nontuberculous-mycobacteria-showerhead

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A nontuberculous mycobacteria showerhead question usually comes after reading that these bacteria can cause lung disease. The person searching wants to know three things: whether a showerhead can hold nontuberculous mycobacteria (NTM), whether shower spray can carry them into the lungs, and what to do about it. Two peer-reviewed studies answer part of that. Both found NTM in showerhead biofilm, and one found NTM in the air during a shower. Neither study measured illness in people who used those showers, and neither source gives a home cleaning method that removes NTM.

Quick answer

A pilot study sampled five showers in five homes on O’ahu, Hawai’i. It reports that “one in five homes (20%) showed NTM recovery from shower and air samples.”
In that pilot, the air after a shower sometimes held NTM. Running a dehumidifier in the shower reduced the NTM recovered from the air in the homes where NTM had been found. The authors call this a possible intervention that needs larger trials.
A larger study of household plumbing from patients with NTM disease found NTM in 28 percent of samples. In 7 of the 17 patients whose isolates could be compared, the patient’s strain matched a strain from their home plumbing.
Neither source gives a cleaning method that removes NTM from a showerhead in a home. The sources do not say how to do it.

Who the two studies sampled

The pilot study is the smaller of the two. Its authors describe the design in plain terms: “A total of five showers from five O’ahu non-patient homes were included in this study.” The homes were sampled twice, in December 2022 and again 16 weeks later in April 2023. Homes did not have air conditioning, and bathroom exhaust fans were turned off during sampling. Showers were not used for 12 hours before sampling.

At each home, swabs collected showerhead biofilm. Air samples were collected about 6 feet below the showerhead before the shower ran and again after an 8-minute shower. Humidity was recorded every minute during the shower. A commercial dehumidifier was then placed in the shower stall until relative humidity dropped by 10 percent, and the air was sampled again. Each sampling event produced 50 culture plates.

The larger study comes from a different group of homes. Its authors describe it as a pilot study of household water systems. Samples were received from 31 patients across the United States and Canada, and the study covered 37 households and 394 samples. The sampling was done because the patients had NTM infection. The study therefore describes households connected to people with NTM disease, not a random set of homes.

What the pilot found

NTM were uncommon on the showerhead surfaces in the pilot. Of the 50 culture plates from the first sampling event, “Of the 50 culture plates, four were NTM positive (8%).” The NTM isolated were species the authors name as Mycobacterium chelonae, M. porcinum, and M. intracellulare. The first sampling event found M. chelonae on the showerhead in one home. The text reads: “M. chelonae was detected in one (House 1) out of the five (20%) showerheads sampled.”

The air results are the part that matches the question most closely. In the first event, the same home that had NTM on its showerhead also had NTM in the air after the shower. The authors write that “M. chelonae was recovered from the air post shower in House 1, despite no detection of NTM in shower air before the shower was turned on for 8 min.” In the same home, after the dehumidifier ran, the air was clear. The authors write that “the air sample collected after House 1 shower stall was dehumidified was devoid of M. chelonae or other NTM.”

The second sampling event used a culture medium designed to reduce mold, because mold had grown on many plates in the first round. In that event, M. intracellulare appeared in one home’s showerhead biofilm and in the post-shower air. After dehumidification, it was not detected in the air. The authors summarize the two rounds this way: “Overall results from two sampling periods suggest reducing RH in showers lowers NTM transfer from showerhead biofilms to the air after a showering episode.” The word “suggest” matters here. Five homes is a very small number.

The authors also flag a limit on the air results. The authors note that mold “may have interfered with efficient NTM recovery” in the air samples. Mold on the plates may have hidden some NTM, so the air results could understate what was present.

What the larger household study found

The larger study looked at whether household plumbing matched the NTM infection in the patient. Its authors report that only 28% of household samples yielded NTM. Samples included water, biofilm, filter and soil material. Its sampling instructions covered biofilm and sediment from water taps and showerheads, collected by swab. Of 37 households, 22 (59 percent) had at least one NTM-positive sample.

