Mold In Your Coffee Cup: How To Remove It In 5 Steps

So, what happens if you go to your cupboard, pick your favorite coffee mug, and see that there is mold around the lid and the bottom? Does the cup need to be thrown away, or can it be cleaned and used again?

To clean mold from a reusable coffee cup, take the cup apart completely, then make a solution of distilled white vinegar mixed with tap water in a 1/1 ratio. Spray every part of the cup and leave the vinegar to kill the mold for 5-10 minutes. Rinse clean with warm water and mild detergent.

In this article, I will be explaining step-by-strep how you to clean a moldy coffee cup to make it safe to use again, so keep reading.

mold in coffee cup how to remove

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How to get mold out of coffee cups

In order to remove mold from a reusable coffee cup, you will need to take the following, simple steps.

  1. Take the coffee cup apart completely
  2. Make a solution of one part white (distilled) vinegar to one part tap water in a spray bottle
  3. Liberally spray the coffee mug (and its rubber seal) in the white vinegar/water solution, and leave for five to ten minutes. The vinegar will kill any mold and its spores.
  4. Wash with warm soapy water to remove any mold and vinegar residue.
  5. Ensure the mug is allowed to dry fully before sorting it away for its next use.

Whilst washing your coffee mug with warm water and detergent may be enough to remove any mold visible to the naked eye, if you want to be completely certain that all the mold is dead, white vinegarOpens in a new tab. is an environmentally friendly and highly effective manner to do so.

If you don’t have any vinegar to spare, or you are worried that it may leave a vinegary aftertaste, you also have the option of using baking powder.

Take your coffee mug apart completely (including removing the rubber seal from the lid). Make a simple solution of baking powder and tap water, and again, using a spray bottle, spray it all over every part of the mug (again, including the rubber seal).

Leave the baking powder solution to do its work for at least 5 minutes. Simply wash off any residue from the mug and allow it to dry completely before storing.

How can you tell if it’s mold in your coffee cup?

To determine whether or not you are dealing with mold in your coffee cup or something else entirely, you can look for the following traits.

Mold will usually come in one of several shadesOpens in a new tab., black, blue, green, white, or even orange or red. They will also tend to have a texture that is best described as “fluffy”, “powdery”, “velvety” or sometimes even slimy (depending on the strain). Despite being able to spot these shades and textures, it is still very difficult to tell exactly what strain of mold you are dealing with.

It’s therefore best to always approach mold with caution, as you could well be dealing with a toxic strainOpens in a new tab.. Wearing protective equipment such as a breathing mask, rubber gloves, and eye protection is always advised if you plan to clean or remove it yourself.

To make things even easier, here’s a little table you can use to check whether what you are dealing with in your coffee cup is mold, or just standard marks, stains, and general wear and tear.

Brown marksVinegar/lemon soaks or baking powder pastes applied to the inside of the cup can help to remove stains. Clean the coffee cup using undiluted white vinegar by spraying every part of it and letting it sit for at least 15 minutes, then clean it with warm soapy water and mild detergent.
Slimy deposits Finding anything in your coffee cup that has a slimy texture does indicate some kind of mold growth that could come from many different strains. An indication of black mold (Stachybotrys) growth, this often forms in small, irregularly shaped dots or spot-like patterns that expand rapidly.
Black spots/dots Unless powdery with a musty scent, this is most likely tea or coffee residue that hasn’t been cleaned properly and has been allowed to dryApply undiluted white vinegar to the entirety of the coffee cup, lid, and any other components. If any residue remains after several cleans, discard the cup.
Dark lumpy substance at bottom of cupUnless powdery with a musty scent, this is most likely tea or coffee residue that hasn’t been cleaned properly and has been allowed to dryWash the coffee cup thoroughly, with soaking a good option to loosen up dried residue.
Fuzzy growthAny kind of fuzzy growth in any shade indicates fungal growth, this needs to be completely removed before the cup is safe to use again. Use a white vinegar/lemon juice soak for fifteen minutes to kill the fungi, then clean thoroughly with warm soapy water.
DiscolorationTannins and acids in some drinks will cause discoloration of a coffee cup. In most cases, this has nothing to do with mold and is not a concern.Cleaning the cup quickly after each use will reduce the likelihood of discoloration and staining. Once a cup is losing its color there is little that can be done, however the cup remains safe to use.
White chalky substanceThis is often a buildup of mineral deposits such as calcium or magnesium, seen most frequently in hard water areas. Unless there is a velvety growth that is white and has a musty scent. This is harmless and can be removed. For dried deposits, mix baking soda with a little white vinegar to create a thick paste. Apply it to the affected areas and leave it to sit for 15-20 minutes then rinse clean.

