[[caption-width-right:250:What IS love? The President wants to know, and Honomi is ''more'' than willing to find out for her.]]

One thousand years ago, a child was born from an unusual cherry tree in the mountain town of Tokitami. While having the form of a human, the girl lacked one important thing: a heart. Without a heart, she could never understand love, and as a result her short life eventually came to a tragic end.

In the modern age, in the same town, another child is about to be born from the same unusual cherry tree. However, the spirit of the cherry tree wants to avoid the same mistake that happened before. Before the child is born, she wants to have it learn love... But what does she know about love? She's a tree spirit! However...

She could have someone ''else'' teach her what love is.

For this task she "volunteers" an unlikely pair for the task: Yamano Tasuku, a boy who ''hates'' love, and Morioka Honomi, a girl who is literally allergic to love. Will these two be able to teach the tree spirit love, and avert the tragedy from happening again?

Another story from Satoru Akahori, the creative mind behind ''Manga/KashimashiGirlMeetsGirl'', ''Manga/SorcererHunters'', and ''Anime/SaberMarionetteJ'' (among other series), and drawn by Yukimaru Katsura (who also drew the ''Kashimashi'' manga), Love Allergen is a romantic comedy that follows the two kids as they figure out the answer to that all-important question: what truly ''is'' love?

The series is considered complete, with 30 chapters published.

