Date Published: February 12, 2018
Publisher: Public Library of Science
Author(s): Zachary C. DeVries, Richard G. Santangelo, Alexis M. Barbarin, Coby Schal, Joshua B. Benoit.
Histamine is used in bronchial and dermal provocation, but it is rarely considered an environmental risk factor in allergic disease. Because bed bugs defecate large amounts of histamine as a component of their aggregation pheromone, we sought to determine if histamine accumulates in household dust in bed bug infested homes, and the effects of bed bug eradication with spatial heat on histamine levels in dust. We collected dust in homes and analyzed for histamine before, and up to three months after bed bug eradication. Histamine levels in bed bug infested homes were remarkably high (mean = 54.6±18.9 μg/100 mg of sieved household dust) and significantly higher than in control homes not infested with bed bugs (mean < 2.5±1.9 μg/100 mg of sieved household dust). Heat treatments that eradicated the bed bug infestations failed to reduce histamine levels, even three months after treatment. We report a clear association between histamine levels in household dust and bed bug infestations. The high concentrations, persistence, and proximity to humans during sleep suggest that bed bug-produced histamine may represent an emergent contaminant and pose a serious health risk in the indoor environment.
Indoor environmental contaminants pose serious health risks to humans. Well-investigated examples include human-generated contaminants, such as lead , asbestos  and various pesticides [3, 4], along with aeroallergens produced by pests such as house dust mites , cockroaches , and rodents . These pests share several common features: (a) they are often obligatorily associated with humans and present in large numbers; (b) some of the allergens they produce are excreted in feces and urine and persist in household dust; (c) environmental conditions (sanitation, temperature, humidity) can influence both pest populations and the persistence of allergens; and (d) allergen-containing household dust can become airborne and inhaled when disturbed [8–11]. Bed bugs (Cimex lectularius, Fig 1) share these features, but they are not known to produce allergens beyond those delivered with their bites.
Histamine was detected only at trace levels in homes known to be free of bed bugs, indicating that environmental histamine is of no concern in residences that are truly un-infested. On the other hand, we found a clear association between high levels of histamine in house dust and the presence of bed bugs, indicating that bed bugs are the major contributor to indoor histamine residues. Low, but detectable, levels of histamine in some un-infested apartments within the same building suggest either that bed bugs had been present in these apartments at some prior time, or that some bed bugs were present but we failed to detect them.
Bed bugs have become a major social, economic, and health problem since their global resurgence in the early 2000s. Infestations can reach exceedingly high levels, especially among the elderly and in disadvantaged communities, where interventions may be unaffordable. While bed bug bites have been recognized as a dermatological concern that can be exacerbated and lead to secondary infections, bed bugs have not been implicated as disease vectors or allergen producers. The results of this study demonstrate that the presence of bed bugs strongly correlates with histamine levels in homes, and thus may adversely affect the health of residents through exposure to exogenous histamine. Furthermore, bed bug eradication with heat and insecticides does not appear to reduce histamine levels in homes, suggesting high thermal and chemical stability of histamine. Future investigations should first expand the sample size of the present work, to ensure that our findings are not confounded by any other undetected variables. In addition, future studies should evaluate temporal and spatial dynamics of histamine deposition in bed bug-infested homes, health impacts of dermal and respiratory exposure to environmental histamine, and the efficacy of various mitigation strategies to reduce histamine in homes. The intimate association of bed bugs with humans and the spatial distribution and persistence of histamine in homes suggest that histamine may represent an emergent indoor environmental contaminant whose impact on human health should be investigated.