Meths for Mosquito Bites?

Why does yawning produce tears? Why do noses tend to run on a cold day? Is methylated spirit good for mosquito bites? Why do computer screens sometimes produce after-images on your eyes? Can blocking blood vessel growth cause cancers to stall? Is cola good for bloat? Is it really colder just as the sun rises? More top science questions from South Africa, as well as news of how the cornea keeps itself clear of blood vessels...