MIAMI BEACH, March 6 - There has been a significant rise in allergic sensitization to ladybugs, an aphid-eating friend to farmers, in many parts of the U.S. because the insects may swarm indoors to get out of the cold, researchers reported here.
In presentations at the American Academy of Allergy, Asthma, and Immunology meeting, several groups of investigators said that ladybugs -- or more precisely, Asian lady beetles (Harmonia axyridis) -- are an attractive nuisance that can cause allergic reactions in areas where they swarm in high concentrations.
Action Points
- Consider hypersensitivity to ladybug/beetle antigens in patients with seasonal allergies who have exacerbation of symptoms during periods of high infestations.
- This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.
"In some houses there are thousands and thousands of ladybugs," said Kusum Sharma, M.D., of the University of Louisville School of Medicine. "You go into the basement and the whole floor is covered with piles and piles of ladybugs."
She and colleagues conducted an anonymous survey to determine whether exposure to Asian lady beetles in high numbers could result in significant allergic sensitization.
They found that of 99 respondents, 50 reported being sensitive to the bugs, 19% reported allergy symptoms when they came into direct contact with the insects, and 31% said they used more allergy medications during seasonal ladybug infestations, which occur primarily when the bugs come indoors in the fall, and make themselves at home until spring.
"One of our conclusions is that health professionals should be aware that this is a problem, and if patients have fall-winter allergies, they should ask the patients whether they have ladybug infestations, because patients will not come out and tell you," Dr. Sharma said in an interview.
In fact, allergy to ladybugs-beetles may be nearly as common as sensitization to cats or cockroaches, according to David W. Goetz, M.D., an allergist in Morgantown, W.Va.
In a review of about 1,400 skin prick tests performed in his practice, 21% of tests showed sensitivity to ladybug allergens, compared with 24% sensitivity to cats, 27% to cockroaches, and 40% to dust mites.
Among patients with single-allergen sensitization, 10% were allergic only to dust mites, 6% to 8% reacted to only cockroaches or ladybugs, and 4% were allergic only to cats.
Although there was close correspondence between sensitization to cockroaches and ladybugs, sensitization to ladybugs was greater among patients living in rural areas compared with urban areas.
"Ladybug is a very important allergen, so if in areas where there are infestations you're not testing patients for ladybug sensitivity, 8% of the time those negative skin tests may actually be ladybug positive," Dr. Goetz said in an interview.
The correlation between ladybug and cockroach sensitivity seen by Dr. Goetz was also detected in a study of 12 patients conducted at the University of Virginia in Charlottesville by Takuya Nakazawa, M.D., and colleagues.
They identified 12 patients with symptoms that included cough, rhinitis, conjunctivitis, and acute asthma. The patients were exposed to beetle antigen and were shown to be hypersensitive to it. But the researchers also found that ladybug antigens would produce a high number of false-positive tests for cockroach, indicating a high degree of cross-reactivity.
Dr. Sharma said that the best way to cope with a ladybug infestation is to simply vacuum them up -- HEPA filters not needed -- and to seal off potential entry points by caulking windows and doors.
Dr. Goetz warned, however, that sucking up the insects may permanently clog a standard household vacuum cleaner. Whether an industrial shop vacuum might be better is possible, but untested, he added.
Primary Source
American Academy of Allergy, Asthma and Immunology annual meeting
Source Reference: Sharma K et al. Ladybug Hypersensitivity Among Residents of Homes Infested with Ladybugs in Kentucky. Abstract 118, presented March 4.