Sterilising baby bottles is an important part of bottle feeding to help reduce the risk of illness from germs and bacteria. However, sterility does not last forever, so it’s important to know how long bottles remain sterile after sterilising.
Quick Answer
Most experts agree that baby bottles will remain sterile for 24 hours after being sterilised as long as they remain untouched and sealed in the steriliser. However, it’s best to use bottles within 6 hours of removing them from the steriliser. Any bottles not used within 6 hours should be re-sterilised.
How Sterilisation Works
Sterilising baby bottles kills 99.9% of germs, bacteria, viruses, fungi and spores that can make a baby sick. There are several ways to sterilise bottles including:
- Steam sterilising using a dedicated steam steriliser
- Boiling in a large pot of water for 10 minutes
- Using a microwave steam steriliser bag
- Cold water sterilising by fully submerging bottle parts in sterilising solution for at least 15 minutes
Any of these methods are effective when done properly. However, it’s important to note that sterilisation does not provide indefinite protection. Over time, airborne germs can settle back onto the sterilised surface of bottles and parts. Moisture allows bacteria to grow. And handling items with unclean hands introduces new germs.
How Long Bottles Stay Sterile in the Steriliser
Bottles and parts will remain sterile after sterilisation as long as they remain completely sealed inside a closed steriliser away from air, moisture and handling. In an unopened steam steriliser or covered sterilising solution, bottles can remain sterile for up to 24 hours provided the lid remains tightly closed.
In Steam Steriliser
In a steam steriliser, bottles will stay sterile for 24 hours if the steriliser remains closed with the lid on tight. This keeps out airborne germs and moisture. Opening the lid allows contaminants in, so keeping it closed maintains sterility.
In Sterilising Liquid
Submerged in sterilising liquid inside a closed container, bottles will also stay sterile for 24 hours. The liquid acts as a barrier preventing airborne germs from settling. As long as bottles remain fully submerged with the lid tightly on the container, they will remain sterile.
How Long Bottles Stay Sterile After Removing From Steriliser
Once bottles are removed from the steriliser and exposed to open air, the sterility period begins to decline. Most experts agree sterility is only maintained for up to 6 hours after removing bottles from the steriliser provided they remain untouched.
0-6 Hours After Removal
For the first 0-6 hours after removing bottles from the steriliser, it is generally safe to assume they remain sterile provided they have not been touched or handled in any way. Avoiding contact preserves sterility.
6-24 Hours After Removal
From 6-24 hours after removing bottles from the steriliser, sterility begins to decrease. Airborne germs can settle back onto surfaces. Any handling or touching introduces new germs. Bottles may remain relatively sterile, but risks increase over time.
Beyond 24 Hours After Removal
After 24 hours outside of the steriliser, bottles should not be assumed sterile. The longer bottles sit out exposed, more and more germs settle and grow on surfaces. Beyond 24 hours, it is safest to re-sterilise before using bottles again.
How to Preserve Sterility
To help baby bottles retain sterility for as long as possible after removing from the steriliser:
- Avoid touching inside surfaces
- Keep bottles capped and assembled
- Store upside down to avoid dust inside
- Cover with clean dishtowel or paper towel
- Keep in clean cupboard or drawer away from dirt
- Only handle clean hands
When to Re-Sterilise Bottles
To ensure safety, bottles should be re-sterilised:
- After 24 hours outside of the steriliser
- Before first use straight out of package
- After being used
- After being dropped or coming into contact with unclean surface
- If bottles appear dirty or contaminated in any way
It’s better to take a few extra minutes to re-sterilise when in doubt than risk harming baby with germs.
Signs Bottles May No Longer be Sterile
Watch for these signs that bottles may need re-sterilising:
- More than 24 hours after sterilising
- Appear dusty or dirty
- Touched with unwashed hands
- Stored open or upside down
- appear wet or have moisture inside
- Left out of fridge for more than 1 hour
When in doubt, it’s best to re-sterilise.
Storing Sterilised Bottles
To prolong sterility of bottles after sterilising:
- Store assembled with cap, ring, lid, etc. firmly in place
- Keep upside down in clean, enclosed container
- Use within 24 hours for best results
- Okay to store in fridge or cool, dry place
- Avoid extreme hot or cold temperatures
- Do not freeze sterilised bottles
Proper storage extends the sterile period.
Preparing Sterilised Bottles for Use
When ready to use a sterilised bottle:
- Wash hands thoroughly before handling
- Inspect bottle interior – should be dry with no moisture or dust
- Clean feeding surface/table
- Use clean spoon/scoop to handle formula or breastmilk
- Do not touch inside of bottle
- Assemble carefully to avoid contamination
Careful handling maintains sterility when preparing to use.
How Many Times Can You Reuse a Sterilised Bottle?
