Bedbug waste contains high levels of the allergy - triggering chemical histamine, which stays behind even after the insects are eradicated. (sciencenews.org)
Experiments have shown that the itch - inducing chemical histamine, released in irritated skin by certain white blood cells, causes an itch only after a delay of one to two seconds. (newscientist.com)
In addition, when the researchers tried to trigger attacks with dust mites and the inflammatory chemical histamine (thought to be released in response to the mites), rabbits treated with antisense DNA were insensitive. (sciencemag.org)