although i know we are all different and might have our own perspective on one-itis, from my experience it has less to do with physical attraction, but with the ability to see into things and constructing fantasies that are not very much related to what is really going on. if it was only about being horny ..., well i never experienced one-itis when watching porn, although i have several favourites here

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i myself had two different experiences with one-itis, one where i got so well along with a girl that i thought that must be love, i truly could connect to her, she would even end my sentences with the words i would have used. AFC back then i had no clue what to do, keeping it very "friendly" and it all ended in a mess, confessing love and shit. the other example was way different, i walked thru the local grocery store at my university and turning my head i saw this girl right in front of me, which blew my mind. it really stroke me and there was nothing i could do about it. and no she was not a perfect 10 but a very nice 7-8. not sure if i was triggered like a pawlow dog because of all i had conditoned myself so far, but i simply "knew" that this is HER. good thing was i managed to talk to her, i knew she was interested because she talked to her friends about me, but i blew it completely when we had our casual conversations. there was always this awkward silence and it broke my heart, i thought it should all go without saying but it certainly didn't there was no real flow, no connection, i had no idea how to open to her back then and it became real bad in the end. but still everytime i ran into her the years after my heart would make a little jump and go very sad, but hell i am over it now

another bad thing: a very, very cute girl (petite with incredibly beautiful eyes) got totally into me in a similar way (she just saw me, and got stroke herself i guess) but i "decided" to keep it "real" and not to go after her. from another experience i also learned that some girls can deliberately do things that make you not only like them but that can make you almost addicted to them, trained like a little puppy.
one-itis therefore i would say may have different faces, but it is all in your head, it is not "real", usually you project a lot of things and get blinded for all what may shatter this dream. besides the very normal habit that we attribute to beautiful people all the good things, whether this is based on reality or not, we are also prone to project our ideal "Anima" into some and these encounters usually dont work out because she would feel that it is not completely about her. what the woman wants is to be truly seen and accepted for what she really is, you want to touch the soft spots, explore the dark spots, assure her weak spots.
The more and more you become yourself, do not seek your missing things in others but are ready to accept what is offered to you, the less one-itis becomes an issue. there is a good side-effect from PUA i think, that is not only you have to be really interested for comfort but you bring the good things that you enjoy about her also down to earth with c+f and negs. the whole interaction becomes more human and real and thus you enhance your chances to find "the one" one day if this is still your interest.