If antihistamines don’t help, you may be dealing with a sinus infection. Most often, sinus infections are viral and will clear up on their own without medical care. However, if symptoms don’t improve after a week, it’s a good idea to seek medical care. That could be a sign of a bacterial infection that will require antibiotics to treat, she says. Antibiotics won’t help treat a viral sinus infection, which is far more common than the bacterial variety.