Toxic mold symptoms may occur if a person or persons have been exposed to high levels of spores in the atmosphere. These spores are the fruiting bodies of fungus. For them to germinate and survive, conditions need only be right and these will start to grow into fungi. These bodies can produce what is known as a mycotoxin, it does not appear to be used by them, but is like a by product of their existence and is the chemical which can cause the poisoning from yeasts, mushrooms and molds, and it is this which destroys the host.

Toxic Mold Symptoms Photo by Skelekitten via Flickr
Mycotoxins may be only a problem if fungi grow in large colonies, and continually produce spores which can produce further colonies. Nearly all fungi use oxygen and are found just about everywhere, but because they are so small it can be hard to see some of them with the naked eye. They live where the temperature and the humidity are right, and feed on organic matter. Different mycotoxins can be produced by a single species and it may also produce the same as other species.
They can grow in a house on the dust which collects behind things or under/in bedding, on the floor and in many other places. Dish cloths, tea towels, stale fruit and other food in refrigerators, damp washing which is not done for several days, or damp rooms will all produce these types of things.
The spores are quite normal in these conditions. The problems arise when conditions are bad enough that they proliferate, and in this case, there may be an allergic reaction to the level of spores in the atmosphere. The symptoms of a high level may be an attack of asthma, sinus problems, infections in the throat and the nose, conditions where the eyes are sore or inflamed, irritation of the respiratory tract and other allergic reactions.
This is especially a problem in a person who is undergoing treatment, or has a disease which lowers the immune system. In this case they are usually inhaled and start to grow on the living tissue in this area, attaching to the cells of the lungs. It is then that the mycotoxins can do their damage.
Houses are not the only places where conditions can be right for this type of problem. The work place is another, especially if it is damp and has a considerable amount of closed atmosphere where the spores cannot diffuse. In an open aired work area there is far less chance of this sort of thing being a problem.
For those who would like to keep mold to a minimum, then perhaps changing dish cloths and towels each day, not allowing damp dirty washing to remain unwashed, keeping the level of dust in the house down by vacuuming fairly often and changing bed linen often as well, may be some places to start.
It would appear that minimising those things that become stale and are apt to collect dust, plus removing stale food from the refrigerator may be a good place to start.