Do mothballs expire? How to know when to replace them

Picture of White Mothballs on Pink Background With Text "Do Mothballs Expire?" Overtop

Growing up, my grandmother’s house wreaked of mothballs; I have a feeling some of you reading have one mothball scented memory or two. Thinking back, did she ever have to change them out?

Generally, most quality mothballs have an expiration date of up to two years while sitting in the bag, unopened. The exact expiration date will be listed on the bag. While in use, most mothballs can last up to two to three months before beginning to dissolve, dependent on temperature and humidity.

So, you’ve probably got more questions after that. What happens when they expire and do they lose their potency? We’ve got a few answers for you.

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An important note regarding the proper use of mothballs

First things first for our United States readers, please don’t use mothballs other than how they’re directed for use on the label.

Mothballs generally contain an active ingredient known as naphthalene. According to the National Pesticide Information Center, when the vapor of a mothball releases naphthalene, it may be toxic to humans and pets.

So that scent you’re smelling of mothballs may actually be toxic.

The National Pesticide Information Center lists that mothballs’ proper use is to eliminate clothes moths by placing mothballs in tightly closed spaces. This usage will prevent pesticide fumes from leaking into the air of your living quarters for a prolonged period.

Putting them in this tightly confined container is going to help prevent the scent from leaking out into your living room, garage, home, or wherever you’re thinking of putting them and also make them pretty hard to reach by anyone else.

To add, naphthalene mothballs are banned in Europe, as well as China, in case you were wondering about that.

And of course, please read any further safety and handling information on the bag of any mothballs that you get.

OK, onto the good stuff now.

Do mothballs lose their potency when they expire?

Mothballs absolutely lose their potency when they expire. When sealed in the bag past the expiration date, their scent won’t nearly be as strong. When their smell isn’t as strong, mothballs are less effective.

A mothball that is being used and has been exposed to air will begin to dissolve around 2-3 months when used properly and can take double that amount of time to fully dissolve. Once mothballs start to dissolve, they usually can still be effective, but less effective as time goes on.

For mothballs that are brand new and unopened from the manufacturer, most quality mothballs will stay good up until their expiration date, which is generally two years. Each mothball manufacturer will have a different expiration date listed on their label, so be sure to check for it.

Let’s take scenario A.

You’ve got a brand-spankin’ new bag of mothballs that you plan on using correctly to fight the good fight against moths.

Once you get the bag of mothballs and after reading the instructions, there should be an expiration date printed somewhere on the bag. This is the date that your mothballs will be good for while they are in the bag, unopened. NOT after being opened.

You may only need to use a few mothballs for your use and would like to save the rest for a later time.

After doing so, you can seal the bag with some tape or clip, and use gloves to store it in an airtight container out of reach, so that no one can grab them except for you.

Once you store them like this, the mothballs should be good for use until their listed expiration date, since you’ve stored them properly.

The mothballs you are using and presumably are touching your clothing in a tightly sealed container will still begin to dissolve around 2-3 months. However, they will still be effective for up to 6 months and possibly longer.

If you’re worried about a moth infestation, contact our nationwide network of exterminators. We’ll connect you to a pest control pro, near you, in seconds for free. Scheduling through our partner network helps support Pest Pointers and the free content we provide. Thank you tons!

When should you replace mothballs?

Naturally, suppose you’re concerned about the effectiveness of mothballs and keeping your clothes protected.

You can start to check on your mothballs after 3-6 months of them being in the container, where you may begin to start replacing them.

Ensure that you’re using heavy-duty gloves when replacing mothballs and having proper ventilation flowing in the house.

Why do mothballs dissolve?

According to the National Pesticide Information Center, mothballs that are manufactured in the United States generally contain one of the two following active ingredients:

  1. Naphthalene
  2. Paradichlorobenzene

Try saying paradichlorobenzene out loud while you’re at it. That’s a tough one.

