Bed bugs can give you nasty bites and a lifetime of nightmares, but scientists have long wondered if the creepy parasites can pass diseases to their hosts. For years, the general consensus was no: Unlike ticks, mosquitos, and other insects that are known to feast on human blood, bed bugs aren't packing any harmful pathogens in their bites. Yet according to a new study, spotted by Gizmodo, the bugs don't need to nibble on us to make us sick. Histamines in their poop might be aggravating our immune systems.

For their study, recently published in the journal PLOS One, scientists at North Carolina State University tested the dust in a bed bug-infested apartment complex. They found that samples from some infested homes had histamine levels 20 times higher than those without bed bugs. This was still the case three months after the buildings had been treated by exterminators.

Histamine is a chemical compound produced by our bodies. In small amounts, it works as a vital part of our immune system. It's activated in the presence of allergens, irritants, and pathogens. Say a puff of dust goes up your nose: Histamine is what prompts your body to sneeze it out. It's also the culprit behind the watery eyes, runny nose, and itchy skin you might experience during an allergy attack (which is why you might take an antihistamine to calm these symptoms).

But we're not alone in our ability to produce histamine. Recent research has shown that the chemical is present in bed bug feces. When the insects poop, they spray histamines into the same air that homeowners breathe. A few whiffs of the stuff is likely nothing to worry about, but scientists are concerned about the effects environmental histamine can have on people over an extended period of time. The chemical compound can cause allergic reactions on its own and possibly make us more vulnerable to existing allergens. The implications are especially serious for people with asthma.

"Dermal, nasal, or respiratory responses (e.g. bronchial reactivity) to histamine in clinical tests suggest that exposure to histamine in the environment would constitute a significant health risk, although information on environmental exposure is limited," the study authors write.

For now, scientists can do nothing but speculate on what these results might mean for public health. Humans are prepared to treat only histamine that's produced by our own bodies, and dealing with the effects on histamine spread by bed bugs is uncharted territory for doctors and scientists. How exactly bed bugs obtain the chemicals in the first place is also unclear, but researchers suspect that it's a combination of the blood they suck from us and histamine they make on their own as a type of pheromone, indicating to other bed bugs that a place is safe to invade.

Following this study, the North Carolina State scientists plan to conduct more intensive research on the impact histamine produced by bed bugs is having on the people who live with it. While the best way to eradicate histamine in bed bug poop is still a mystery, there are plenty of ways to deal with the bugs themselves if you suspect you have an infestation.

[h/t Gizmodo]