Sterilising Bottles and Equipment

Cleaning and sterilising are two separate jobs

The most common mistake is treating these as one step. They are not. Cleaning removes milk residue; sterilising kills what is left. Skipping the first makes the second much less effective, because milk film shields bacteria.

The NHS sequence is: clean bottles, teats and other feeding equipment in hot soapy water as soon as possible after a feed, using a bottle brush kept only for bottles and a small teat brush for the inside of teats. Teats can also be turned inside out and washed by hand. Never use salt to clean teats; the NHS calls this dangerous for your baby. Rinse everything in clean cold running water before sterilising.

A dishwasher counts as cleaning, not sterilising. The NHS is explicit: "putting feeding equipment through the dishwasher will clean it but it does not sterilise it". Load bottles, lids and teats facing downwards, and consider washing teats separately by hand so you can be sure they are properly clean.

The three methods and their timings

Cold water sterilising solution

Follow the manufacturer's instructions, leave equipment in the solution for at least 30 minutes, and change the solution every 24 hours. Make sure no air bubbles are trapped inside bottles or teats, because an air pocket is an unsterilised pocket. Your steriliser should have a floating cover or a plunger to keep everything under the surface.

If you use this method, remember the follow-on rule from formula preparation: shake off excess solution or rinse with cooled boiled water from the kettle, not with tap water.

Steam sterilising

Electric and microwave steam sterilisers vary enough that the NHS simply says to follow the manufacturer's instructions. The HSE rates steam as the best of the available methods, with plug-in and microwavable options both acceptable.

Boiling

Check first that the items are safe to boil. Boil them in a large pan for at least 10 minutes, keeping everything under the surface, and set a timer so you do not forget to turn the heat off. Teats degrade faster with this method, so check regularly that teats and bottles are not torn, cracked or damaged. A split teat is both a hygiene problem and a choking risk.

What the HSE advises against

Ireland's HSE specifically says not to use UV sterilisers, which work by ultraviolet-C radiation, on the grounds that there is not enough research to show they are safe and effective for this purpose. That is a live divergence from the UK, where UV devices are sold without a national position against them.

After sterilising, which is where it usually goes wrong

Sterile equipment stops being sterile the moment it is handled carelessly. The NHS advice is to leave bottles and teats in the steriliser or pan until you need them. If you do take them out, put the teats and lids on the bottles straight away. Wash and dry your hands before handling sterilised equipment, or better, use sterile tongs. Assemble bottles on a clean, disinfected surface or on the upturned lid of the steriliser.

How long to keep going, by country

This is where the guidance separates sharply.

The UK. The NHS says to sterilise all your baby's feeding equipment, including bottles and teats, "until they're at least 12 months old", and repeats the twelve-month figure in its bottle feeding advice. The stated reason is protection against infection, particularly diarrhoea and vomiting. The same advice applies whether the bottle holds expressed breast milk or formula.

The United States. The AAP's page on the subject opens by acknowledging that "parents and pediatricians today are not as concerned with sterilizing bottles and water as they were a generation ago". It considers a dishwasher with heated water and a hot drying cycle, or thorough washing in hot soapy water with a good rinse, sufficient to kill most germs on glass bottles, and mentions that some experts recommend boiling teats for five minutes. The CDC's formula preparation guidance simply states that bottles need to be clean and sanitised.

If you are following NHS or HSE advice, sterilise for the first year. If you are in the US, the bar is lower for a healthy full-term baby, and higher for one who is very young, was born preterm, or is immunocompromised.

What you actually need to buy

The NHS's list is short: several bottles, teats, a bottle brush, and sterilising equipment, which can be a cold-water steriliser, a microwave steriliser or a steam steriliser. On the endless question of which brand of bottle or teat is best, the NHS position is that "there's no evidence that 1 type of teat or bottle is better than any other", and that simple bottles which are easy to wash and sterilise are probably best. The HSE suggests having at least six bottles, lids, discs and teats so you are never sterilising under time pressure, and recommends wide-necked bottles if you have a visual impairment, because they are easier to fill.

Teat flow and when to replace things

Teats are consumables. Replace one that is torn, cracked, discoloured or sticky. If the hole has widened, milk flows too fast; the NHS notes that drinking milk too quickly can make a baby sick, and suggests checking that the hole in the teat is not too big if your baby is often bringing up milk. If a teat gets blocked mid-feed, swap it for another sterile teat rather than trying to clear it. If a teat goes flat because the bottle has developed a vacuum, release the suction by pulling gently on the corner of your baby's mouth.

What this does not protect against

Sterilising equipment does nothing about the powder. Powdered formula is not sterile in the tin, which is why the water temperature rules exist separately. Perfect sterilising plus cool water is not a safe combination under UK guidance. The two steps solve different problems and you need both.