Sterilising Equipment

Your baby's immune system is less resistant to nasty bugs than yours, therefore you must sterilise all milk feeding equipment. This applies whether you are bottle feeding powdered infant formula milk, ready-to-feed liquid formula or expressed breast milk. Sterilisation kill germs and helps prevent stomach upsets, diarrhoea and serious infection.

You must continue to sterilise bottle feeding equipment until your baby is one year old, by which time his immune system will be mature enough to cope with potentially harmful germs. If you are weaning your baby early, his bowls and spoons used for solids should also be sterilised until he is six months old.

Preparing to sterilise

Before sterilising, you must scrub bottles, teats, breast pump parts and other feeding equipment with a bottle brush in hot soapy water, then rinse well with cold water. It is vital you get rid of traces of old milk from the insides of bottles, which are a breeding ground for bacteria.

You can also put feeding equipment in the dishwasher, but it must still be sterilised afterwards. Make sure work surfaces used for sterilising and assembling sterilised feeding equipment are clean and disinfected, and wash your hands thoroughly.

Here is an overview of the sterilisation methods you can choose from.

Electric steriliser

Possibly the most expensive option, an electric steriliser sits on your worktop and uses natural steam sterilisation to sterilise bottles and other feeding equipment. Steam sterilisation involves no chemicals and is a highly effective method of killing bacteria. An electric steriliser is easy to use – simply add water and switch it on, but it will require regular descaling to remove lime scale build-up, especially in hard water areas.

An electric steriliser takes around eight to 12 minutes to complete the sterilisation cycle, but it can keep bottles sterile for 24 hours as long as the lid remains closed (refer to the manufacturer's guidelines). Therefore you can switch it on at any time of day or night and return later to get a bottle.

Microwave steriliser

A microwave steriliser also works by turning water to steam. After adding water, it takes around 5 minutes to sterilise bottles, and stays sterile for up to 24 hours with the lid unopened (again check manufacturer's guidelines). When you take the lid off, you can use it as a clean surface for preparing feeds. There is no descaling involved – keep the unit clean by washing it in the sink or dishwasher.

With its dish-shaped design, a microwave steriliser sits conveniently inside your microwave when not in use so it doesn't take up space on your worktop. Light and portable with no power cable to worry about, you may find it more suitable for travelling than an electric steriliser. If you have no microwave available when you are away, you can simply fill the unit with cold water sterilising solution and put your bottles in that.

You can also buy steam sterilisation bags for use in the microwave. They work the same way as a microwave dish steam steriliser, they just don't hold as much stuff. Sterilisation bags are lightweight and take up little space, so they may be a good choice if you don't need to sterilise very often, or for sterilising when you are away from home.

Cold water sterilisation

Cold water sterilising may appear old fashioned in the light of modern technology, but it is just as effective as steam sterilisation and certainly has its advantages. You simply fill a bucket with water and Milton (or other sterilising solution), add your bottles, and wait for 15 minutes. Plastic toys, dummies, teething rings and other accessories can also be sterilised in this way. (You can buy a specially designed bucket with a lid that ensures equipment stays fully submerged.)

The solution stays sterile for 24 hours, during which time you can add and remove things as and when you need to. This is a bonus because you can just get out a single item and the other things inside will remain sterile. Just be aware of when you need to change the solution. There is no need to rinse items when you take them out.

Cold water steriliser has the added advantage of being easily portable because it requires no power source or microwave. An electric or microwave steriliser will be of no use to you in the event of a power cut, so it won't hurt to keep some Milton tablets in the cupboard!


You can sterilise bottles, teats and other feeding equipment by boiling them in a large pan of water. Firstly make sure items are safe to boil, then submerge them in the water completely below the surface and boil them for at least 10 minutes, with the lid on. It is best to keep the lid on and remove bottles just before you need them.

Regularly check teats for damage if you boil them – they will deteriorate faster and need replacing more often with this method of sterilisation.

How long do bottles stay sterile out of the steriliser?

This is an obvious question with seemingly no straight answer. As soon as the lid of an electric or microwave steriliser is opened, technically the contents are no longer sterile. So what are you supposed to do, sterilise a fresh bottle before each feed? This seems ludicrous if your steriliser holds several bottles at once. Your steriliser's manufacturer may be able to advise you.

The UK Department of Health advises that if sterilised bottles are not used immediately, they should be fully assembled with their teats and lids to prevent contamination. Some parents report quickly grabbing what they need out of the steriliser and putting the lid straight back on, without touching the other sterilised items.

According to the World Health Organization's guidelines for the safe preparation, storage and handling of powdered infant formula:

"To prevent recontamination, it is best to remove feeding and preparation equipment just before it is required for use. If equipment is removed from the sterilizer and not used immediately, it should be covered and stored in a clean place. Feeding bottles can be fully assembled to prevent the inside of the sterilized bottle and the inside and outside of the teat from becoming contaminated."

Other notes about sterilising