Why is it hazardous?

The prevalence of mould in the environment means people are continually exposed to small amounts of it without apparent harm. However, harm may occur if a person is exposed to high levels, if a person has a pre-existing susceptibility to a species of mould (e.g. an allergy), or if a person has a weak or compromised immune system (e.g. when recovering from a major operation).

Some moulds produce irritant and toxic substances (mycotoxins) that can cause symptoms of ill-health or allergic reactions. Symptoms include skin rash, dermatitis, asthma, sneezing, headache, and in extreme cases neurological problems and death.