There are a number of health concerns related to exposure to mold. These include respiratory problems, an increase or development of asthma, allergy symptoms such as rashes, runny noise, scratchy throat, itchy or red eyes, coughing, wheezing and fatigue. In extreme cases exposure to mold can be toxic and lead to severe infections.
Sometimes it is easy to identify the source of mold - either visually or by a musty odor. However, often it can hide behind cabinets, paneling and walls, in duct work, under carpets, or anywhere that moisture gathers - a critical environmental factor that leads the growth of mold and mildew. So it's imperative that you not only remove the mold you see, but that you trace it to it's source and mitigate the cause of the moisture that led to it's growth in the first place.