♨️ Hot water bottle

A hot water bottle filled with liquid will be treated as a liquid container at the security checkpoint. If it contains more than 100ml of water — which it almost certainly does — screeners will not allow it through in carry-on and will ask you to empty it or check your bag. An empty rubber bottle passes through with no issues.

The rule is consistent globally: the bottle itself is always permitted, and the only restriction applies if it contains liquid. The 100ml liquid rule used in the US, UK, EU, Canada, and Australia all treat a liquid-filled hot water bottle the same way. No country's aviation authority has a special carve-out or stricter rule specifically for hot water bottles.

Some airport lounges and cafes will provide hot water on request, but most standard airport outlets will not fill a hot water bottle as a routine service. Your best option is to bring it empty through security and fill it at your destination — hotel kettles work perfectly for this. Alternatively, you can ask a flight attendant to fill it with hot water once you are on board, though not all airlines will accommodate this.

Pack it empty and deflate or flatten it as much as possible before placing it in your carry-on. Its rubber material can look unusual on an X-ray, so keeping it near the top of your bag makes it easy to pull out if a screener wants a closer look. If you are checking bags, the bottle can go in either — there are no restrictions on the empty bottle in checked baggage.