What can happen to you if you inhale a small quantity of mold or mildew?

Most likely nothing: Mold spores are naturally occurring in our environment, both indoors and outdoors. We likely inhale mold spores frequently with no problems. Inhaling mold spores would only become a problem if there is a high amount, and you had a chronic condition like asthma or severe allergies to molds, then inhaling spores could cause an increase in asthma symptoms like difficulty breathing, cough, wheeze, etc