Risks and Prevention of Asian Ladybug Allergy

Asian ladybugs (Harmonia axyridis) were artificially introduced in the United States in the early 20th century as a means of pest control. While the colorful insects were highly effective at culling aphid populations, they were ill-suited to survive colder temperatures and quickly began to move indoors.

By the mid-1980s, the Asian ladybug population had grown to such a size that many rural and suburban communities had begun to experience severe and potentially hazardous home infestations.

Today, these infestations have been reported all along the East Coast as far south as Georgia and in states like Wisconsin, Kentucky, Missouri, and West Virginia. With these have come reports that people have begun to develop allergies in direct response to these non-indigenous creatures.

Causes

While health officials were initially skeptical about claims that the otherwise harmless ladybug could cause symptoms of allergic rhinitis, conjunctivitis, asthma, and hives, evidence in 1998 established a clear link.

According to the research, the Asian ladybug produces a chemical called isopropyl methoxy pyrazine (IPMP) which it uses to deter predators. The chemical is present in the insect's "blood" (known as hemolymph) which it reflexively releases whenever agitated. The substance not only has a foul odor (similar to that of wet hay), it leaves a visible, orangish stain on surfaces and fabrics.

What the scientists were able to confirm was that that ladybug hemolymph could trigger an allergic reaction in some. This was evidenced by blood tests which showed the presence of allergic antibodies specific to IPMP in the affected individuals.

In addition to "reflex bleeds," ladybugs can also bite humans, presumably to get salt from the skin. While the bites are barely felt, they can sometimes cause localized irritation and an allergic cutaneous (skin) reaction.

Frequency

In certain parts of the country, such as West Virginia, positive allergy tests to Asian ladybugs are as high as 21 percent. The rate of positive results is nearly as high as those for cockroaches (27 percent) and a little more than half that of dust mites (40 percent).

The allergies are considered seasonal as they most often occur in autumn and winter months. Depending on the region, the season can last anywhere from September to March.

Prevention and Treatment

The best way to prevent a ladybug infestation is to seal all cracks and openings that they can crawl through. This includes adding flexible door and window sills to completely seal off the home.

If there are bugs inside the house, use a vacuum cleaner rather than a broom to gather them. Sweeping may trigger a reflex bleed. In addition, place a nylon stocking over the vacuum cleaner hose to bag them rather than letting them collect inside the machine. In this way, you can dispose of them quickly with minimal exposure. Wash your hands with warm soap and water after doing so.

If allergies do occur, they should be treated in the same way as an allergy to dust mites, pollen, or pet dander. This may include the use of antihistamines and other allergy medications. While there is no treatment for ladybug allergies per se, allergy shots have been explored in persons with a positive allergy test result.