Is milk good when you have the sniffles?

No: It has been assumed in the past that consumption of milk increases production of mucus in the throat and upper respiratory tree. This appears to be untrue according to recent studies, but milk does contain a protein that becomes "sticky" in the mouth and throat. I would guess that this would worsen the sensation of pressure at the back of the throat, making sniffles worse. But this is just theory.

Milk & congestion.: It's traditionally thought that milk increases congestion, but I'm not aware that this has ever been proven as actual fact. That being said, warm fluids like tea and soup would be better.