Possible to get allergies for no apparent reason, i.e. same house, middle of winter, no changes in diet or places where i spend time/inhabit?

Possible: It is possible to get allergies in the winter since this is the time when house dust mites, one of the most potent and common allergens in temperature climate and low altitude areas, proliferate. If there has been water damage or pet exposure, your symptoms may exacerbate likely from spending more time indoors. However I didn't find any symptoms you listed to be suggestive of allergies.