Sinus headaches are the result of swelling, inflammation or infection in one or some of the sinuses in your head. Many sinus headaches exhibit the same symptoms as tension headaches or migraines, but often have additional symptoms such as congestion, cough, sore throat, fatigue, or nasal discharge. They can be triggered by allergies, pressure changes in the ear, tooth infection, a cold, a bacterial sinus infection, or sinusitis.  While it is important to consult your doctor to accurately diagnose the type of headache you are experiencing, there are a number of different ways you can treat a sinus headache using both medical and home remedies. In general, most sinus headaches and swelling are gone within four to eight weeks with or without medical treatment. 
Antihistamines work by blocking histamine, a substance produced by your cells to prevent infection.  If your body detects a foreign substance, your cells will make histamine, which causes inflammation of blood vessels. Usually this is useful. But when your body mistakes a non-harmful substance, like pollen, for a harmful one, it can cause what we call seasonal allergies.  Antihistamines are commonly known for treating seasonal allergies, but there are several other uses for both over-the-counter antihistamines and those prescribed by a doctor. Before taking antihistamines, understand how antihistamines work and what symptoms they treat.