The idea that Multiple Chemical Sensitivity (MCS) is an anxiety disorder is one that just won’t go away, despite the abundance of evidence to the contrary. I wrote a post about some of the studies demonstrating biological causes 11 years ago and I’m going to revisit the topic today and briefly discuss some of what we’ve learned since then. Some of these mechanisms overlap and work together, but I’ll separate them for the sake of clarity.
Mast cells may be involved. A 2021 study notes that our understanding of mast cells and their ability to cause inflammatory and allergic responses has grown rapidly in the past decade. Mast cells are the body’s first responders, reacting quickly when they perceive a threat. They respond to different threats in specific ways, releasing histamine in response to a bee sting, for example, and different mediators in response to chemical exposures. The authors note that mast cell activation appears capable of explaining chemical, food, and drug intolerances that follow exposure to a wide range of xenobiotics (chemicals not naturally produced by the body). After comparing patients with Mast Cell Activation Syndrome (MCAS) and Chemical Intolerance (CI) or Toxicant Induced Loss of Tolerance (TILT) they note that “as the likelihood of patients having MCAS increases, their likelihood of having CI/TILT similarly increases, to a near-perfect correspondence at the high ends of these scales.”
Stimulation of the aryl hydrocarbon receptor (AHR) and the NMDA receptor may be part of the process. If you’re interested in this fascinating but somewhat complicated topic, block off some time, put on your thinking cap, and watch the brilliant and tireless Bob Miller (who I’ve worked with for years) explain it in a recent video.
The AHR is a unique environmental sensor that, depending on what it binds with, can act in either a pro-inflammatory or anti-inflammatory manner. Exposure to certain chemicals and other things, including mycotoxins from mold, can lead it to initiate a process that stimulates mast cells. The process Miller describes can also involve an increase in intracellular calcium. When the balance is off between the calcium outside and inside our cells, it can cause significant problems, including damage to the immune and central nervous systems.
Chemical exposures can activate the cell danger response (CDR). The CDR is triggered when threats in the environment overwhelm the cell’s capacity to meet them. A 2020 article notes that people can be resistant to exposures, but then become vulnerable to reactions after a predisposing event. The author adds that in sensitive people, “whose cell danger response has been primed by a perfect storm of previous chemical, microbial, physical, and/or psychological stresses,” exposures can cause significant and long-lasting reactions. In an earlier publication, the author noted that an understanding of the CDR helps us reframe old ideas about disease development for a wide range of conditions, including “food and chemical sensitivity syndromes.”
Endocrine disrupting chemicals may be part of the picture. In a wonderful presentation that’s well worth watching, Dr. John Molot notes that traditional toxicology has always said that “the dose makes the poison,” so the field has had trouble understanding how people with MCS can react to such low levels of chemical pollutants. We now know, however, that some chemicals can act at very low doses, due to the way they interfere with the functioning of hormones. “Hormones” doesn’t just mean the reproductive ones. We have over 50, including serotonin, insulin, and cortisol, and they have wide-ranging effects.
One of the ways that certain chemicals confuse our body is that they bind to the cell receptors where natural hormones are supposed to fit. Molot states, “If a foreign chemical has an affinity to bind to a receptor, it can stimulate it and initiate changes in cell signaling and function. Even very low, but repeated doses can stimulate the cell to produce even more of these receptors (this is called upregulation) which results in an increased ability to detect the chemical and increased responses by the cell to the perceived message.”
Transient Receptor Potential (TRP) channels may play a role. Molot notes that the 2021 Nobel prize was won by David Julius and Ardem Patapoutian for their discovery of this family of receptors. TRPs respond to stimuli, including from chemicals, and transmit corresponding signals to cells. Molot points out that there is robust evidence that these receptors can become sensitized. In fact, he points to 20 studies that show that two particular TRPs are sensitized in patients with Multiple Chemical Sensitivity.
There seems to be a strong genetic component. In particular, when people have a genetic profile that makes it harder for them to detoxify toxic compounds, they are much more likely to develop MCS. In my 2012 post I mentioned a study that found that women with variants in two genes associated with detoxification were over 18 times more likely to have MCS. In his video presentation, Molot points to seven published papers demonstrating that patients with MCS have more genetic variants related to poor detoxification than people without the condition do.
In 2015, a fascinating study was published that indirectly points to the genetic component and detoxification challenges. The authors found that mothers with chemical intolerances were three times more likely than others to report having a child with autism. One possible explanation is that the children inherit the genes that make them poor detoxifiers from their mother and the buildup of toxins contributes to the development of autism. Another possibility is that even without inheriting the problematic genes, the children may simply be born with a higher toxic load because mothers unfortunately share some of their chemical body burden with their developing children. Whatever the mechanism, it seems unlikely that the correlation would exist if MCS were simply a psychological condition.
I often wonder why the “MCS is anxiety” narrative has such deep roots despite all the contrary evidence. As I’ve noted many times, part of the reason is that there’s been a very deliberate disinformation campaign which has been largely successful. I think it’s more than that, though.
I think there’s a belief that anxiety is something that people can think their way in and out of, and if we believe that people’s problems are on some level their own fault, we can assure ourselves that we’ll never find ourselves in their shoes. In the case of MCS, this also means that we don’t have to make the lifestyle changes that could make a difference. The reaction is understandable, but dangerous.
Yes, there’s a genetic component to MCS, but whether or not you have a profile that puts you at higher risk, you aren’t immune. A 2018 study found that the prevalence of MCS increased over 300% in a decade. And, of course, chemical exposures are linked to a wide range of other health effects, including cancer. Take care of yourself. Take care of those of us with MCS. Please make the changes that will give us all a healthier future.