you need an exam by an eye doctor. yes, it is possible that this is allergy (although allergy usually occurs in BOTH eyes at the same time...). there are way, way too many things that could cause uniocular red eye for me to be able to tell you what you have here in this forum.
since its in one eye only, and seems to be lingering, one of the many possibilities is episcleritis, which would not be helped by naphazoline. go get seen by someone.
naphazoline and tetrahydrozoline have their place in medicine. here's my opinion on when they should be used:
1) "oh no! my wedding is this afternoon and my eye is red! what will i do about the photos?"
2) "i have a job interview and my eyes look terrible. i dont want them to think i'm a druggie"
3) "i was up all nite with my sick kid and my eyes are red, but now i have an important board meeting"
etc etc. i tell people to only use naphazoine for TEMPORARY redness reduction when you have to be SEEN by someone and look normal. thats it. it does not ever fix any eye problem. it just masks the redness, and only temporarily at that.
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