The match is the strongest claim in the study. Of the 17 patients from whom isolates were obtained, the authors write that “Seven (41%) of the 17 patients from whom isolates were obtained were infected with an NTM strain having the same DNA fingerprint as at least 1 NTM isolate from their household plumbing.” That is a match between a patient’s strain and a strain found at home. The authors conclude that “The data document the relevance of household water as a source of NTM infection.” A DNA match is evidence that the same strain was present in both places. It does not establish how any one person was infected, and the study does not claim to.

The study also looked at what differed between homes. Households whose water heater was set below 50 °C were more likely to have NTM than households set above 55 °C. The table lists the thresholds as below 125 °F (50 °C) and above 130 °F (55 °C). In the lower group, NTM were found in 17 of 20 households (85 percent). In the higher group, NTM were found in 6 of 15 households (40 percent). The authors report a relative risk of 2.125 and a p value of 0.0107 by Fisher exact test. The text also says that “the data from this pilot study with its relatively small sample size suggest that water heater temperature and water source could be factors influencing NTM presence.” The word suggest carries the weight here, and the study does not examine a change in water heater temperature.

The text of the study gives the heater thresholds in degrees Celsius with a unit error (“125°C”). This guide follows the table, which lists the Fahrenheit and Celsius values together.

Who the studies describe as at risk

NTM disease can take several forms, but the sources focus on lung infection in people with specific health conditions. The larger study states that “Infections occur in immunodeficient (e.g., HIV/AIDS) and immunosuppressed (e.g., cancer and transplant) patients and nonimmunosuppressed persons with the classic risk factors for mycobacteria infection.” It also says that “The major manifestation of NTM infection in the immunocompetent host is pulmonary disease.” The same paper names cystic fibrosis and some genetic and enzyme conditions as predisposing factors. It also states that “Elderly, slender women lacking any of the classic risk factors for NTM disease are also at risk for NTM pulmonary disease.”

The pilot study describes the danger the same way. Its introduction says NTM “form biofilms on household piping and showerhead surfaces that are aerosolized and inhaled to cause chronic lung infections in susceptible individuals.” The phrase “susceptible individuals” is the authors’ own. Neither study measured how often healthy people in ordinary homes develop NTM disease after showering, so the sources do not give a number for that group.

If you have a weakened immune system, a lung condition, or cystic fibrosis, talk to a doctor before changing anything in your routine. This guide does not give medical advice. A doctor who knows your history is the right person to ask whether shower exposure matters for you.

What the sources say about reducing exposure

The sources offer a few suggestions. Most are presented as untested. The pilot’s introduction states that “Other suggestions to reduce NTM exposures are anecdotal and include avoiding long showers or using showerheads with small pore sizes and avoiding dust inhalation.” The same paper also says “Studies show raising hot water heater temperatures, disinfecting showerheads, and using UV filtration systems or point of use filters also reduce NTM.” Those statements point to other studies that this guide did not open, so they are reported here only as the pilot describes them.

The pilot also warns about humidifiers. The authors write that “ultrasonic humidifiers generate high density aerosols that are rich in NTM” and should be avoided. The larger study suggests that “persons infected or at risk for NTM disease” might consider higher water heater temperatures, since it found fewer NTM in homes with hotter heaters. Changing a water heater setting is work for a licensed plumber or the equipment maker. This guide gives no steps for it.

The cetylpyridinium chloride treatment named in the pilot is a laboratory step. The authors describe the swabs as “microbiologically processed using cetylpyridinium chloride (CPC) decontamination methods,” so the treatment was applied to samples in the lab, not to showerheads at home. No source opened for this guide gives a cleaning method for a home showerhead.

How we chose

This guide uses the two sources that could be read in full and that address NTM in showers or in household plumbing. Other candidate papers in the research folder returned no usable body text on NTM in showers, or they covered a different organism or setting, so they are not used. Both sources were opened on 2026-10-28. The pilot’s sampling dates are December 2022 and April 2023. The larger study’s household samples were collected between 2007 and 2009, as the paper’s table states.