Nonetheless, both of these chemicals are crucial to the design and effectiveness of a mothball. The purpose of mothballs IS to dissolve.

When mothballs dissolve, they emit one of either naphthalene or paradichlorobenzene (depending on what one the product was made with) into a gausses vapor that eliminates clothes moths and their larvae.

So, if mothballs didn’t begin to dissolve, they wouldn’t be omitting their gausses vapor and, thus, would be much less effective while in use.

Will a mothball dissolve sooner in hot or cold temperatures?

Ah, the age-old question.

Don’t worry; we’ve got an age-old answer.

So, can mothballs technically melt?

Mothballs will dissolve faster in warmer temperatures. Naphthalene, for instance, one of the most common active ingredients in mothballs, has a melting point of 176.5°F (80°C)

Theoretically, when mothballs reach 80°C, they will dissolve into their gausses state.

Note – I’m not a chemist by any means, but I am a person who believes he has a few shreds of common sense (hopefully.)

I would bargain that the warmer the temperature is that your mothballs are being stored in, the more likely they are to begin to dissolve and breakdown faster.

While you may have a tough time controlling the weather, make sure that if you’re storing an airtight mothball-filled container, you place the container in a well-shaded area away from windows where the sun could heat it up.

Clothes Moth Sitting on Leaf

What are some good alternatives to mothballs?

Depending on your issue, there are all sorts of alternatives to mothballs that can do quite well.

First up, you can just simply get a plain ol’ moth trap. The MothPrevention Powerful Moth Traps for Clothes Moths and comes highly regarded.

These refillable moth traps release a pheromone that attracts moths. Once the moths are attracted, they get stuck to the extremely sticky glue sheets that MothPrevention created.

If you’re a mothball lover and want to keep the same feel but avoid the chemicals, then these Cedar Wood Moth Balls from Cedar Space are a wonderful chemical-free alternative.

Instead of having the typical mothball scent, these 100% natural products have a base cedar scent.

Since they are chemical-free, you’re able to place them directly in your closet or desired area without having to store them in an airtight container, leading to a more widespread range of the scent.

If you’re looking for something more herbal and disposable, Richards Homewares Moth Away Sachets may help meet what you’re looking for.

These herbal-based alternatives to mothballs resemble the silica packets that you find in packages of food, to a point. Treating these Moth Away Sachets the same as mothballs (storing them in airtight containers) will help to keep their effectiveness to a maximum throughout their usage span.

To add, they aren’t designed to eliminate moths and their larvae, so keep that in mind.

If you’re looking to deter pantry moths in your food and storage areas, another highly regarded moth trap comes in the form of Dr. Killigan’s Premium Pantry Moth Traps with Pheromones.

Note that Dr. KIlligan’s Moth Traps WON’T be effective against clothing moths, as this traps releases pheromones that aim to attract pantry moths.

Once the pantry moths are attracted to the trap, they get stuck to the glue sheet, helping you take care of the issue.

That’s a Wrap!

Hopefully, we provided you with a bit of help regarding the proper usage of mothballs, just how and if they expire, and some friendly mothball alternatives.

As always, if you’re looking for a professional to help take care of a moth issue for you, call our nationwide network of exterminators, where we’ll connect you to a local pest control professional near you for free.

Happy moth repelling!


Pinto, G. (2005). Chemistry of moth repellents. Journal of chemical education, 82(9), 1321.

Lim, H. C. (2006). Mothballs: bringing safety issues out from the closet. Singapore medical journal, 47(11), 1003.

Kong, J. T., & Schmiesing, C. (2005). Concealed mothball abuse prior to anesthesia: mothballs, inhalants, and their management. Acta anaesthesiologica scandinavica, 49(1), 113-116.

Stone, D. L., & Stock, T. (2008). Mothballs: proper use and alternative controls for clothes moths.

Rohr, B. R., & Dorion, R. P. (2018). What’s Eating You? Clothes Moths (Tineola Species). Cutis, 101(6), 413-414.

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