Mold (American English) or mould (British English), also sometimes referred to as mildew, is a fungal growth that develops on wet materials. Mold is a natural part of the environment and plays an important part in nature by breaking down dead organic matter such as fallen leaves and dead trees; indoors, mold growth should be avoided. Mold reproduces by means of tiny spores. The spores are like seeds, but invisible to the naked eye, that float through the air and deposit on surfaces. When the temperature, moisture, and available nutrient conditions are correct, the spores can form into new mold colonies where they are deposited. There are many types of mold, but all require moisture and a food source for growth. Health effects Mold is ubiquitous, and mold spores are a common component of household and workplace dust. In large amounts they can lead to mold health issues to humans, potentially causing allergic reactions and respiratory diseases. Mycotoxins Some mold produce mycotoxins, chemical components of their cell walls, that can pose serious health risks to humans and animals. "Toxic mold" refers to mold which produce mycotoxins, such as Stachybotrys chartarum. Exposure to high levels of mycotoxins can lead to neurological disorders and death. Prolonged exposure (for example, on a daily basis) can be particularly harmful. Mycotoxins can persist in the indoor environment even after death of the fungi. They can adhere to dust particles and can spread through the air attached to these dust particles or spores. There must be very specific temperature and humidity conditions in order for fungi to produce mycotoxins. Symptoms Symptoms of mold exposure may include nasal congestion; sinusitis; rhinorrhea, eye irritation; respiratory difficulties, such as wheezing, chest pain, cough, and persistent sneezing; throat irritation; skin irritation, such as a rash; and headache. Immunocompromised people and people with chronic lung illnesses, such as obstructive lung disease, may get serious infections in their lungs when they are exposed to mold. These people should stay away from areas that are likely to have mold, such as compost piles, cut grass, and wooded areas. Asthma Infants may develop respiratory symptoms as a result of exposure to Penicillium, a fungal genus. Signs of mold-related respiratory problems in an infant include a persistent cough or wheeze. Increased exposure increases the probability of developing respiratory symptoms during the first year of life. Studies have indicated a correlation between the probability of developing