Do Bath Bombs Expire? Is It Ok To Use An Old One?

Maybe you’ve happened upon a bath bomb that you vaguely remember getting as a birthday gift last year… or was it the year before? Or maybe you elected to make homemade bath bombs instead of bread, as your quarantine hobby. And now find yourself with a surplus.

Either way, right about now, you’re probably asking yourself – do bath bombs expire?

Yes, bath bombs expire. Everything that’s made with natural ingredients expires eventually, bath bombs included.

In this article, we are going to look at bath bombs, what they’re made from, how long they last, and how to know when to toss them out.

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Do Bath Bombs Expire?

Bath bombs do indeed expire. They should last for around 6 months, though if you have unusual ingredients like fresh flower petals, they will last for a shorter time.

A shelf life describes the amount of time it takes a product or ingredient to essentially stop working as it’s been advertised, or as it’s supposed to work.

The shelf life of any product is dictated by the ingredient it contains with the shortest shelf life.

Okay so that settled, let’s look at what bath bombs are made from to determine how long they’ll last.

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Bath Bomb Ingredients And Their Shelf Lives

There are three primary ingredients that make up a bath bomb.

1.   Baking Soda

Baking soda has a shelf life of about six months. Bearing in mind that the shelf life refers to the time it’s still effective having been stored in a cool and dry environment.

After six months, baking soda won’t go bad in the sense of becoming rancid or moldy. It just loses its chemical effectiveness. In other words, your bath bomb won’t be fizzy.

After six months, baking soda won’t go bad in the sense of becoming rancid or moldy. It just loses its chemical effectiveness. In other words, your bath bomb won’t be fizzy.

2.   Citric Acid

The shelf life of citric acid is approximately three years. Citric acid also does not become rancid or grow mold after its expiry date. As with baking soda, it just loses its chemical effectiveness.

Baking Soda on its own will not make your bath bomb fizz. Citric Acid, along with baking soda and the water in your tub, are all required for this chemical reaction to take place.

Citric Acid, along with baking soda and the water in your tub, are all required for this chemical reaction to take place.

3.   Cornstarch

Cornstarch has an almost indefinite shelf life, even after it’s opened (as long as you keep it stored in a cool, dry place).

The cornstarch in a bath bomb is crucial to slow down the reaction between the baking soda and citric acid. By binding to the baking soda as well as the citric acid, the cornstarch slows down the time it takes for the bath bomb to dissolve.

That makes the bath bomb fizz last several minutes, as opposed to just seconds.

So don’t go trying those 2-ingredient DIY bath bomb “hacks” that are making the rounds of social media, because you’ll be very disappointed.

So don’t go trying those 2-ingredient DIY bath bomb “hacks” that are making the rounds of social media, because you’ll be very disappointed.

Now if we are going by the logic that the shelf life of a product is dictated by the ingredient that essentially goes bad the fastest, you’re looking at about six months. This is because that’s how long it takes baking soda to expire and lose its effectiveness, thereby rendering your bath bomb a big dud.

That said, although baking soda, citric acid and cornstarch are all you need to make a bath bomb, most bath bombs contain other ingredients, like food coloring, fragrances, and essential oils. Most of those ingredients will stand up to the six-month mark as well.

However, if you’re purchasing a super specialty bath bomb that’s advertised as organic, all-natural, vegan, gluten-free, non-dairy, cruelty-free with ingredients like fresh flower petals or hazelnut oil:

1. You probably paid too much for it
2. Depending on what ‘all-natural’ ingredients are in it, may make the shelf life much shorter.

Just a side note: pretty much all bath bombs are vegan and cruelty-free.  

Just a side note: pretty much all bath bombs are vegan and cruelty-free.  

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What Happens If You Use An Expired Bath Bomb?

Nothing. Literally nothing will happen.

It’s not harmful.

But apart from maybe coloring your bath water if your bath bomb has added color, you will not get the fizz or the nice smells or basically any of the benefits you put the bomb into your bath to get.

Don’t forget, all those skin-soothing and hydrating oils in your bath bomb have an expiry date, too.

