There is a particular kind of defeat in watching a security officer tip an almost-full bottle of face wash into a bin at half five in the morning. You knew the rule. You meant to decant. You ran out of time.
The rules themselves are not complicated; the packing is what catches people out. What follows is the version of the checklist that survives a real airport morning — what counts as a liquid, what actually fits in the bag, and how to decant well enough that nothing leaks into your socks.
What Counts as a Liquid at UK Security
Most of us picture water, shampoo and sun cream. Security staff work to a wider definition: anything you can pour, spread, spray, pump, squeeze or smear. If it holds its shape in a jar and you scoop it out with a finger, treat it as a liquid.
That catches out more people than you would expect. Toothpaste, roll-on deodorant, mascara, lip gloss, liquid foundation, concealer, hand sanitiser, hair gel, shaving foam, contact lens solution, perfume and aftershave all count. So do honey, jam and peanut butter, which have ended many a lovingly made sandwich.
The ones that surprise people are usually the ones nobody thinks of as wet. Aerosol deodorant, dry shampoo in a can, hairspray, mousse, nail varnish and nail varnish remover, micellar water, toner, serum, eye drops, mouthwash, saline, beard oil and cuticle oil are all liquids for the purposes of the tray. Soft cheese, pâté and dip are liquids. A snow globe is a liquid, and a genuinely heartbreaking number of them end their journey in a bin at Gatwick.
Lip balm is the classic grey area. In a squeezy tube it is a liquid; in a flat tin it is generally treated as a solid, but the safest move is to buy it in a tin and not argue the point at 6am.
If you can pour it, spray it, pump it, squeeze it or smear it, it is a liquid. Everything else is a judgement call you would rather not have at the belt.
The 100ml Rule, Properly Explained
The rule is about the container, not the contents. A 200ml bottle with a teaspoon of moisturiser left in it is still a 200ml bottle, and it still goes in the bin. This is the single most common and most maddening misunderstanding at the tray table, and it has cost more expensive skincare than any other line in the rulebook.
The rest of the rule, in plain terms:
- 100ml or less per container — as printed on the bottle, not as estimated by eye.
- One clear resealable bag, roughly 20cm by 20cm — the size of a one-litre freezer bag, and no bigger.
- One bag per passenger. Not one per family, not one per handbag, not one for you and one for your partner's contact lens solution.
- The bag must be sealed and must come out of your luggage at the scanner. Opaque wash bags, knotted carrier bags and hotel laundry bags do not count, however neatly packed.
A note on the new scanners: several UK airports have installed CT equipment that allows larger containers, and the rules have shifted back and forth as the rollout has been delayed. Check your specific airport's website in the week before you fly rather than relying on what a friend told you last summer. Packing to the 100ml rule is never wrong. Packing to the newer rule at an airport still using the old one is an expensive mistake.
The Kit That Actually Fits
A one-litre bag sounds generous until you start filling it. Here is what tends to make the cut on a trip of a week or so, in roughly the order you would squeeze them in:
- 50ml shampoo, or a shampoo bar
- 50ml conditioner
- 30ml body wash, or none at all if you are staying in a hotel
- 50ml sunscreen, plus a 100ml if you are going somewhere hot
- 30ml cleanser and 30ml moisturiser
- A 50ml travel tube of toothpaste, not the family one
- Roll-on or solid deodorant
- 30ml perfume or aftershave
- Contact lens solution, if you wear lenses
That is nine containers before you have packed a single item of makeup. The lesson is not to find smaller bottles; it is to pack fewer things. Hotels, Airbnbs and friends' bathrooms will cover shampoo, conditioner and body wash. Take the things you are genuinely fussy about and buy the rest when you land.
Decanting without the mess
A few habits make the difference between a bag that survives the flight and a bag that has to be thrown away at the far end:
- Fill to about three-quarters. Liquids expand with cabin pressure, and a bottle filled to the brim will find the seal.
- Use bottles with a proper screw cap, not a flip-top. Squeeze the air out before sealing — air is what pushes the liquid out.
- Seal the clear bag inside a second, cheap freezer bag. It costs nothing and it contains the one leak that gets through.
- Tape the lids with a strip of electrical tape, or put a square of cling film under the cap, if you are carrying something precious.
- Label every bottle with a marker. At 6am, 30ml of white cream could be cleanser, conditioner or hand cream, and you will not remember.
What You Can Take Out of the 100ml Rule
A few categories are exempt, and knowing them saves you throwing away things you did not need to.
- Prescription medicines in liquid form, in the quantity needed for the trip. Bring the prescription or a copy of it.
- Baby food, baby milk and sterilised water in the amount needed for the journey. You may be asked to taste it.
- Breast milk, including in bottles and cool bags.
- Essential liquid dietary requirements, such as certain medical nutrition products.
These do not go in the clear bag. They need to be declared and handed to the security officer separately, so keep them in a pouch at the top of your hand luggage rather than excavating your entire rucksack at the belt.
The Night-Before Routine
People rarely lose their toiletries through ignorance. They lose them to the 4am scramble. Twenty minutes the night before is the whole game:
- Lay everything out, then put back anything that is not essential.
- Decant, filling to three-quarters and wiping the threads clean before capping.
- Seal the clear bag, then seal it inside a second bag.
- Put the whole thing at the top of your hand luggage — not at the bottom, and never in the bag going into the hold.
- Screenshot your airport's security page, in case the rules have moved again.
If It Goes Wrong at Security
You still have options, and they are not all bad.
- Many airports offer a paid courier or "post it home" service. Expensive, but better than losing a full bottle of something you love.
- Some security areas will hold items briefly if you can return for them. Ask — but do not build a plan around it.
- Buy it airside. Anything you buy past security is exempt from the liquid rule at the point of purchase, provided it is sealed in a tamper-evident bag with the receipt, and you do not open it before your final destination.
- Solid toiletries solve the problem entirely. Shampoo bars, solid conditioner, bar soap, solid deodorant, toothpaste tablets, powdered cleanser and solid perfume are not liquids. They are not counted, and they cannot leak into your socks.
The best carry-on toiletry kit is not the one with the cleverest bottles. It is the one you pack on a Tuesday for a Saturday flight, and then entirely stop thinking about.
Pack to the 100ml rule, use the clear bag properly, keep the exemptions separate and the whole thing at the top of your bag. Then the only thing to worry about at half five in the morning is the flight.
Photo: JoshuaWoroniecki / Pixabay
