Why you can't take this item in your hand luggage when travelling to the US

You've booked your flights in the British Airways mega sale, you're checking in to one of the most Instagrammable Airbnbs and you've packed all your summer dresses and sandals.

But if you're heading to the US, there's one thing you need to be sure isn't in your hand luggage.

Currently passengers aren't allowed to carry liquids over 100ml in the bag they bring onboard. However, if you're heading to the US you're also only permitted to take a limited amount of powder. The TSA explains that powder products (think milk powders and powder cosmetics) are restricted to 350ml (or 120z).

The rules are: 'If you are travelling from an international last-point-of-departure to the US, powder-based substances in carry-on baggage greater than 350ml or 12 ounces may require additional screening at the central checkpoint.

'Powder-like substances over 12 oz. or 350ml in carry-on that cannot be resolved at the central checkpoint will not be allowed onto the cabin of the aircraft and will be disposed of.

'For your convenience, place powders in your checked bag. The measures have already been implemented at US airports nationwide to identify and prevent potentially dangerous items from being brought aboard the aircraft. There are no changes to what is allowed in carry-on baggage at US airport checkpoints.'

The UK Foreign and Commonwealth Office says: 'Food items and powders in your hand luggage can obstruct images on x-ray machines.Your bags may need to be checked again manually by security. You can put these items in your hold luggage to minimise delays.'

So now you know.