IMHO, it is nothing short of a miracle deodorant! I've seen many recommend M9 as the de facto ostomy deodorant. I finally bit, and not quite for a week of use yet. I'm convinced it works! It doesn't have any smell, so it's not a cover-up. This got me wondering how this is working so well. So, I asked the intertubes what the ingredients are doing.
Here's a summary of what is known (and what is uncertain) about M9 Odor Eliminator's effectiveness, mechanism, advantages/limitations, and how it stacks up against alternatives:
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What is known / what evidence exists
Manufacturer claims & product descriptions
The maker, Hollister, states that 4–12 drops of M9 should be put into an emptied ostomy pouch at each change (or after emptying) to help eliminate odor rather than simply mask it.
It's marketed as “highly effective at eliminating smells” when placed in the pouch.
It is intended for both colostomy and ileostomy use.
The spray form of M9 is also marketed to neutralize odors in ostomy pouches, urinary catheters, and similar devices.
The product is presented as “neutralizing” odor (i.e., interacting with odor compounds chemically) rather than merely “masking” or covering it with fragrance.
The safety/compatibility claims include: “latex-free, non-acidic, water-soluble, non-flammable, safe for urostomy bags and tubing.”
So, the evidence from the manufacturer is consistent: M9 is used widely, and the formulation has been around and marketed for many years. The ingredient list (especially the copper salt) is known and transparent.
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How it likely works (mechanism)
Given that M9 contains disodium cupric citrate (a copper complex) as its active ingredient, here's a plausible (and commonly cited) mechanism of action:
Many fetid odors in waste (and therefore in ostomy pouches) come from volatile sulfur compounds (VSCs) (e.g., hydrogen sulfide, mercaptans) and amines produced by bacterial breakdown of proteins.
Copper ions (Cu²⁺) can oxidize or bind with sulfur- or nitrogen-containing compounds, neutralizing them or converting them into less volatile or less odorous species.
The acidic environment (citric acid) helps maintain copper in a soluble, active ionic form and may help protonate or destabilize sulfide/amine species.
Preservatives (parabens, phenoxyethanol) keep the formulation microbiologically stable so that the copper remains active over time and the solution doesn't degrade or grow microbes.
Thus, rather than masking smell, it chemically interferes with the offending molecules.
Because of this chemical action, M9 (if used properly) can have longer-lasting odor suppression compared to simple fragranced deodorants.
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Strengths & advantages
Longer-lasting odor control: Because it reacts with odor-causing compounds (rather than just masking), control may last for the entire wear time of the pouch.
Less fragrance smell: As it's “unscented” (or minimally scented) and acts chemically, users who dislike strong perfumes may prefer it.
Compatibility: The product is designed specifically for ostomy pouches; the manufacturer claims it is safe for use with pouch materials and urostomy systems.
Ease of use: Only a few drops are needed — it doesn't require bulky inserts or tablets.
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Limitations, uncertainties & things to watch out for
Lack of independent clinical studies (public domain) — I did not find rigorous peer-reviewed trials verifying how effective M9 is versus placebo or versus other odor control methods. The publicly available documentation is dominated by manufacturer and reseller claims.
Effectiveness depends on pouch conditions: If the pouch is not emptied frequently, bacterial load or waste volume may overwhelm the capacity of the copper to neutralize odor.
Copper saturation/depletion: Over time, the copper ions might be “used up” (i.e., fully reacted) and lose effectiveness, especially with heavy odor burden.
Parabens/preservatives: Some people are sensitive or wary of parabens; though they are used in very low quantities, they are present.
pH/environment constraints: If the internal conditions (pH, moisture, presence of interfering substances) stray too far, the ability of copper to remain active may be reduced.
Not a substitute for proper pouch hygiene: It helps with odor but does not replace regular emptying, cleaning, or pouch changes.
No effect on strong external odors or leaks: If stuff is leaking or gases escape through openings, M9 can't fully prevent external smell.
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Comparison to other odor control options
Here are a few alternatives and how M9 stacks up:
Alternative Mechanism Pros vs M9 Cons vs M9
Charcoal or activated carbon filters in pouch vents Adsorption of gaseous odor molecules Passive, no chemicals, no need to add drops Can saturate / become less effective; doesn't act deep inside waste slurry
Fragranced deodorant sprays/sachets/beads Masking odor with fragrance Strong immediately; familiar smell Doesn't reduce underlying odor, needs reapplication, can be overpowering
In-pouch odor absorbents or tabs Chemical absorbers (e.g., zeolites, perlite) Some act without needing a drop addition Bulkier; may interfere with waste flow or visibility
Biological/enzyme products Enzymes that break down odor-causing compounds Can act over time and “clean” microbial residues Usually slower/less potent; stability of enzymes is tricky
Frequent pouch changes and good hygiene Physical removal of odor source Fundamental, no chemicals Inconvenient to change so often; odor builds quickly between changes
In summary, M9 (copper-based) offers a chemical neutralization approach that complements these alternatives: it can work synergistically with filters or good hygiene, rather than wholly replacing them.
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My assessment & recommendation
Given what's known, I believe M9 is likely reasonably effective for many users in real-world ostomy use — especially for mild-to-moderate odor loads — but it is not a “magic cure.” Its strength lies in its chemical odor neutralizing action, but its effectiveness will depend considerably on conditions (how full the pouch is, bacterial load, how often it's emptied, etc.).
