Mold proliferates where there is water damage, whether the source of the water is outside the building or coming from inside — such as a plumbing leak. Mold can grow in paper products, cardboard, ceiling tiles, glue, wood products, and insulation. It can also grow in water-damaged insulation, wallpaper, carpet, curtains and other fabrics, as well as any organic material. Mold can also be brought into the house on a person’s clothing or shoes.

And mold spores are very hardy — they can remain dormant for a long time waiting to grow. The time to grow comes when there is water exposure and the air is warm — such as in heated house.

Many of us have had the experience of smelling mold in a damp basement or other indoor space. It can even be seen as gray, black, or reddish areas around windowsills, pipes, or walls. People who are very sensitive to mold may respond to such exposure by experiencing a runny or stuffy nose, watery eyes, fatigue, brain fog, or difficulty breathing.

Over the past few decades, I’ve been seeing more and more patients affected by mold. Why would that be?

Perhaps the biggest reason is that mold has become very common in buildings and homes. And there are more of those than ever before. When I was born in 1963, there were approximately 189 million Americans. Now there are more than 333 million. More Americans means more buildings in general, which leads to more building problems such as those caused by water damage — which can lead to mold growth.

In addition, scientists have documented rising water levels worldwide; that too can lead to more flooding, more mold growth, and more mold toxicity.