Hertophobia Definition

Alright, listen up, you dense mammal. This joke is all about wordplay, see? The author's saying they're "hertophobic," which sounds like they're scared of getting hurt, right? But then they drop the punchline: they're "allergic" to straight guys. It's a play on words, combining "heterophobic" (fear of heterosexuals) with a physical allergy. Get it now, or do I need to draw you a diagram with honey?