In the UK, baby milk and baby food are exempt from the standard "100ml liquid rule," meaning you are allowed to carry enough for your journey in your hand luggage. There is no specific legal limit (like a liter or gallon), but the amount must be "reasonable" for the length of the flight and any potential delays. This exemption applies to breast milk, sterilized water, and formula milk, provided the baby is traveling with you. If you are traveling without a baby, you can still carry up to 2,000ml (2 liters) of expressed breast milk in individual containers in your hand luggage, but this must not be frozen. At the security checkpoint, be prepared for officers to screen the liquids separately; they may need to open the containers or ask you to taste the liquid to verify its authenticity. Most UK airports, like Heathrow and Gatwick, also offer a "reserve and collect" service where you can pre-order ready-to-drink formula to pick up after you pass through security.