Each claim in this guide is either a direct quote from one of these sources or a number taken from its tables. Where a sentence is the guide’s own summary, it does not add a fact beyond what the source states.

What the sources do not say

Neither source reports an illness rate for people who shower in ordinary homes.
Neither source gives a home method to clean or disinfect a showerhead that removes NTM. The pilot’s suggestion to disinfect showerheads is presented as coming from other studies, and no method is described.
The pilot tested five showers in five homes on one island. The authors state that these samples “preclude making generalizable conclusions” about the role of humidity in showers.
The larger study’s households were connected to patients with NTM disease. The sources do not say whether the same results would appear in unrelated households.
Neither source evaluated a shower filter or a showerhead design as a way to reduce NTM in showers. The pilot mentions small pore sizes only as an anecdotal suggestion.

What we could not verify

The studies that the pilot cites for its claims about raising heater temperatures, disinfecting showerheads, and UV or point-of-use filters were not opened for this guide.
The claim that Hawai’i has the highest NTM lung disease prevalence in the United States comes from the pilot’s introduction. It is a citation to another source that this guide did not open.
Whether the 2023 air results would repeat in a larger set of homes. The authors call for “large-scale, prospective case-control community trials” before drawing firm conclusions.
Whether a dehumidifier in a shower changes NTM exposure over a year, or whether it affects illness at all.

FAQ

Can a showerhead carry nontuberculous mycobacteria?

Yes, the pilot found NTM in showerhead biofilm in one of five homes. In the larger study, swabs from taps and showerheads were among the household samples. Across all samples, NTM were found in 28 percent. The results come from small, specific groups of homes, so they do not show how common NTM are in every showerhead.

Does a shower cause NTM lung disease?

The sources do not show that a shower caused disease in any person. The larger study found matching strains in 7 of 17 patients, and the authors describe household water as a source of NTM infection. The pilot found NTM in the air after showers in one home. Neither study followed people over time to see who became ill.

Does chlorine make showerhead NTM worse?

The larger study states that “residual disinfectant selects for disinfectant-resistant NTM.” That statement describes the water in general, not shower filters or showerheads. None of the sources opened tested a chlorine level against NTM in showers, so the guide does not make a claim about chlorine and showerheads.

What cleaning method do the sources recommend?

None of the sources gives a home cleaning method for NTM in a showerhead. The pilot lists disinfecting showerheads as a reduction method, citing other studies, but does not describe how. The CPC step in the pilot was used on samples in the laboratory.

Should I be worried about my shower?

The sources describe risk mainly for people with weakened immune systems, certain lung conditions, cystic fibrosis, and some genetic or enzyme conditions. They do not give a risk estimate for healthy people in ordinary homes. If you fall into one of the higher-risk groups, talk to a doctor.

Does lowering humidity in the shower help?

In the pilot, running a dehumidifier in the shower reduced the NTM recovered from the air in the homes where NTM had been found. The sample was five homes, and the authors call the result a suggestion that needs larger trials. The study did not measure whether lower humidity reduces illness.

Talk to a doctor

NTM disease is a medical condition. If you have a weakened immune system, a lung condition, or cystic fibrosis, or if you have symptoms such as a cough that does not go away, talk to a doctor. Do not change your treatment or medicine based on this guide. A doctor can tell you whether household water is worth discussing for your situation.

Bottom line

NTM can be found in showerheads and in shower air, according to the two sources. The evidence is limited: one small pilot in five homes and one household study of patients’ homes. The sources connect NTM disease to specific health conditions and do not give a risk estimate for healthy people in ordinary homes. No source gives a home cleaning method, so this guide does not provide one.

Sources

BMC Research Notes, PMC10976743 (pilot study of showerhead biofilm and shower air in five Hawai’i homes). https://pmc.ncbi.nlm.nih.gov/articles/PMC10976743/ (opened 2026-10-28)
Emerging Infectious Diseases (CDC journal), PMC3166028 (household plumbing study of NTM patients’ homes). https://pmc.ncbi.nlm.nih.gov/articles/PMC3166028/ (opened 2026-10-28)