People are allergic to all kinds of things. In this Moment of Science, we discuss an allergy that might be kind of, well, disgusting.
If you're allergic to dust, chances are what's making you sick is dust mite fecal matter. Each tiny dust mite defecates about twenty times a day. The tiny pellets are your very own dead skin. They eat the dead skin that flakes off of our bodies each day--50 million or so flakes per body per day. They really like the mold growing on those flakes of dead skin.
Like I said, what makes you sick might be the fecal matter from the dust mites. The tiny pellets are about the size of a grain of pollen. They float through the air for a while before settling, and when allergy sufferers inhale them, their immune systems overreact, causing their mucous membranes to release a number of substances, including histamine. Histamine is what causes allergy symptoms like sneezing, runny nose, coughing, and swollen eyes.