Margen
Spiciness isn't a taste, it's a trick. The molecule behind it, capsaicin, latches onto a receptor on your tongue called TRPV1, the very same one triggered by real heat, above around 43 degrees. Your brain gets the same signal as if you were being burned, even though the chilli is cold. That's why you sweat, tear up and reach for water.
And that's why water doesn't help: capsaicin is oily and won't dissolve in it. Milk, on the other hand, has casein, which drags it away. So a dairy product cools the fire far better than a glass of water.
The strangest part is who it doesn't affect: birds. Their version of the receptor doesn't react to capsaicin, so they peck at chillies unfazed and scatter the seeds as they fly. The burn, deep down, is the plant choosing its postman.