• Original Articles By Dr. Lavin Featuring Expert Advice & Information about Pediatric Health Issues that you Care the Most About

    Mold and Asthma- The Challenge of Environmental Influences on Health

    By Dr. Arthur Lavin
    An excellent study from 2012 took a close look at the connection between homes having mold and people developing asthma.  The study evaluated a number of studies on the subject to give us a sense of the strength of the connection.  Their findings offer much food for thought, including the question of just how do we know when something we fear causes something we fear.  It also, of course, raises the closely related question of how can we tell if something common in our environment really is causing a problem, or not.

    Here is the link to the article:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3492391/

    The words mold and asthma are so charged, it makes sense to start with some basic understanding of what each are before looking at whether mold causes asthma.

    What is Mold?

    There are 4 major forms of life- animals, plants, fungi, and bacteria.  Some would also include viruses in this list, but that is for another day.  Animals and plants are very familiar to us.  When it comes to fungi and bacteria it gets more complicated, because they often are microscopic.

    Bacteria are familiar to us as one of the main forms of life we call germs.  All bacteria live in the world as single cells.  There are no forms of life where bacteria bunch together to create an organism.  Bacteria are the only form of cellular life that has no nucleus in the cell, all it’s DNA floats about the whole cell.  The most familiar bacteria to us are the strep germ and the germs that cause ear infections, UTI’s, pneumonias, and meningitis. But over 99.99% of bacteria are helpful to us and do not cause infections.

    Fungi are a form of life that are somewhere between bacteria and plants/animals.  They are like plants and animals in that their cells have their DNA packaged in a nucleus, and they make energy with little sub-parts within each cell called mitochondria.   In this way, the cell of a fungus is much more like our human cells than like bacteria.  Fungi are also like us in their ability to form vast cooperative unions of cells that create organisms.  Fungi are like animals in that they cannot photosynthesize, they must eat food to live.  They are like plants in that their large organism forms cannot move.

    They reproduce by making spores not seeds which makes them different than plants and animals.

    Fungi come in two varieties.  If they live as single fungal cells they are called yeast.  If they live as multi-cellular organisms, they are called mold.

    Some very large mold colonies create visible structures to make their spores, and these are called mushrooms.

    The word fungus comes from a Greek word, sphongos, which is where the word sponge also comes from.  Many visible fungi, especially their spore creating structures look sponge like, hence why this whole category of life is referred to by a word that originally meant sponge.

    So molds are all fungi, and they are fungi that grow in large multi-cellular clumps.

    Fungi, like bacteria, are nearly everywhere, so there is likely no building completely free of them.  The question is whether if enough mold is present in a home whether that boosts the chances of developing asthma.

    What is Asthma?

    Like mold, asthma is very common.

    In a certain sense, all of us have asthma.  Every lung has the ability to narrow its airways in response to irritating air.  Just think about the example of breathing in a room filled with smoke from a fire.   Nearly everyone in that awful situation will experience difficulty breathing, like trying to breathe through a tiny straw and will start wheezing.  The smoke from a fire is so irritating that the tubes that carry air to the lungs (our airways) get inflamed, they swell, they make tons of mucus, and the muscles wrapping these tubes go into spasm.  These three events- swelling, mucus production, and muscle spasm make the tube narrower which makes air motion noisy (wheezing) and breathing very difficult and labored.

    These are exactly the changes that happen from time to time in the lungs of everyone with asthma, but they happen in far less dire circumstances.  For some these changes happen when pollen is in the air, or when the air is very cold, or when they exercise, or when they get a cold.   These changes are helpful when the air contains dangerous items like fire smoke, but really just a bother when they happen on a nice day or when playing.

    Since all lungs can get inflamed, how do we know when the inflammation is asthma?  The designation is made when the lungs go on to wheeze or cause labored breathing in response to triggers that normally cause no such trouble, recurrently.  So if someone wheezes once with a cold, and never again, this is not asthma.  It must be recurrent.

    The severity of asthma varies by how easily the inflammation is set off and how severe the swelling and inflammation are.   It turns out that since all lungs can be bothered enough to get inflamed, it is also the case that from day to day, over the years, even hour to hour, each of our lungs varies in how easily their inflammation can be set off.   For most of us, the irritation has to be so strong, no wheezing or trouble breathing ever happens.

    For those with asthma, this variation in how easily the lungs get inflamed defines if their asthma gets better over time, or worse.  If someone’s lungs get harder to trigger into inflammation, and if that trend continues to the point they no longer get inflamed we say they grew out of their asthma.

