I started letting my dogs (labradors) sleep on my bed. Occasionally I would wake up to one of them heaving in the night but most of the time would get them on the floor before they threw up on the sheets and it was once in a blue moon. However, recently anytime my female lab has been on the bed she's thrown up without fail. It does not happen downstairs that I can see in their own beds, or in the garden, or when they are in their beds in the living room, but within half an hour of being on my bed now she barfs. Why is this? Is she making some sort of statement???? I love having them sleep on the bed with me, but I can't take this with her each time. They are happy dogs, lots of attention, walks, love... but why has this started happening out of the blue? She can go the whole night without doing it, unless she's on my good sheets!!!!