Can They Cause Allergies?

This is one of the few home-invader health claims where the common fear turns out to be accurate, and this hub's job is to say so plainly rather than reflex-debunk it. Nakazawa and colleagues, writing in the Journal of Allergy and Clinical Immunology, purified two major beetle proteins — Har a 1, roughly 10 kilodaltons, and Har a 2, roughly 55 kilodaltons — and found they bound IgE antibody in 65 and 75 percent of sera, respectively, from patients living in beetle-infested houses. A clinical review by Goetz, in Allergy and Asthma Proceedings, describes ladybug-specific IgE hypersensitivity documented across all ages and both sexes, manifesting as rhinoconjunctivitis, asthma, urticaria, and angioedema, and notes that in some endemic areas ladybug allergy has been reported at a prevalence as high as 10 percent — with ladybug ranked alongside cat, cockroach, and house-dust mite among the allergens most likely to show up as an isolated positive skin test in an allergist's office. Exposure to accumulations of dead beetles indoors, not just live ones, can also provoke a reaction.

This is a genuinely different claim from the allergen finding, and it shouldn't be blurred into one vague 'they're unhealthy' statement. Extension entomology sources are consistent that these beetles do not carry or transmit infectious disease to people or pets; the health concern here is an allergic and irritant response to the beetle's own proteins and defensive fluid, not a pathogen the beetle is spreading. If you or someone in the household has persistent respiratory or skin symptoms that track with a beetle aggregation, that's worth raising with a physician or allergist — this page describes the documented biology, it doesn't diagnose an individual case. In New Hampshire, the exposure window is predictable: UNH Cooperative Extension reports these beetles are most numerous on the sunny side of buildings on mild days from mid-September through early November, which is exactly when a sensitized household is most likely to notice symptoms flaring, and sealing entry points before mid-September is the extension-recommended way to keep that fall influx out of the indoor air. For the related bite and reflex-bleeding facts this allergen finding connects to, see do-they-bite and the-smell-and-the-yellow-stain.