* AbandonedArea: Takimi Land, an abandoned theme park where Honomi and Tasuku (with Aki in tow) have their first "date".
* AddedAlliterativeAppeal: Tasuku's childhood friend's name is Miya Miyako ([[Manga/BambooBlade Miya]]-[[VisualNovel/EfAFairyTaleOfTheTwo Miya?]])
* AllergicToLove: Honomi, in a literal case. In fact, one of the conditions she has for participating in the cherry tree spirit's mad scheme is that she be cured of her allergy.
* AloofDarkHairedGirl: How other people see Honomi (she's very aloof and proper). Subverted, as it's all just an act started by her mother so that people, boys in particular, would be too intimidated to approach her. Honomi herself has gotten ''very'' good at the role, but one of the first things she admits to Tasuku is how tiring it is to keep up.
* AnimalMotifs: Honomi and Tasuku's relationship is symbolized in-setting by the dogs Kuu-chan and Non-chan, with the bigger dog often dragging off the much-smaller dog to God-knows where. Even Miyako was given a dog counterpart, a small maltese sporting the same ribbon as hers.
* AsleepForDays: Happened once while Honomi was young, during a bout of love allergy. The experience was described as particularly harrowing for her family.
* BarbieDollAnatomy: The President is like this.
* BigFancyHouse: Or rather, big fancy ''inn''. The Morioka Inn (owned by, lived in, and managed by Honomi and her family) is even considered a town landmark and point of pride.
* BishieSparkle: Rampant.
* {{Bishonen}}: Tasuku is like this, and he absolutely ''hates'' it. He would rather be a rugged manly-man like his father.
* BridalCarry: Guess who this happens to a lot? Here's a clue: it's not the girls.
* BrotherSisterIncest: Both of Tasuku's older siblings have shades of liking him a little ''too'' much.
* ChickMagnet: If Tasuku leaves his face uncovered, he draws in every female within a hundred feet of him. In his mind, this is ''not a good thing.''
* ChildhoodFriends: Aki and Honomi, Miyako and Tasuku.
* ChildhoodFriendRomance: What Miyako wants to upgrade her relationship with Tasuku to. The major problem with this is that Tasuku pretty much still treats her like a male friend.
* {{Cloudcuckoolander}}: Honomi has a ''lot'' of strange ideas about how a person goes about showing love, and falling in love, that's for sure.
* CoolBigBro: Along with CoolBigSis, this is what Tasuku's two older siblings ''think'' they are. They're not.
* DeadpanSnarker: After being exposed nonstop to Honomi's enthusiasm, it's not surprising that Tasuku turned into this.
* DeclarationOfProtection: The other third of Aki's motivation to watch over Honomi.
* DitzyGenius: Honomi. Everyone who isn't in the Love Experiment Association however (the teachers in particular) only see her behaved and straight-A's honor student side.
* DraggedByTheCollar: Tends to happen a lot, usually at the hands of Honomi.
* DraggedIntoDrag: Not surprisingly Tasuku is often a victim of this too.
* EveryoneCallsHimBarkeep: The cherry tree spirit is never named, and is only referred to as "President".
* ExhaustedEyeBags: Honomi gets a bad case of these after several straight days of writing exchange diaries for Tasuku to read.
* FauxToGuide: A hilarious example in Honomi's treasured "The Steps To Love" book. The guide's first step is the partners learning to stare dreamily into each other's eyes. The last step? [[spoiler:''Eloping'' with your loved one.]]
* GenkiGirl: Honomi's ''real'' personality is highly energetic.
* GoldDigger: What Aki initially takes Tasuku for. She's quickly corrected of this mistake.
* GratuitousEnglish: Yoshiha is fond of spouting this. Usually accompanies her delusions of her little brother.
* HairDecorations: The President's two large flowers, and Miyako's large hair ribbon.
* HeroicSecondWind: A minor version, where Hiromi recovers from her mental and emotional fatigue when she misinterprets Tasuku's disinterested signature at the end of her exchange diary as a challenge (it isn't).
* IJustWantToBeNormal: Tasuku would rather ''not'' be the center of attention (and attraction) of people.
* IJustWantToBeSpecial: Kind of strange, when the one who wants excitement is the ''spirit of a cherry tree'', but there you go. She even says so herself [[http://www.mangareader.net/love-allergen/1/34]]!
* InformedAttractiveness: Honomi is supposedly incredibly beautiful and elegant (as observed by Miyako), but going just with the manga art alone it's hard to say that she's prettier than the rest of the female cast, or ''Tasuku'' for that matter.
* InformedAttribute: Tasuku's older brother Kanji is supposedly a brilliant medical student, with at ''least'' two internationally-published papers to his name, but you wouldn't know it from just looking at him, because most of a time he acts like a big brocon.
* InnocentlyInsensitive: Tasuku can sometimes be like this.
* InSeriesNickname: "Master" for Tasuku, Myaa-Myaa for Miyako.
* ItsAllMyFault: Aki secretly blames herself for Honomi's first occurence of "love allergy".
* JumpedAtTheCall: Honomi was very enthusiastic when she heard the cherry spirit's proposal.
* LikeBrotherAndSister: Tasuku insists that this is his relationship with Miyako. Technically true, but Miyako is secretly having other ideas...
* LoveTriangle: Another of the "steps" found in Honomi's manual. Surprisingly, Honomi herself doesn't take the role of Tasuku's girlfriend for the roleplay -- that's Aki's job. Instead she plays TheRival.
* MagicAntidote: The prize for helping the cherry spirit/President is a cure to the allergies that plague both Tasuku and Honomi. Tasuku's allergies are cured immediately (just to convince him that it's really true), while the rest of the series can be seen as the work needed so that Honomi can get hers.
* {{Megane}}: Tasuku has a pair with thick lenses, though he also spends an equal time with them off.
* {{Meganekko}}: Tasuku's elder sister Yoshiha.
* MissingMom: Virtually nothing is known about Tasuku's mother, and just by the story itself, one would think that he and his older siblings were raised by his father alone.
* MustMakeAmends: Related to ItsAllMyFault. Aki joins the Love Experiment Association (and by extension the President's scheme) to make up for technically causing the first onset of Honomi's "love allergy".
* TheNicknamer: Honomi obviously.
* {{Ninja}}: Honomi is, for all intents and purposes, a kunoichi, with the expected reflexes, speed, and jumping abilities, but none of the usual ninja gear or focus on stealth.
* {{Nosebleed}}: A common occurence where Tasuku's older siblings are concerned.
* NotWhatItLooksLike: Aki ''obviously'' misinterprets what Honomi and Tasuku were doing when she walks into them at the end of chapter 2.
* TheOjou: Honomi is treated like a noble lady by many people and it is justified later on. It is revealed that not only is she the daughter of the owners of the town's premiere inn, her family apparently owns a good chunk of the land the town is built on, not to mention the forests and mountains surrounding the town.
* OnlyThePureOfHeart: Only people who are pure-hearted can be invited, or indeed enter, the root chamber under the blue-flowered cherry tree that the President resides in.
* {{Otaku}}: Tasuku is, much to Aki and Honomi's surprise, a ''massive'' abandoned building maniac. He promptly geeks out once the trio arrives at the location of their "first date", the abandoned Takimi Land.
* RapunzelHair: The President again.
* ReallySevenHundredYearsOld: The President. Justified, in that she's technically an ancient sakura tree that's been standing for more than a thousand years already.
* ReincarnationRomance: The backstory to the "love triangle" roleplay that Honomi cooked up. Not surprisingly, Tasuku is supposed to be the reincarnation of the ''girl'' of the reincarnated pair.
* TheRival: Honomi's role in the "love triangle" roleplay. She soon decides that she doesn't like it, because it makes it seem like she's missing out on the fun Tasuku and Aki are having.
* SoBeautifulItsACurse: Tasuku, again. As noted by his brother, he's been the victim of ''at least'' 28 kidnappings, 880 instances of attempted molestation, [[EvenTheGuysWantHim from either gender]], and is constantly in danger of being hit on if he didn't have his face obscured. No wonder the kid hates his own face.
* StartMyOwn: The Love Experiment Association. Formed for the express purpose of "researching" what love is.
* TheStoic: Tasuku's father is a man of few words to say the least, and doesn't really show his emotions much during his interactions with his family. Rather than alienate him from Tasuku, the latter thinks that it's kind of cool, and something he should emulate to become a "man among men".
* SuperReflexes: Honomi has these. Aki as well, but to a much lesser degree. To quote Tasuku, "These guys have reflexes equal to a mountain animal."
* ThirdPersonPerson: Honomi.
* TrademarkFavoriteFood: The President's manjuus. Makes one wonder how she gets them, given how she's pretty much stuck under the Cherry tree...
* UmbrellaOfTogetherness: Sharing an umbrella is one of the things that Honomi enthusiastically wanted to try.
* WiseTree: The blue-petalled cherry tree is an aversion, in that the tree spirit inhabiting it is clueless about the modern world, or people in general.
* YaoiFangirl: Yoshiha.