Ladybugs = Human Allergens?

Although customers may see ladybugs as harmless pests, a new report says the beetles may cause asthma.

Just when you thought you heard the last about the pestiferous effects of ladybugs in buildings, a new report suggests they may also trigger allergies and asthma in people. The finding was made public in November by a Louisville, Ken., allergist, Dr. Hobert Pence, and was reported by Reuters, a national news service.

The clinical case study involved a southern Indiana man whose house was overrun with Asian lady beetles, Harmonia axyridis. The beetle has the habit of entering buildings in the fall in search of overwintering sites. Pence’s findings, presented at the American College of Allergy, Asthma & Immunology annual meeting in Chicago, indicated that the man "clearly had high levels of allergic antibody in his blood to ladybug proteins." Moreover, he had not suffered from asthma until his house was infested with thousands of ladybugs. His asthma was severe enough to be treated twice with daily medications.

While this may be one of the first apparent cases of ladybug-induced asthma, two cases of nasal allergies triggered by ladybugs were reported in Georgia earlier this year. Last winter, I received word from a pest control operator in Missouri that one of the company’s customers had also been diagnosed with ladybug-induced asthma by his allergist.

It’s hard to say how common such reactions will be in the future; Dr. Pence predicted they will be more common. I’m inclined to agree, especially if it turns out that symptoms can be brought on by previous accumulations of dead lady beetles in wall voids, light fixtures, ducts and other areas of the house. Such reactions are already well documented for house dust mites and cockroaches.

Lady beetles do not injure humans, nor can they breed or reproduce indoors like fleas or cockroaches. Nonetheless, some people will not tolerate insects of any kind in their home or office.

The easiest way to remove ladybugs that are indoors is with a vacuum cleaner. A broom can also be used to remove beetles indoors but is more likely to cause staining. (The orange-colored fluid that the beetles secrete when picked up or disturbed is harmless, but will stain walls and other surfaces.)

Because Harmonia axyridis seeks out overwintering sites in the fall, exterior cracks and crevices and openings can be sealed as a long-term, preventive treatment. Here are some additional preventive options:

• Adjust or install tight-fitting sweeps or thresholds at the bottom of all exterior doors.

• Seal utility openings where pipes and wires enter the foundation and siding. Holes can be plugged with caulk, cement, urethane foam, steel wool or copper mesh.

• Caulk around windows, doors, siding and fascia boards.

• Tell customers to repair damaged window screens and install insect screening behind attic vents.