How to prevent coffee cups from becoming moldy

It is much easier to ensure your coffee mug does not become moldy in the first place rather than having to clean it when mold does eventually decide to call it home.

Prevention, in this case, is a simple process, as all you need to do is take away everything mold needs to live. Without perfect circumstances, it cannot and will not grow.

In order to stop mold from growing in your coffee mugs, use the following steps:

  1. Make sure your mug is completely clean after each use
  2. Check the rubber seal every few weeks to make sure it is clean and there are no cracks in the rubber
  3. Ensure once the mug is clean that it is completely dry before being stored
  4. Soak the cup in either white vinegar, lemon juice or baking powder for at least 30 minutes once per month to lessen the chances of growth

Do you need to throw away a coffee cup that has mold in it?

After reading about the potential health hazards caused by accidentally inhaling or ingesting mold and/or its spores, you may think that your coffee mug needs to be thrown away if you find mold growing in it.

This is not always the case, as if only a small amount can be seen, the methods of removal suggested above should suffice in making the mug useable again.

The exception to this rule is if the cup has been infested with mold for a prolonged period of time, (several weeks for example). If this is the case, the mold may have penetrated deep into any crack in the rubber seal and will be significantly harder to remove.

If this is the case, you are better off cutting your losses and purchasing a new coffee mug. You can then use the preventative measures listed above to make sure this is a process you will no longer need to go through.

Can you drink out of a coffee cup that has mold in it?

If we are talking about giving the cup a quick rinse under the tap and then using it again, (or even worse), scraping the mold off and hoping the hot coffee will kill it off, then no, this is certainly not a good idea.

Whilst there are hundreds if not thousands of strains of mold that will cause little to no harm to humans, there are still plenty of strains that can be hazardousOpens in a new tab. if inhaled or ingested.

If a mold feels threatened, it can produce mycotoxins, if these mycotoxins are ingested through drinking coffee out of a moldy coffee cup for example, then gastrointestinal discomfort, headaches, and nausea can result. If the spores are inhaled, then breathlessness is possible, whilst, for allergic asthmatics, a full attack is quite possible.

As a result of the potential for harm, it is never advised to simply scrape the mold off a coffee cup or give it a quick rinse. You should take the time to follow the steps below to completely clean your cup to make sure it is safe to use.

Why do coffee mugs become moldy in the first place?

Mold is not picky as to where it lives, as long as the circumstances are correct, mold will grow pretty much wherever it can, and unfortunately, your favorite coffee cup is no exception to this.

Mold only needs a few things in order to thrive, these are:

  • A source of nutrients
  • A source of moisture
  • An ambient temperature between 60-80 degrees Fahrenheit
  • A lack of natural sunlight

As you can probably see from the list above, a coffee cup left in a rucksack or handbag on Friday, then forgotten about until Sunday will very easily provide everything that mold needs.

It can feed off the minuscule particles of coffee grounds, or any leftover sugar or syrups left in the cup. The moisture comes from any remaining coffee or steam that condensed on the lid, and with the lid left on, there is no danger of sunlight. It has also probably been left in a comfortably warm room of the house all weekend, which gives mold the perfect opportunity to grow.


Mold in portable coffee mugs is fairly common, but fortunately easy to resolve. The molds found growing within them have the potential to cause health issues if consumed in great enough quantities. Lemon juice and undiluted white vinegar are excellent mold killers, and leaving them on the growth or stain for fifteen to twenty minutes will kill the mold and remove most stains. If this does not work on the first go, you can repeat it as many times as necessary. If the stain remains or the growth returns frequently, purchasing a new cup may be required.

Over to you

I really hope this guide has helped you to effectively clean out a moldy coffee cup and answered some of the questions you may have had about why it happened in the first place. But now I’d like to turn things over to you, have you ever drank from a moldy coffee cup? Have you tried any of the methods I’ve mentioned today or do you have any that you think should be added to the list above? If you do, I’d love to hear about them, or if you have any questions at all, please feel free to leave a comment below and I’ll get back to you.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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