Some types of mold can be a health risk for some people. Reaction to mold is highly variable and is dependent upon the type of mold, as well as how much of it exists in the home. It is clear that some people are allergic to mold. Further, some populations are more susceptible to negative effects from mold exposure. Those who have allergies, asthma, or pulmonary conditions may be more susceptible, as well as children and infants. Those with suppressed immune conditions, like HIV/AIDS may risk developing fungal infections in the lungs due to lengthy mold exposure.

The primary response to mold is an allergic response. Not all people are sensitive to mold in this way, just as not all people are allergic to pollen. In minor forms, mold exposure can cause hayfever symptoms like runny nose, itchy eyes, and sore throat.

Some people develop asthma as part of an allergy response to mold. This is one of the severe symptoms of mold allergy. Asthma can be dangerous and can become progressively worse if mold exposure continues. When possible, those who have an asthma response to mold should have their environments as mold-free as possible. However, this can be challenging.

One can generally clean the mold one can see, such as that which exists on walls. There is plenty of mold we don’t see, both indoors and out that may cause health issues. Air purifiers may help reduce airborne spores of mold that one can't see. Keeping mold from regrowing by wiping down windows if they become moist, and keeping bathrooms clean may also help reduce mold in the home environment. Bathrooms should never be carpeted, as carpet can harbor mold and be difficult to clean.

Allergy response to mold can also lead to greater risk for sinus infections. In fact those who appear to have chronic sinus infections without a viral cause may in fact be expressing allergies to mold. Again, trying to rid the home of any visible mold is helpful.

The greatest danger of mold is the possibility of developing fungal infections in the lungs. This generally only occurs in those with weakened immune systems. Fungal infections can be challenging to treat, and are worsened when one already has a suppressed immune system. Anti-fungal medications can treat fungal infections, but many of them have adverse side effects.

One type of mold, Stachybotrys chartarum, is sometimes called toxic mold. It tends to develop after a home has been flooded. People do show a higher allergic response to it, and it should be eliminated with bleach cleaning when possible. It is also a good idea to replace carpets that have been exposed to flood waters.

Some studies have suggested a possible link between hemorrhage in the lungs in infants and exposure to Stachybotrys chartarum. The Centers for Disease Control (CDC) reports that there is currently scant evidence to support a connection between pulmonary hemorrhage and this type of mold, or any type of mold exposure. However, possible risk, even if remote, suggests removing such mold from one’s home as quickly as possible, particularly if one has a young child or if one suffers from allergy to mold.