With proper handling between uses, a sterilised bottle may be reused multiple times before needing to re-sterilise, such as:
- 2-3 uses if handled with care
- Up to 24 hours unrefrigerated if kept totally sterile
- Up to 1 hour out of fridge between uses if capped
However, at any sign of contamination, dirt or milk left behind – re-sterilise.
Reusing Bottles After Refrigerating Between Uses
Bottles can be reused by refrigerating leftover milk between feedings, provided:
- Only keep refrigerated 1 hour or less
- Cap tightly between uses
- Store towards back of fridge not door
- Discard after 1 hour out of fridge
- Wash thoroughly before reusing
Bottles kept refrigerated between uses should not be stored longer than 1 hour at room temperature.
Microwaving Versus Re-Sterilising Bottles
Some parents microwave used bottles to reheat them instead of fully re-sterilising. However, microwaving has risks:
- May not kill all germs or bacteria
- Can create hot spots and burn baby
- Can warp or damage plastic
- May leave behind milk film
For safety, it’s better to fully re-sterilise bottles between each use.
Sterilising Breast Pump Parts
Like bottles, breast pump parts should be sterilised regularly for safety:
- Pump parts should be sterilised daily
- Can reuse if refrigerated between pumps
- Store in fridge no more than 24 hours
- Wash thoroughly in hot soapy water between uses
- Air dry fully before sterilising
Properly sterilising pump parts reduces bacteria intake for mom and baby.
Using a Microwave to Sterilise
Microwave steam bags offer a convenient sterilising option. However, take care to:
- Use only microwave-safe sterilising bags
- Follow microwave manufacturer recommendations
- Lay bag flat and vent any air
- Microwave only with water – no bottles inside
- Rotate bag during cycle
- Ensure even steaming throughout
Microwave sterilising can damage parts if not done properly. Follow all instructions carefully.
Sterilising With Boiling Water
Boiling bottle parts in water can also sterilise. Take care to:
- Use deep pot with lid to prevent burning
- Completely submerge all bottle parts
- Boil vigorously for full 10 minutes
- Turn off heat before removing
- Use tongs to avoid burns
Boiling parts for the full recommended time ensures proper sterilisation.
How Long Do Sterilising Tablets Last After Opening?
Once opened, sterilising tablets remain effective for:
- 6 months – Powdered tablets
- 3 months – Liquid concentrate
Mark opened packages with date opened. Discard expired tablets that are past useful life.
How to Sterilise Bottles Without Any Products
If no commercial sterilising products are available, try these methods:
- Dishwasher – run on hot cycle with heated drying
- Steam – steam for 5 minutes in covered pot
- Oven – 30 minutes at 140F/60C
- Vinegar – submerge in 1 part vinegar to 3 parts water for 1 hour
- Bleach – make 1 tablespoon bleach per 1 litre water solution
- Hydrogen Peroxide – 3% solution, soak 10 minutes
With some household items, effective diy sterilising is possible in a pinch.
Sterilising FAQs
How do you keep bottles sterile between uses?
Keep bottles sterile between uses by capping tightly, refrigerating if stored with milk or formula, using clean spoon to handle contents, washing hands before touching, and avoiding storage longer than 1 hour unrefrigerated or 24 hours refrigerated.
Do sterilised bottles need washing?
Yes, used bottles should always be washed thoroughly with soap and hot water first before sterilising, even if they contained only sterilised breastmilk or formula.
Is it safe to use expired sterilising solution?
No, expired sterilising solution should not be used as it may no longer be potent enough to fully kill germs and bacteria.
Do you have to sterilise bottles for every use?
It is ideal to sterilise bottles before each use. However, with careful handling, cleaned bottles can be safely reused for up to 24 hours unrefrigerated or 1 hour refrigerated before needing to re-sterilise.
Can you sterilise too much?
There’s no need to sterilise more than you need. Sterilising too many bottles or too often won’t provide any extra protection. Focus instead on proper hygiene practices between sterilisations.
Is warm soapy water enough to clean bottles?
Warm soapy water is fine for cleaning bottles after use, but does not sterilise them. Bottles should be sterilised by steam, boiling or chemical methods for full protection.
Do you have to sterilise bottles for breastmilk?
Yes, it is recommended to sterilise bottles even if they will be used for breastmilk. Sterilising kills germs that can come from improper handling and storage.
Conclusion
To summarise, most experts agree that sterilised bottles will remain sterile for:
- 24 hours sealed inside closed steriliser
- 6 hours after removing from steriliser if untouched
- Less than 24 hours outside of steriliser
Bottles should be re-sterilised every 24 hours at a minimum, or sooner if mishandled or contaminated in any way. Proper handling and storage extends sterility. But when in doubt, take a few extra minutes to re-sterilise bottles for safety.
