Most of us know the 3.4-ounce rule. You empty your water bottle before security, squeeze your toiletries into travel-size containers, and save anything bigger for your checked bag.
But the rule isn’t quite as simple as it sounds.
TSA actually allows several types of liquids over 3.4 ounces through airport security. Some of the exceptions are pretty practical, especially if you’re traveling with a baby or need medication, while others are a little more surprising.
So before you automatically toss something or move it to your checked luggage, here are the exceptions worth knowing.
First, here’s the normal TSA liquids rule
Under TSA’s 3-1-1 liquids rule, liquids, aerosols, gels, creams and pastes in your carry-on generally need to be in containers of 3.4 ounces or less. All of those containers should fit inside one quart-sized clear plastic bag, with one bag allowed per passenger.
That covers many of the things you’d normally pack in your bathroom bag, along with drinks and other liquid or gel foods. But there are some important exceptions.
Frozen liquids can be larger than 3.4 ounces
Here’s one of the more surprising exceptions: TSA allows frozen liquids and gel packs through security if they’re completely frozen solid when you present them for screening.
The catch is that they really do need to be frozen. If your bottle is partially melted, slushy or has liquid collecting at the bottom, it has to meet the regular 3-1-1 requirements unless it qualifies for another exception.
That means you could potentially freeze a full bottle of water before leaving for the airport and take it through security. The problem, of course, is getting it there before it starts melting.
Breast milk and formula don’t have to follow the 3.4-ounce limit
Parents have a much more useful exception. TSA allows breast milk and baby formula in quantities over 3.4 ounces in carry-on luggage, and they don’t have to fit in your quart-sized liquids bag.
TSA considers these medically necessary liquids, and you don’t even need to have your child traveling with you to bring breast milk or formula through security. Tell the TSA officer at the beginning of screening and remove them from your bag so they can be screened separately.
Toddler drinks and baby food get an exception too
The exception isn’t limited to breast milk and formula. TSA also allows toddler drinks and baby and toddler foods, including puree pouches, in quantities greater than 3.4 ounces.
These items may need additional screening, so let the TSA officer know what you’re carrying before your bag goes through. TSA also allows reasonable quantities of water for babies through the checkpoint.
Ice packs for breast milk and formula are allowed
If you need to keep breast milk, formula, toddler drinks or baby food cold, the ice packs and freezer packs you use to keep them chilled are also allowed in your carry-on. TSA specifically says this applies even when breast milk isn’t present.
And unlike the frozen-water exception, medically necessary gel ice packs don’t necessarily have to remain completely frozen. TSA says these cooling accessories can be allowed even when they’re melted or slushy, although they may require additional screening.
Medically necessary liquids can also be over 3.4 ounces
If you travel with liquid medication or another medically necessary liquid, you aren’t necessarily limited to a tiny travel-size container. TSA allows medically necessary liquids, medications, gels, aerosols and creams in reasonable quantities greater than 3.4 ounces.
They don’t have to go in your regular quart-sized liquids bag, but you should tell the TSA officer at the start of screening and expect them to be screened separately. TSA notes that medically necessary liquids may require additional inspection.
Even some drinks can qualify for medical reasons
The medical exception can go beyond something labeled as medicine. TSA says that if a medical condition requires it, a traveler may bring a juice box or another liquid over 3.4 ounces through security.
Again, this isn’t a way to bring an oversized drink simply because you want one for the flight. The liquid needs to be medically necessary and should be declared to TSA for screening.
And here’s probably the strangest exception: water for live fish
This one probably won’t help on your next family vacation, but it’s a good example of just how many exceptions there are to the rule. TSA allows live fish in water through the checkpoint when they’re in a clear, transparent container and a TSA officer inspects them.
Live coral in water is also listed as an allowed carry-on item after inspection. So while your bottle of water may be limited to 3.4 ounces, the water your fish is swimming in gets different treatment.
The 3.4-ounce rule has more exceptions than you might think
For everyday toiletries, drinks and other liquids, you should still plan around TSA’s regular 3-1-1 rule. A full-size bottle of shampoo doesn’t suddenly become okay simply because there are exceptions for other liquids.
But if you’re traveling with breast milk, formula, baby food, medically necessary liquids, or something that can stay completely frozen until screening, you may be able to bring considerably more than 3.4 ounces.
And if you’re ever unsure about a specific item, TSA has a searchable What Can I Bring? tool that lets you check the rules before you pack.