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Why Doesn’t My Bath Bomb Fizz?

If you are using an older bath bomb, it’s not fizzing because it’s expired. If you are using a bath bomb you bought less than six months ago, it’s because it was either sitting on the shelf for a very long time before you bought it, or the conditions that it was sitting in were not cool and dry.

Storing bath bombs (or displaying them for sale) in direct sunlight, warm temperatures, or in a humid environment will cause them to become ineffective a lot more quickly.

Storing bath bombs (or displaying them for sale) in direct sunlight, warm temperatures, or in a humid environment will cause them to become ineffective a lot more quickly.

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How A Bath Bomb Works: The Science

Even when you know the answer to a question, it’s always important to know why. Otherwise, instead of being a smarter person, you are just someone who knows more random trivia.

The fizziness of bath bombs comes from the chemical reaction that happens when baking soda and citric acid come into contact with water.

The fizziness of bath bombs comes from the chemical reaction that happens when baking soda and citric acid come into contact with water.

Baking soda (NaHCO3) quickly dissolves in water, and the positively charged sodium (Na+) breaks apart from the negatively charged bicarbonate (HCO3-).

While this is happening, the citric acid also dissolves, with a single hydrogen ion (H+) separating from the rest of the molecule.

The positively charged hydrogen from the citric acid and the negatively charged bicarbonate from the baking soda come together to produce an immediate series of reactions. One of these reactions is the production of carbon dioxide, which is what forms the little bubbles, i.e. the fizzing action.

Now as we mentioned before, the cornstarch is there to slow down the reaction, without which, your bath bomb would have fizzled out within just a few seconds.

The carbon dioxide that is produced is not only for creating the fizz, but if your bath bomb has scented oils, those are also released into the air as the carbon dioxide bubbles break the surface of the water.

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Take Away

Do Bath bombs expire? Yes, they do.

Assuming your bath bomb hasn’t been stored on a window sill in direct sunlight, or stored in the one tiny bathroom that you share with your three other roommates who love long hot showers, most bath bombs last about six months before they start losing their fizz and other benefits.

While using an expired bath bomb is not going to have any real negative effects, other than disappointment, it’s maybe time to ditch the old, expired bath bomb for a new one.

We’ve put together a list of bath bombs that are out there waiting for you to try them. And instead of highlighting the “trending” bath bombs that are going for $10-over $20 each for something you can literally make at home in your own kitchen, we’re going the more budget-friendly route.

Because at the end of the day, who has time to make bath bombs? And on what planet does it make sense to flush $20 on a bath, down the drain?

Dr. Teal's 5-Count Ultra Moisturizing Lavender Bath Bombs 

Made with jojoba, almond, and sunflower oil and the scent of lavender, Dr. Teal’s Ultra Moisturizing Lavender Bath Bombs give you the triple whammy of hydrated skin, a dose of calming aromatherapy, and being super budget-friendly.

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No products found.

Envelop yourself with the relaxing scent of lavender and chamomile to calm and comfort the body and mind, while its patented moisture renew blend leaves your skin feeling soft and smooth. These bath bombs are gentle enough for sensitive skin.

 LifeAround2Angels Bath Bombs Gift Set 

Made with shea and coco butter (great for Does Shea Butter Help With Stretch Marks? for smooth, moisturized skin, the LifeAround2Angels Bath Bomb gift set are among the most cost-effective bath bombs out there. And we love that the nice colors won’t stain your tub.

Laguna Moon Soothing, Calming Bath Bombs 

Actually marketed for children and babies to ensure a restful night’s sleep, these soothing bath bombs with lavender and tea tree oil will calm and relax anyone regardless of their age. And because they are safe for babies, you know they will be gentle on the most sensitive skin.

 Aofmee Bath Bombs Gift Set 

The Afomee Bath bombs Gift Set not only makes our top picks for being budget-friendly, but also great for kids, or adding a little something unexpected to a housewarming, bridal shower or get-well-soon gift basket.

Their fun shapes will surely put a smile on the recipient’s face. Along with skin-hydrating ingredients, they have great fragrances, like French Vanilla, Sweet Orange, and Strawberry.