Hay fever, a.k.a. seasonal allergies, is mostly caused by pollen. The condition usually starts giving you grief in the late summer and early fall. But experts say that recent warmer winters mean that pollen season is lasting weeks longer than before.
In some areas, that fine yellow dust given off by mountain cedar can trigger symptoms from mid-December into February. Mold spores, which can grow in freezing temperatures, can also cause winter allergies.