There have been many songs that relate the emotional condition of love to a physical condition or even illness. But this may be the first to liken love to an allergic reaction.
Actually, love itself is not the allergen-- the woman in question is: "...my heart is allergic/ To the women I love." This is not just a case of society or family keeping lovers apart. It's our speaker's own body physically rejecting what his heart emotionally wants. (It has happened that someone has an allergic reaction to another person; often its that person's perfume or pet that's the culprit. But rarely, even one's body chemistry can trigger an allergic response in another.)
What about his brain? It's on the side of his heart: "My head intercedes with my bodily needs/ And my body won’t give it a break." And that makes it worse, because if he could logically determine that this is a problem, he might be able to address it. Instead, his mind is part of the problem.
Also, it's not just one woman. It's all the "women" he loves. So this isn't about one woman being wrong for him. It's all women, so the problem must lie with him.
On a biographical note, this is Simon's "breakup album" upon the end of his brief marriage to Carrie Fisher. The fact that it is his second divorce might lead to the pluralization of the word to "women."
Now, an allergic reaction is an auto-immune response and is not the same thing as a parasite or infection. Nevertheless, it at least feels to him like "Something’s living on my skin."
He tries medical interventions: "Doctor, please/ Open up, it’s me again." He even seeks the care of out-of-town specialists: "I go to a famous physician/ I sleep in the local hotel." (Maybe he needs a psychologist instead?)
But nothing helps: "the people like me/ We get better/ But we never get well." As it happens, this simple thought is one the stronger lines in a relatively weak song.
Even as a novelty song, it is somewhat thin-- Simon has been much funnier ("Pleasure Machine" springs to mind). This next one-liner falls particularly flat: "Where do allergies go/ When it’s after a show/ And they want to get something to eat?" (The drum even responds with a "ba-dum-bum" sting, as if it were a joke.)
The concept that is less explored, brought up by the pun "Maladies/Melodies," might have been worth exploring on its own-- the idea that the compulsion to make music is a form of sickness.
And the idea of being physically unable to be with someone you emotionally desire a worthwhile topic to deal with in a song. But that song is not this song. Here, the topic is raised and discussed, but never really explored.
We meet someone with a medical condition, we learn of his symptoms and treatment, but we don't get to know its mental impact. It would be like a song about a cancer patient that merely recites the chemotherapy schedule. Actually, such a song, which would reflect the patient's feeling of being reduced to a series of dates and dosages, might prove a more effective piece.
Even as a throwaway, this song does not rise to the wise flippancy of "Have a Good Time," the goofy fun of "We Got a Groovey Thing Going," or the wry shrug of "Papa Hobo."
But seriously, folks-- "Allergies to dust and grain" was not a lyric that needed to be sung.
Next song: Hearts and Bones