Do Bath Bombs Expire? How Long Do They Last and How to Tell

Do Bath Bombs Expire?

The simple, short answer is yes, bath bombs do expire. Most bath bombs are at their best within six months of being made. Don't get me wrong, after this time they're certainly still safe to use, but you may notice they don’t fizz as strongly. Moving further past the 6 month mark, you may also notice their fragrance is weaker, or their colours start looking a little faded.

The true tell of how long a bath bombs shelf life will be depends most heavily on the oils used in its recipe. Some oils are naturally long-lasting and stable, such as coconut oil ( which I personally adore using! ), remaining stable for over two years when stored properly. On the other hand, oils like grapeseed have a much shorter shelf life, often around six months to a year. This difference in oil stability is one of the biggest factors that determines a bath bombs shelf life.

Outside of oils, it's also important to remember that the bulk of bath bomb ingredients are reactive, and over time they naturally lose their potency - which brings us to our next point:

Why Bath Bombs Expire

Bath bombs are typically made from baking soda and citric acid, with optional additions like oils, scents, and colourants. These ingredients can either oxidise or activate when exposed to air, moisture, or light.

Citric acid and baking soda are responsible for the fizzing reaction, but they become less effective the longer they sit around due to moisture - the most common culprit being humidity.

Essential oils and certain fragrances on the other hand, are made up of volatile aromatic compounds that slowly evaporate and naturally lose their scent over time. Depending on storage conditions, when exposed to too much light and/or heat they can also go rancid and develop an odd, and often times quite unpleasant, smell.

(Side tangent)

When an oil goes rancid, it means the chemical compounds inside have oxidised or broken down. This process doesn't just change the fragrance, it can create by-products that are irritating to the skin and respiratory system. Rancid oils often contain peroxides and aldehydes, which are unstable and may cause redness, itching, or allergic-type reactions when used in cosmetics or bath products.

Colourants can also fade or discolour with time (one of the biggest culprits of discolouration isn't even a colour!). Thankfully, this doesn't mean the bath bomb is now harmful, it simply means it might not look as vibrant as the day it was made. The fizz, fragrance, and overall bathing experience are usually still perfectly fine.

Signs a Bath Bomb is Too Old

If you're not sure whether your bath bomb is past its prime, thankfully there are a few things you can check. A crumbly or cracked texture is a common sign of age, it's a very typical sign of moisture damage and is a telltale indicator of very weak fizz. The opposite can also be true - when a bathbomb seems abnormally hard, and almost seems to 'clink' when you hit it, the bath bomb is also unlikely to fizz anymore.

Another way to tell is by the scent. If the fragrance has simply faded, that's usually not a problem - it just means the bath bomb has lost some of its strength. However, if the smell has turned odd or unpleasant, it may indicate the oils inside have gone rancid. In very rare cases, when a bath bomb is stored in a damp, warm environment, it can even develop mould. If that happens, the safest choice is to dispose of it rather than use it.

How to Store Bath Bombs So They Last Longer

A good approach to storage can help bath bombs last closer to that full year mark. The best way to preserve their fizz and fragrance is to keep them in an airtight container or sealed jar, away from humidity. A cool, dry place away from sunlight is ideal, so avoid leaving them in the bathroom where steam is common. Wrapping them in foil or cling wrap also adds extra protection by keeping moisture out. Personally, I prefer wrapping bath bombs in shrink film for this very reason.

Can You Still Use Expired Bath Bombs?

'Expired' bath bombs are generally safe to use, but the experience won't be much to write home about. You'll still get a soak, but you'll likely miss out on the iconic fizz fragrance that comes with a fresh bomb. If your bath bomb looks fine and smells normal, it's usually okay to use, even after the twelve month mark. The only time you should avoid it is if it shows visible mould, or has an unpleasant smell.

Final Thoughts

Bath bombs don't last forever, but they also don't go 'bad' in the same way food does. The main change is a loss of visual and olfactory effectiveness rather than safety. For the best experience, use your bath bombs within six months, and store them properly to keep them fresh.