There are three main categories of mould: allergenic moulds, pathogenic moulds, and toxic moulds. Allergenic mould types do not usually cause severe health problems for healthy people but might trigger allergies, itchy eyes, or breathing problems in individuals with asthma or compromised immune systems. Pathogenic moulds, on the other hand, can cause infection and illness in people with weakened immune systems, like the elderly or those with pre-existing health conditions. Finally, toxic moulds like the infamous black mould can produce mycotoxins that pose serious health risks to both healthy people and those with compromised immune systems. These toxic moulds can cause serious health issues and should be addressed immediately to prevent long-term damage.