You can buy one at a drugstore, or make your own. Sniff this solution out of the palm of your hand, or put it into a clean dropper bottle. But once swelling begins, antihistamines may make it worse because they may make mucus thicker. If you have a cold or flu, or already have sinus pressure, don't take antihistamines. These medicines relieve the pain of sinus headaches.
Generic medicines are cheaper and just as effective as brand names.
Read the labels. Choose medications with only those ingredients you need.