Warrgh, that was unexpected. I picked up my toothpaste tube, squeezed it gently until toothpaste began to emerge from the nozzle … and there was a sudden pop, a fingertip-sized blob of toothpaste flew out of the tube and landed in the basin, and I was hit in the eye by a sharp puff of minty air.

There must have been a big bubble of air in the tube due to a manufacturing defect of some sort, and the instant there was no longer enough toothpaste blocking the nozzle to impede its bid for freedom, off it went.

But for all that the cause is comprehensible after the fact … I've never had a tube of toothpaste explode in my face before!