does your body react the way it does?

And why do so many of us savour the pain- inducing burn at all? We put together this infographic to help explain what’s going on in our guinea pig’s body above:
Spiciness isn’t a flavour, not like sweet or sour - it’s just the result of the activation of pain receptors in the body. The chemical that causes the spiciness in chilli peppers is capsaicin, which is what creates the burning sensation when eaten.

Your body actually views capsaicin as an offensive substance which needs to be immediately flushed out. Capsaicin latches on to pain receptors in the nose, mouth, and skin, which are normally only activated in the presence of heat. It irritates the mucous membranes in the nose, causing them to be inflamed.

Nutritionist Melissa Calendar explains “capsaicin irritates your mucus membranes, especially the ones in your nose, so as a defence mechanism they produce more mucus, causing your nose to run so the extra amounts of mucous are actually a defense mechanism to try and keep out the unwanted substance.”

The sensation produced by the capsaicin is the same sensation that heat would cause, which explains the burn. The capsaicin tricks the nerves and sends messages to your brain. This signal turns the nerve cell on to allow it to trigger other nerve cells that will carry the message to the brain that it has to respond to this dangerous temperature - hence the sweating that often accompanies a spicy meal - this is the body's reaction to try and cool itself down.

So why the red face and hands? The redness on your hands and face is another sign of your body attempting to cool off. Capillaries below the skin dilate in response to the “heat,” and blood rushes through them to move heat to the surface of your body, where it can more easily radiate away.

Going back to our guinea pig, we can see the effect of this:

Before After

Notice how in these before and after shots, his hands have gone yellow which shows that the body is attempting to cool itself down. In reality, our guinea pig’s hands were very sweaty!

As the capsaicin makes its way down your throat, you might also experience heartburn. But don’t reach for the Gaviscon straight away! Usually, it’s not a genuine episode of heartburn, which is typically caused by acid reflux, but the capsaicin binding to the TRPV1 receptors in the esophagus, which prompts a burning sensation similar to heartburn.

Do you also suffer from painful cramps after a chilli eating session? This is another defense mechanism to clear out the “heat-causing” contents in the intestine by moving them as quickly as possible towards the colon. Glands along the gut wall also may secrete more fluids, which can sometimes lead to the most unpleasant outcome of chili consumption: diarrhea. Not nice.

So why do so many of us like to eat something which tricks our brain into thinking our tongue is on fire?! Scientists believe it’s because it activates areas of the brain related to both pleasure and pain. The relief felt after the initial sensation of spice-induced pain actually leads to pleasure.

Vegan food expert Pamela Elizabeth, the restaurateur behind Blossom and Blossom Du Jour restaurants says one of the most interesting things about spicy food is that "it can heat up your body when it's cold out and, surprisingly, can cool your body off when you are hot. Eating spicy food makes you sweat and sweating actually helps your body temperature regulate itself. So while it may seem strange, definitely put more heat on your food when the heat is on."