It was funny and the art was 'umehh'
I'm not sure if she was allergic it was something like that

What I remember:
School she applied to has girls and guys but she trys to avoid the guys, and one of them is trying to make her fall for him

Please Help

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~ stefan will make your day ~

Is it Koibana! Koiseyo Hanabi by Nanaji Nagamu?
The heroine (a girl named Hanabi) says she hates guys, but I'm not sure she said anything like she was allergic.

its probably not bitter virgin, but bitter virgin has almost the exact same setup, but its amazing

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"When god gives you lemons, find a new god."

or is it 'MARS'?

http://www.mangaupdates.com/series.html?id=1067

Kira believes that Rei and all other men in the world are dirty. She stays away from her classmates, hiding in her art. What happens when the delinquent motorcyclist and playboy, Rei, gets ahold of one of her drawings, and actually wants to keep it?

but Mars wasn't funny at all.

i second Koibana! Koiseyo Hanabi

what about Haruhana?
Yamada Hana's just moved to Tokyo, and her perfect debut falls disastrously flat. Not only do things at school start off badly, but her demon sister's sold her off to work for Haru, who seems to spend way too much time touching girls. If that wasn't enough, Haru's gorgeous, and Hana has a strange condition where she breaks out in hives whenever cute guys touch her!

it's not exactly what you're talking about, but it's similar with the allergy thing, and it's funny

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"Fashion is nothing but an induced epidemic." George Bernard Shaw

on second thought your description is not really clear so i am just gonna put more names that can fit in your description:

Maria Holic
Ichigo & Anzu
Kira Kira Labyrinth

even if they are not what you are looking for this time, you can still enjoy them since they have similar settings.

Well it doesn't fit too well, but it might be M to N no Shouzou
Come to think of it Tenjou no kajitsu might be closer to your description.
Note: I haven't read yet neither of this mangas, since I'm so picky I read a lot of descriptions so I just remembered this two. Oh well in case you decide to read them I hope you'll enjoy them.

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I love vampires.

Hmm... Kaichou wa maid-sama also fits this discription (almost). It's an ok shoujo. But I think you mean Koibana, too.

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"The light shines in the darkness, and the darkness has not overcome it."