Here a couple of poses for your yoga tool kit whenever you are plagued by hay fever or sinusitis.
The first one comes via the California-based yoga teacher Donald Moyer and is a version of savasana. In the photo, you see Heather lying on a long double-folded blanket, with a triple-fold blanket under her shoulders. A tightly rolled yoga mat is covered with a soft cloth and supports the occiput (base of the skull).
The second pose pictured shows me in sarvangasana supported on a bolster placed about 25 cm. from the wall. Variations of niralamba sarvangasana will serve to help drain the sinus passages.