Cockroach allergy

What it is

Cockroach allergy is a reaction to proteins in cockroach saliva, droppings and shed body parts.¹ About 30 cockroach species are linked to human homes, and two dominate indoors: the German cockroach (Blattella germanica) and the American cockroach (Periplaneta americana).⁴ Two important cockroach allergens are named Bla g 1 and Bla g 2. Bla g 1 is made in the cockroach’s gut and passed in its droppings, which are also called frass.⁴

Tiny particles from cockroaches are a common part of household dust and may be the real cause of what seems to be a dust allergy.³ Even dead cockroaches can cause allergic reactions.²

Symptoms it causes

Cockroach allergen causes symptoms when particles are stirred into the air and breathed in.² Symptoms can include sneezing, a runny or stuffy nose, postnasal drip, cough, and itchy, red or watery eyes, and some people get itchy skin or a rash.² Cockroach allergy is a common trigger of year-round allergy and asthma.² The symptoms can become chronic, lasting beyond the usual allergy seasons.¹

When cockroach allergy triggers asthma, symptoms can include wheezing, chest tightness, shortness of breath and waking at night.² Sensitization is common among children with asthma who live in inner cities. An estimated 30 to 40% are sensitized, and in some cities 70 to 80%, compared with 21% in one suburban group.⁴ In the National Cooperative Inner-City Asthma Study, children who were both allergic to cockroaches and exposed to high levels at home had more hospital stays and medical visits for asthma than other children.⁵

Where it’s found

Cockroaches live in all kinds of buildings and neighborhoods.¹ They are common in crowded cities and the southern US, and their allergens likely play a large part in asthma in many urban areas.⁷ They need both warmth and moisture, so they are found mostly in southern latitudes and rarely in the north unless buildings are heated. Infestation is less likely in single-family homes in colder climates and more likely in multi-unit buildings.⁴ Their presence does not mean a home is dirty.⁶

Indoors, German cockroaches favor food preparation areas and garbage, while American cockroaches prefer dark, damp places such as sewers and basements.⁴ Allergen collects in kitchens and in carpets, upholstered furniture and mattresses.⁴ In the inner-city asthma study, cockroach allergen was found in 85% of children’s bedrooms.⁵

US agencies and allergy societies describe these ways to cut exposure:

• Store food in airtight containers, and clean up dishes, crumbs and spills right away.⁷
• Put away pet food dishes after meals, and use kitchen garbage bins with lids.⁶
• Fix and seal leaky faucets and pipes, and block places where cockroaches can get in, such as crevices, wall cracks and windows.⁶
• Use integrated pest management, which combines several control steps. It appears to work best, and pesticides should be used carefully, ideally by a professional.⁴
• Clean or remove places where allergen builds up, such as contaminated carpet.⁴

Gains can fade. In the inner-city asthma study, cockroach allergen was lower 6 months after the work but back to its starting level at 12 months, and an AAAAI work group says continued effort may be needed.⁵