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Sterilising Baby Bottles

Sterilising Baby Bottles
During their first year of life, babies are most vulnerable to infection because their immune systems are not fully developed.

If bottles are not sterilised they provide a perfect environment for viruses, bacteria and parasites to grow. These bugs can cause your baby to become ill, so it is very important to sterilise all of your baby's feeding equipment until they are at least one year old. By this point they will have started to produce their own antibodies against disease so they are more resistant to infection.

All parts of the bottle (including teats, retaining rings, caps and lids) must be sterilised before each feed.

The first thing to do is to clean each part using hot, soapy water and a bottle brush. Make sure all milk is removed from the bottle (this is easier to do straight after a feed, before the milk has had a chance to dry). Milk curds can survive the sterilising process so it is important to ensure absoutely all of the milk is washed out. If your bottles are dishwasher friendly you can wash them in the dishwasher, although it is advised that you wash the teats separately by hand so you can remove stubborn milk curds that the dishwasher might miss. Rinse off soap suds with clean water.

While cleaning the equipment you should check that there are no scratches or cracks anywhere because germs can squeeze into these crevices and hide away from the cleaning and sterilising processes. If any of your bottles are damaged, get rid of them.

Once all milk has been removed, the bottles are ready to be sterilised. This can be done in a number of ways:

Electric Steam Sterilising

Steam sterilisers vary slightly so make sure you follow the instructions provided with your particular machine. Check that your equipment is safe to steam before using a steam steriliser. Bottles and teats should have their openings face down so they can be properly sterilised. It usually takes around 10 minutes for the sterilising process but remember to allow time for the bottles to cool. If you leave the bottles in the machine with the lid down, they will remain sterile for about six hours. If you remove the bottles before they are needed they should be stored fully assembled in a clean place to prevent the inside of the bottle becoming contaminated again (this is applicable no matter which method of sterilisation you use).

Microwave Steam Sterilising

You can buy steam sterilisers to put in the microwave (but remember, you can't put anything metal in them). Depending on the model of the steriliser and that of your microwave, the sterilising process will take between three and eight minutes (plus cooling time). If you leave the bottles inside with the lid closed, they will remain sterile for about three hours.

If you don't have a microwavable steam steriliser, you can just put the bottles, unsealed, in the microwave for 90 seconds to sterilise them.

Cold Water Sterilising

You can buy non-toxic sterilising solutions or tablets that you add to water (check the manufacturer's guide for quantities). You can either purchase containers specifically for this purpose or you can use a clean bucket or container. Make sure all equipment is fully submerged in the water and there are no air bubbles. Leave the bottles in the solution for at least half an hour. Take out the bottles when you need them but don't leave them in the same solution for more than 24 hours - at this point the water should be re-newed. When you take the bottles out you can rinse them with clean water, but it is safe to feed your baby with bottles taken straight from the sterilising solution without being rinsed.


Not all bottles are suitable for this method of sterilisation so check first. Fill a large pan with water and submerge the bottles and teats in the water making sure there are no air bubbles. Put a lid on the pan and boil for 10 minutes. Leave the lid on and remove the bottles as needed taking care not to scald yourself. Teats tend to become damaged more quickly when using this method of sterilisation so check them regularly for cracks and tears.

Dishwasher Sterilising

Baby bottles can be sterilised in a dishwasher at 80 degrees celcius. However, bacteria can begin to grow in bottles as soon as they are removed from the dishwasher so it is best to fill them straight away with formula.

To keep the bottles sterilised when preparing to feed, make sure all surfaces and your hands are completely clean. If bottles are left standing for too long they will become unsterile which is why you should leave sterilised bottles in their containers with the lids on until they need to be used. If a bottle has been out for too long you should sterilise it again before using it to feed your baby.

August 2012

The World Health Organization (WHO) strongly recommends exclusive breastfeeding for the first six months of life and states that babies fed exclusively on breast milk for their first six months will develop most healthily.

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