Is your shower making you sick?

Despite my best efforts for this not to come across as fearmongering, it's probably going to look like it because the reality is largely unseen and Charash Renovations is a for-profit corporation. If we can set those two things aside for the sake of understanding, I think you might find the information enlightening and it may reveal a potential cause for sickness lurking within your shower.

First, some basic building science. When it comes to water vapor and temperature, hot goes to cold and wet goes to dry. That is, warm air wants to move toward cool air and moist air wants to move toward dry air. Now, let’s think about the shower environment. Unless you are one of those crazy cold shower people, you like a hot steamy shower. During the five to ten (or 30 for those teenagers out there) minutes you’re in there, you are creating a condition in which that hot and moist air really wants to go somewhere. That somewhere is where it is the relatively dryer and cooler materials and air behind the tile. Tile and grout and the mortar holding it all in place is porous. Yes, even porcelain (though barely). Yes, even if you sealed it. Remember, we are talking about molecular scales.

Traditionally built tiled showers are built with cement based materials behind the tile which are high-mass, highly porous materials that can hold a large volume of water. The system under the tiled floor is actually designed to saturate. If you are showering every day, and I hope you are, then this material never has sufficient time to dry out. That means you have a constantly damp material under your shower floor tile and such a material will grow mold. Wet material can grow mold in as little as 48 hours and most showers don’t show outward signs of structural degradation for 10 to 15 years.

The conclusion is obvious. If the material behind your tiles cannot dry out between uses, it is almost certain that you have a mold farm behind your walls and under your floor. Now, you turn on your bath fan because it is so humid in there. Somewhere between 25 and 150 cubic feet of air per minute is being pulled out of that room. In doing so, you are creating a vacuum in the space, so it wants to suck from adjacent areas. Air will take the path of least resistance, so some of that make up air will come from adjacent rooms, but when that is insufficient it will also pull from leaks and pores in your walls and ceilings. Now you are pulling that mold back through your grout, into your bathroom and into your lungs.

The science behind this is deep and complex, so it must suffice to say that if you have a traditionally built tiled shower (and you do if the original builder built it), then you most certainly have mold behind the tile. Not everyone is sensitive to mold, but a significant number are. They often present with the expected symptoms, such as runny nose and watery eyes, but many present with unexpected symptoms such as anxiety and depression.

According to Toxicology and Industrial Health (Empying, 2009), “Human exposure to molds, mycotoxins, and water-damaged buildings can cause neurologic and neuropsychiatric signs and symptoms. Many of these clinical features can partly mimic or be similar to classic neurologic disorders including pain syndromes, movement disorders, delirium, dementia, and disorders of balance and coordination.”

And according to an article in Discover Toxicology (Abia, 2025), “The most common mycotoxins aflatoxin B1, ochratoxin A, T-2 toxin, deoxynivalenol, zearalenone, and fumonisin B1 induces neurotoxicity via different mechanisms including disruption of neuronal signalling pathways, DNA damage, epigenetic modifications, impaired neurogenesis, oxidative stress, autophagy, disruption of neurotransmitter systems, mitochondrial dysfunction, and neuroinflammation. Exposure to mycotoxins has been associated with cognitive impairments, learning difficulties, behavioural abnormalities, and neurological disorders.”

Especially if you have very young children in the home, you need to consider the potential effect of a traditionally built tiled shower in your home as a source for mold. I would highly recommend a mold test through a reputable mold remediation company; however, do not let them rebuild anything. Their expertise is in testing and removal. If they just rebuild it in the same way, you can expect the same result in the not too distant future. If you have concerns about mold in your shower or bathroom, please reach out to us at Charash Renovations. Our desire is to give you a healthy, low-maintenance bathroom that will be a source of enjoyment, not disease, for generations.

Empting LD. Neurologic and neuropsychiatric syndrome features of mold and mycotoxin exposure. Toxicol Ind Health. 2009 Oct-Nov;25(9-10):577-81. doi: 10.1177/0748233709348393. PMID: 19854819.

Abia, W. A., Foupouapouognigni, Y., Nfombouot, H. P. N., Ngoungoure, L. V. N., Ntungwe, E. N., Salah-Abbès, J. B., & Tchana, A. N. (2025). A scoping review on mycotoxin-induced neurotoxicity. Discover Toxicology, 2(1), 1.