Their natural habitat is in the nostrils of nuns over the age of seventy. They are accompanied by Allergephobia, which induces all sufferers to have a deep aversion to anything bearing a remote resemblance to pollen, dust, cats and husbands consuming more than one whiskey and soda.
It also causes one's breath to become extremely toxic, despite the insistence on handing out peppermints to anything with less than three legs.
A good way to rid one's presence of greenlump sufferers is to eat a jar of pickled onions prior to a possible meeting.
"Really? Perhaps she has greenlumps!"
"Nonsense, you've had quite enough!"