Bed Bug Infestations Can Raise Histamine Levels in Infested Homes

Histamines produced by bed bugs can persist for some time after bed bugs have been eliminated. (Photo: Matt Bertone)

A new study from North Carolina State University shows that histamine levels are substantially higher in homes infested by bed bugs than in uninfested homes. The study also found that these histamine levels persist for months – even if the bed bugs have been eliminated from the home. These findings suggest that bed bugs may be more than just a mere nuisance pest. The bed bug-produced histamines could pose a serious health risk in the indoor environment.

NC State post-doctoral researcher Zachary DeVries and colleagues from NC State and the N.C. Dept. of Health and Human Services conducted a Raleigh-based study to compare histamine levels in homes with and without bed bug infestation. The researchers also evaluated the persistence of histamine following bed bug eradication.

“Histamine levels in bed bug infested homes were at least 20 times higher than histamine levels in homes without bed bugs,” DeVries said. “And these levels didn’t decrease much three months after treating the infested homes with heat and insecticides.”

Histamine was recently identified as a close-range aggregation pheromone component in bed bug feces. Exposure to histamines in the environment can provoke allergic responses and asthma. High concentrations of histamine can readily become airborne and represent the major route of entry of allergens into the airway, as documented in studies correlating cockroach allergens in settled and airborne dust. The potential health risks associated with bed bug-produced histamine might rival those associated with other indoor pests, namely cockroaches and dust mites.

Using a Raleigh apartment complex as a study site, the researchers collected the household dust in apartments with bed bugs and those without. Those apartments with bed bug infestations had substantially higher histamine levels in dust than apartments with no evidence of bed bugs as well as “control” apartments some miles away that had no history of bed bug infestation.

The researchers also tracked histamine levels over time after having infested apartments professional heat treated. Histamine levels did not decline significantly three months after treatment, showing the chemical’s capacity to persist despite extreme heat.

“A combination of heat treatment to eradicate bed bugs and rigorous cleaning to eliminate some of the household dust could be a way to reduce these histamine levels; we’ll do future testing to bear that out,” DeVries said. “We’ll also further investigate the effects of histamine in an indoor environment, including chronic exposure to histamine at low levels.”

The research appears in PLOS ONE. Coby Schal, Blanton J. Whitmire Professor of Entomology at NC State, co-authored the paper along with research specialist Richard Santangelo. Alexis Barbarin of the N.C. Dept. of Health and Human Services also co-authored the paper.

Funding for the work came from the U.S. Department of Housing and Urban Development, the Alfred P. Sloan Foundation, the National Institute of Environmental Health Sciences, and NC State’s Blanton J. Whitmire endowment.

Rodent-Proofing for Winter

Winter months are rodents’ most active time for entering structures as they search for food and shelter from cold temperatures. Now is the time to begin taking steps to rodent-proof structures, both inside and out.

Keep them out! Remember, mice can squeeze through an opening the size of a dime or larger, while rats can get through openings quarter-sized or larger. Locate and seal up any gaps on the building exterior. Depending on the size of the opening, screen, sheet metal, steel wool, or copper scrub pads may be used to seal openings. Caulk may be used in some cases, but may not be as long lasting. Make sure all doors and windows tight fitting with weather stripping. Exterior doors should have door sweeps installed.

Figure 1. Debris and other clutter around buildings can harborage rodents (Image: Mike Waldvogel, NCSU).

Don’t give them a place to hide! Reduce or eliminate unnecessary clutter, both indoors and outside. Keep potential shelters such as piles of wood, bricks or stones away from the foundation of your house to discourage rodents from setting up camp right outside (See Figure 1). Rooms or closets with lots of clutter can also provide hiding places for rodents. A little organization goes a long way in eliminating those potential homes for rats and mice.

Figure 2. Mouse damage to a bag of grass seed (Image: Mike Waldvogel, NCSU).

Don’t feed them! Store susceptible food items in sealed, pest proof containers. This includes the foods we eat – like cereal, grains, and rice – as well as pet food, birdseed, and even grass seed (see Figure 2).

Do some landscaping! Rodents can gain access to buildings by climbing across tree limbs and entering the attic or eaves. Trim back trees and shrubs so they are not in direct contact with the foundation so that you can easily spot and address new points of entry that develop.

Taking the steps outlined above can help you make it through the winter months without unwanted guests!



Eastern Equine Encephalitis


Adult asian tiger mosquito resting on foliage

Asian tiger mosquito (photo – Susan Ellis (

Late Friday  (10/13), the Jacksonville Daily News reported that a pony had died of what is suspected to be Eastern Equine Encephalitis (EEE) which is transmitted by mosquitoes.  In 2016, there was one reported veterinary case of EEE and that was in Pitt County.  In 2015, there were five veterinary cases including one in Onslow County.  Human cases of EEE are uncommon.  According to the CDC  n the ten year period (2007-2016), North Carolina had eight human cases of the disease.

It’s important to understand that the virus is not transmitted from one horse to another (or from a horse to a human) or from one person to another.  Also, mosquitoes acquire the virus from feeding on infected birds primarily down in the hardwood swamp areas in the southeastern part of our state (where fewer people live).  This unfortunate incident doesn’t mean that people need to run out and treat their property with pesticides. It does serve as a reminder that, even though temperatures are starting to drop, it’s still a good idea to use personal protection when engaging in work or recreational activities outdoors.  Also, while we’re outdoors cleaning up fallen leaves and pine needles and/or planting flowers or shrubs for next spring, it’s a good idea to look around at areas that are or could be mosquito breeding grounds and eliminate them.  More information about mosquito control can be found here: