One particularly undesirable but common asthma trigger is cockroaches and may be found in the very cleanest of homes. About 20-60% of asthmatics are allergic to cockroaches. Exposure to cockroach antigen may cause coughing, nasal discharge, rashes, and wheezing in susceptible individuals. This could be one of the most important factors that have led to the marked increase in asthma, particularly in large cities. Children may be more likely to play indoors in crowded cities due to safety issues, which could explain why asthma prevalence has particularly increased in children.

Cockroach allergen is found in the proteins of their saliva, body and droppings. Cockroaches are found in all climates and environments, although they are most commonly found in warmer, more humid areas. They are prevalent particularly in crowded urban areas and older homes. It is estimated that 78-98% of homes have cockroaches. The average home may have between 800-300,000 cockroaches at any given time.

Skin allergy testing is necessary to confirm an allergy to cockroaches. Getting rid of cockroaches is not always easy and is best handled by professional pest exterminators. They generally are found in kitchens, bathrooms and basements where there is food and water as well as hiding places. It is essential to keep the trash covered and emptied frequently and avoid leaving food on counters. Food on counters and in cabinets should be stored in airtight containers. Wash and put away dishes as soon as possible. Repair any sources of moisture leaks, particularly under sinks and around pipes in basements. Use poison baits, boric acid and traps in prevalent areas in the home for continuing control, although avoid using these in homes with pets and young children. If sprays must be used, people with asthma should be kept out until the area is thoroughly aired out.

If antihistamines, anti-inflammatory and bronchodilators are not helpful in reducing allergy and asthma symptoms, allergy desensitization injections may be necessary.