If your redness
is recurrent in the same eye,it has to be examined under the slit lamp in an eye clinic. Some times sinus congestion will simultaneously affect the eyes producing conjunctival congestion alone which recovers once your sinusitis
is relieved. Although sinusitis will cause headache, any refractive error
should also be ruled out.
Cold compresses for 5-10 mins ,few times a day ,with an antihistamine vasoconstrictor eye drop
four times a day ,will help you symptomatically until your ophthalmic visit.