Why Though? with Dr. Matt Agnew

Why Does Looking at the Sun Make Some People Sneeze?

Why Though? with Dr. Matt Agnew

Show Notes

Have you ever walked outside on a bright sunny day and suddenly sneezed... with no dust, no pepper, no cat fluff anywhere? Just sunshine and a sneeze? There's a real science reason behind it.

Dr Matt Agnew investigates the sun sneeze mystery. What even is a sneeze? Why does bright light trigger one for some people? And why does it run in families?

What you'll learn: Sneezing is your body's nose cleaning button... a blast of air that clears anything annoying from your mucous membrane When bright sunlight hits your eyes, your brain urgently signals blink and squint For about 1 in 4 people, the blink button and the sneeze button sit really close together in the brain... so pressing one accidentally bumps the other Scientists call this ACHOO Syndrome... short for Autosomal Dominant Compelling Helio-Ophthalmic Outburst Sun sneezing is linked to your genes, which means it can run in families Sun sneezes won't hurt you... but stop before the sneeze hits if you're on a bike or crossing the road

Key Science Ideas: Mucous membrane: The sticky lining inside your nose that catches dust, germs and anything annoying Optic nerve: The nerve that carries signals from your eyes to your brain ACHOO Syndrome: The scientific name for sun sneezing... and yes, the acronym was absolutely intentional Genes: The instructions inside your body that decide things like eye colour, height, and apparently whether sunshine makes you sneeze Reflex: An automatic body response your brain triggers without you choosing it

Fun Experiment: The Family Sun Sneeze Survey Ask everyone in your family whether they sneeze when they look at bright light. Try a torch in a dark room if the sun isn't cooperating. Keep track of who does and who doesn't. If sun sneezing runs in your family, you'll start to see a pattern... and you'll have just conducted your first genetics experiment at the kitchen table.

Why Though? The show for little scientists who love asking big questions. Follow or subscribe so you never miss an episode.

Follow Dr Matt Agnew: Instagram: instagram.com/drmattagnew TikTok: tiktok.com/@drmattagnew YouTube: youtube.com/@whythoughpod Website: drmattagnew.com

Find Why Though? podcast across the internet and share with your friends! Instagram: instagram.com/whythoughpod TikTok: tiktok.com/@whythoughpod Facebook: facebook.com/whythoughpod

Hosted on Acast. See acast.com/privacy for more information.

More from Why Though? with Dr. Matt Agnew

Jul 11, 2026

The ground beneath your feet feels completely still... but the continents are actually moving all the time. In this episode of Why Though?, Dr Matt Agnew explains why continents drift across the Earth, how tectonic plates slowly carry them around the planet, and how that movement creates mountains, deep ocean trenches and earthquakes.

Jul 4, 2026

It looks like magic. It makes spooky fog that pours down instead of floating up. And it never leaves a puddle. So what is dry ice actually doing?

Jun 27, 2026

A cheetah? A race car? A rocket? All great guesses. All completely wrong. The fastest thing on Earth is something you can't hold in your hand... and understanding it means understanding lightyears, the speed of light, and why space distances break normal numbers.

Jun 13, 2026

Here's something nobody tells you. Most of a fart has absolutely no smell. So what's actually making everyone pinch their nose?

Jun 6, 2026

Lightning and thunder happen at exactly the same time. So why does the flash always arrive before the boom?

See all episodes →