As a homebuilder dedicated to building healthy homes, I tend to read construction product labels. Adhesives, sealants, paints, you name it.

This week, I was using this product (above), and noticed these familiar words on the label:

Once sensitized, a severe allergic reaction may occur when subsequently exposed to very low levels.

SIKA Pro Select Construction Sealant (on label)

The warning is also on the Safety Data Sheet for this product, too (in green):

This isn’t unusual, actually. Many, many products have this warning.

What does this mean? It means the body may have no reaction when exposed, at first.

But over time, immune/allergic reactions can occur, with more and more intensity — even by smaller and smaller levels of exposure.

And of course, anyone who has suffered from environmental illnesses ( example: MCS; Multiple Chemical Sensitivities) — will recognize that pattern.

If you don’t know, you might ask: “What is Multiple Chemical Sensitivity?“

“MCS symptoms are reported to occur following exposure to concentrations of chemicals that are below the levels that are typically considered harmful for the general population.”

https://www.mass.gov/info-details/multiple-chemical-sensitivity

If you’ve ever known someone who couldn’t tolerate being around fragrances — or cleaning chemicals, or mold (or others) — they probably had some level of MCS.

Obviously many construction products are toxic. Clearly, the industry recognizes — and warns — they can cause sensitization.

After all, the warnings even indicate increased cancer risk by contact — and even by inhalation.

“Group 1: Carcinogenic to humans” and “known to be human carcinogen” are ubiquitous on construction labels. The product label I used yesterday: “Carcinogenic via inhalation.”

But what about these environmental sensitivities — to things like fragrance, or mold? Just how toxic is something like mold? Here’s what we know: Mold can be decidedly toxic.

Mold’s noxious VOC’s are known, scientifically, as “mycotoxins.”

“Mycotoxins are secondary metabolites produced by microfungi that are capable of causing disease and death in humans and other animals. [Some] have been implicated as chemical warfare agents.”

https://pubmed.ncbi.nlm.nih.gov/12857779/ (National Institutes of Health)

But there’s a huge difference in the way people are exposed to
toxic construction products and mold mycotoxins:

Mold is more sneaky: it’s released slowly, and continually each day — rather than all at once, with a noticeable, heavy smell. It likely will take more time to cause sensitization.

It may take 1-6 months, or even years to become sensitized.

But sensitization is where it begins. First, to one toxic compound — perhaps mold, or even cleaning chemicals, or after extended antibiotic use. Then the body starts reacting more aggressively to smaller and smaller exposure levels.

In my experience — both working with hundreds of people and in my own journey — I see mold as a common “gateway drug” that starts sensitization — in part due to its widespread prevalence, and the fact that we spend so much time in our homes or workplaces.

In other words, is it possible that mold is a sensitizer? That it’s a toxin that begins or expedites the sensitizing process?

Many people are battling sensitivities to fragrances and chemicals, not realizing mold’s toxic mycotoxins — always in the background — could be sensitizing their body.

It’s not just mold, though. The science of “sensitizers” is real, and progressing.

Sensitization — as a concept — wasn’t invented by construction companies. No, the topic has been studied for decades in the scientific literature.

Notice what happened to Kate McKnelly, researcher at UC-Irvine. Her story has shed light on how chemical compounds can act as “sensitizers” — effectively sensitizing the body to other compounds in the environment.

“If you look at a chemical label and it says ‘Flammable,’ then you know to be really careful. Or if it’s a carcinogen, then you know it can cause cancer. You have a good grasp on what those words mean,” McKnelly says. “Sensitizer is a more nebulous term.”

Kate McKnelly, PhD

What’s showing up in the scientific literature is that homes that contain cleaning chemicals can sensitize the body’s immune response.

Exposure to specific household cleaning products may be one factor that is able to affect susceptibility to allergic sensitization.

https://pubmed.ncbi.nlm.nih.gov/22953700/

The real-world implications for thousands and thousands of people with “multiple chemical sensitivities” around the globe? Potentially life-altering.

“The implications for chemical sensitivities can be devastating to a person’s livelihood.”

https://www.hsph.harvard.edu/hoffman-program/2016/01/28/are-you-allergic-to-your-job/

It’s not magic when sensitization happens. Here are some other variables that contribute to sensitization.

“Acute infectious diseases may produce some of the same symptoms also.”

https://www.ncbi.nlm.nih.gov/books/NBK234810/

Viruses — such as Epstein Barr — can cause sensitization.

A gut infection, even bacterial, can be a cause. Oftentimes, antibiotics prescribed for the infection can make this worse — perhaps, in part, because healthy microbes are wiped out.

And of course, mold is a fungus — it’s a microbe capable of infection. Living in a moldy space means breathing in and swallowing spores that have the capability of living in the gut.

There are about 10-20% of almost any population which show greater “sensitivity” to irritants, which is usually organ (e.g., eye) specific, by responding at lower doses.

https://www.ncbi.nlm.nih.gov/books/NBK234810/

Chronic inflammation — an immune response, the natural result of chemical sensitivities — directly harms the liver and kidneys, specifically. Downstream, inflammation also deprives cells of needed energy from food and nutrients. The gut microbiome is typically affected by chronic inflammation, as well.

If you are struggling with environmental illness — or someone you know is, despite sharing similar living arrangements — genetics could be a factor.

Siblings, children, parents — all have different DNA from each other. Small, minor mutations happen in everyone’s genetic code. And science has identified some very specific mutations that cause the body to detox more slowly.

There are also host susceptibility factors, including genetic predisposition, which will play a role in sensitization and in disease manifestation (Turner-Warwick, 1978; Gregg, 1983). 

https://www.ncbi.nlm.nih.gov/books/NBK234810/

Genetic variability… may affect the function of detox enzymes, thus impacting the body’s sensitivity to toxic substances of endogenous and exogenous origin.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8876337/

Ultimately, though, our world is complex. There are usually multiple inflection points that can lead to sensitization.

At any inflection point, the body can become sensitized. Perhaps we’re genetically more prone to a powerful mast cell (immune) response, but we don’t have to be for this to happen.

Here’s the point: The body can become sensitized to a chemical compound. And that sensitization, if allowed to continue — if we’re chronically exposed — can expand, leaving us sensitive to more and more things.

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