Bed bugs are more dangerous to human health than previously thought. Besides their nasty bites, the feces of these tiny parasites could trigger a severe allergic reaction even after they are exterminated.

This lasting effect is due to raised levels of an organic compound present in the insect's poop known as histamine. Those who regularly pop allergy pills are certainly familiar with the name.

The chemical is not all that bad. In fact, it is naturally produced by the human body as a response to harmful pathogens or to repair damaged cells.

Histamine exposure, however, is an entirely different story. Upon skin contact or inhalation, it can cause a variety of health problems ranging from rashes to respiratory disorders.

Such findings were uncovered by a group of researchers at North Carolina State University as they investigated pest-free and infested homes.

In a paper published Feb. 12 in Plos One, they report that histamine levels are significantly higher in infested homes and persistent in pest-free ones, with elevated levels lasting for months.

Tracking Histamine Levels In Raleigh Apartments

The groundbreaking study was conducted in an apartment complex in Raleigh with a chronic bed bug infestation.

Dust samples were collected from specific units prior heat treatment of the facility. Three months after the blood-sucking insects were eliminated by increasing indoor temperature to 50 degrees Celsius, researchers obtained another set of samples.

Histamine levels in the two sample groups were then compared with a third's coming from nearby homes which have been declared pest-free for a minimum of three years.

Based on lab results, the researchers concluded that heat treatment may eliminate bed bugs but not the histamine they produce. Apparently, the chemical has the ability to withstand raised temperatures as evidenced by increased levels even when the apartments were already pest-free for months.

According to one of the researchers Zachary DeVries, heat treatment should be coupled with meticulous cleaning to minimize the amount of dust, which carries bed bug feces.

"We'll also further investigate the effects of histamine in an indoor environment, including chronic exposure to histamine at low levels," he says in a report.

Using A Chemical Compound As Natural Markers

The bed bugs excrete poop that is naturally rich in histamine content to mark locations they deem as suitable for aggregation. This explains why bed bugs tend to gather in a specific spot when they invade a home. Among their favorite choices is the bedroom, where they can easily feed on the blood of sleeping humans.

A previous research published in the Wiley Online Library two years ago also found histamine in cuticles shed by the insects after enjoying a blood meal.