    How could mold cause asthma to develop?

    A mold is a living organism, made up of a very large number of living cells, each of which are fungal cells, as noted above.  These cells make a number of chemicals, and the organism makes seeds in the form of mold spores.   It is mainly the spores, which are spewed into the air, and some of the chemicals which evaporate in the air that can cause the lungs to react.

    Molds live everywhere, there is likely no place you can be where there are no mold spores in the air.  A good way to consider this fact is to think about leaving a piece of bread out, anywhere.  As long as the temperature is above 40 degrees, it will get moldy, anywhere.

    So each of us can have one or more of the several possible reactions to breathing in the spores and chemicals of molds.  The possibilities include:

    • No reaction all your life
    • An allergic reaction for most of your life
    • An allergic reaction at some times of your life
    • A reaction that leads your lungs from changing from not asthmatic to asthmatic
    • A variety of other reactions to molds have been described that have nothing to do with allergies or lungs.

    The question at hand is how can molds do the fourth listed event, changing someone’s lungs from not having asthma to having asthma?

    As noted above, nearly all our lungs vary in the ease with which they are irritated to the point of getting inflamed.   Exposure to mold causes asthma when breathing in the mold spores and chemicals pushes the person’s lungs to be more easily inflamed, even when no mold is around.

    What does the evidence say about how likely mold is to cause asthma to develop?

    Now we come to just how related mold exposure and the development of asthma are.

    Keep in mind, though, that everyone is exposed to mold, at all times.  There very few spots on the planet not coated with mold.

    So the risks here relate to situations when molds really proliferate, not just when they are present.

    With that in mind, the evidence suggests that if there is no evidence for any dramatic proliferation of mold, then the risk of developing asthma from mold is negligible.

    But 4 situations signal that mold may be proliferating, and the more the mold is proliferating, the greater the risk of that place causing asthma to develop.

    Those four situations are:

    1. Water damage to the building.
    2. Visible eruptions of mold on the floors, walls, or ceilings.
    3. A damp feeling in the building.
    4. A musty odor of mold in the building.

    And, it turns out these four indications of mold proliferation cause the risk of asthma to develop in increasing levels, as follows.

    1. Water damage increases the risk of developing asthma by 12%
    2. Visible eruptions of mold increases the risk of developing asthma by 29%
    3. Dampness increases the risk of developing asthma by 33%
    4. A musty odor of mild increases the risk of developing asthma by 73%

    Notice that none of these events are terribly dramatic.  Let’s say the chance of developing asthma is 1 in 20 for young children, which is about right.  That means water damage in your building changes the actual risk of a child developing asthma from 5% to 5.6%.   And dampness raises that risk to 6.6%.  Even the highest risk from a mold situation, having a musty odor, only raises the risk from 5% to 8.6%.

    These are increases, so we have to take mold as a cause of developing asthma seriously.  But in every instance the chance of not developing asthma, remains over 90%, which is very good news.


    1. Mold is a type of fungus.  Fungi are a form of life more like plants and animals than bacteria, but still can exist as single celled fungi (called yeast) or can like us form big groups of cells joined in purpose together (called mold).
    2. Mold creates items that can cause our airways to react, mainly spores and some chemicals.
    3.  It turns out exposure to high levels of mold spores and/or mold chemicals can make the linings of our airways more easily inflamed.  These linings can inflame in anyone, but exposure to mold can make them inflame more easily, and if the ease of inflammation gets bad enough, you have asthma.
    4.  Mold itself is not likely a major cause of asthma, as mold spores are present in every spot in the planet.  But when they proliferate in a building, it now appears clear that exposure can lead to mild increases in the incidence of asthma.
    5.  Mold can make asthma go from happening in about 5% of people to up 5.6 to 6.6, and as much as 8.6% of people.  This is more likely to happen in young children than adults.
    6.  Signs of mold proliferation, in increasing order of mold being present are:
    • Water damage
    • Visible eruptions of mold
    • Damp surfaces
    • Musty smell of mold.

    So, it makes sense to dry out your home to make sure there is no water damage, visible mold growing, damp surfaces, and no musty smell.  Mold can make asthma more likely to appear in children, but even an intense exposure has over a 90% chance of having no impact on developing asthma.

    Mold is yet another reminder that our environment can define our health.

    To your health,
    Dr. Arthur Lavin 


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