What Are the Symptoms of a Mold Allergy?

The EPA says allergic reactions to mold are common and can be immediate or delayed, that repeated or single exposure to mold, mold spores or mold fragments may cause people who were not sensitive to become sensitive, and that allergic responses include hay fever-like symptoms such as headache, sneezing, runny nose, red eyes and skin rash. It says molds can cause asthma attacks in people with asthma who are allergic to mold. The CDC says that for some people, mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes or skin rash, and that people with asthma or who are allergic to mold may have severe reactions.

Some people face bigger risks. The CDC says people with weakened immune systems and people with chronic lung disease may get infections in their lungs from mold. The NIH National Heart, Lung, and Blood Institute says hypersensitivity pneumonitis happens in some people after they breathe in certain substances in the environment, such as mold, which trigger the immune system and cause short- or long-term inflammation. A 2021 systematic review in the Porto Biomedical Journal says several fungi that live indoors, most often Penicillium and Aspergillus species, have been associated with hypersensitivity pneumonitis after cumulative exposure.

The EPA advises keeping indoor humidity low, below 60 percent relative humidity if possible, and ideally between 30 and 50 percent.