Risks and Prevention of Asian Ladybug Allergy

Increased Rates Linked to Seasonal Infestations

Asian ladybugs (Harmonia axyridis) are generally harmless, but some people develop allergic reactions from being around them, touching them, or to their bites. The allergy symptoms reported from exposure to these bugs include allergic rhinitis, conjunctivitis, asthma, and hives.

Asian lady beetle
Wahyu Amrullah / Getty Images

Causes

Asian ladybugs were introduced in the United States in the early 20th century as a means of pest control. While the colorful insects are highly effective at culling aphid populations, they are ill-suited to survive cold temperatures, so they tend to move indoors when it's cold out.

By the mid-1990s, the Asian ladybug population in the US had grown to such a size that many rural and suburban communities began to experience severe home infestations. Infestations have been reported all along the East Coast as far south as Georgia and in states like Wisconsin, Kentucky, Missouri, and West Virginia.

Scientists have discovered that ladybug "blood" (known as hemolymph), which it instinctively releases whenever agitated, can trigger an allergic reaction in some people.

  • At least two allergens, Har a 1 and Har a 2, have been identified in these ladybugs.
  • A chemical called isopropyl methoxy pyrazine (IPMP) is used by the ladybug to deter predators. The substance has a foul odor (similar to that of wet hay), and it leaves a visible, orangish stain on surfaces and fabrics.

In addition to "reflex bleeds," ladybugs can also bite humans. While most people can barely feel the bites, 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%. The rate of positive results is nearly as high as those for cockroaches (27%) and a little more than half that of dust mites (40%)

The allergies are considered seasonal as they most often occur in the autumn and winter months. Depending on the region, this can last 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.

If you find Asian ladybugs inside your house, use a vacuum cleaner rather than a broom to gather them. Sweeping may trigger a reflex bleed.

Be sure to dispose of them quickly, rather than letting them collect inside your vacuum cleaner. And, if you have a strong allergic reaction, consider wearing gloves or a mask as you dispose of them to minimize your exposure. Wash your hands with warm soap and water after you finish handling the bugs and debris.

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 specific treatment for ladybug allergies, allergy shots have been explored in people who have a positive allergy test result.

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