Spend enough time trying to understand the TSA’s rules for liquids, and you might fall into an existential rabbit hole. Just what is a liquid, anyway? And since when is peanut butter a gel? It’s normal to be overwhelmed by the differences between rules for checked bags and carry-on bags and by the packing requirements for liquids, gels and aerosols. No wonder travelers have so many questions.

Making Sense of 3-1-1

The 2006 introduction of the 3-1-1 rule changed the way travelers pack liquids, gels and aerosols. While they can be packed in any quantities in checked bags, these substances are subject to the TSA’s restrictions when they’re packed in carry-on bags. Basically, the TSA limits the quantities of liquids, gels and aerosols that are allowed in the cabin of the plane, but not in the baggage area.

Some travelers think that the 3-1-1 rule includes specific restrictions for different items. That’s not the case; the rule doesn’t set a maximum for, say, how many ounces of toothpaste is allowed on a plane. What the 3-1-1 rule says is that any liquids, gels and aerosols that you plan to pack in a carry-on bag must be in containers no larger than 3.4 ounces (100 milliliters). All containers must fit into a 1-quart clear, resealable bag, and each passenger is limited to one bag. TSA agents strictly enforce these rules. The only exceptions are made for medically necessary liquids or substances that are required to feed a baby.

The name of the rule can help you remember these restrictions.

  • 3: Each container must be no larger than 3.4 ounces.
  • 1: All containers must fit into a 1-quart bag.
  • 1: Each passenger may have one bag of liquids, gels or aerosols in his or her carry-on.

Packing Liquids in Checked Baggage

Go ahead – stuff those souvenir snow globes, full-size perfume bottles and supersized tubes of sunscreen into your checked bags. The TSA doesn’t impose any liquid limits on checked bags, with the exception of hard alcohol (more on that in a minute). For travelers packing liquids in checked baggage, the major concern should be preparing these containers, so they don’t explode during your flight and ruin everything else in the suitcase.

To leak-proof containers of liquids, gels and aerosols, gather together some plastic bottles and plastic wrap. Remove the caps of all your shampoo bottles and other containers; cover the openings with plastic wrap and screw the caps back on. Even if the caps come ajar, the plastic wrap should contain the substance inside. Place each liquid, gel or aerosol product inside its own plastic bag with a leak-proof seal. Pack the bags in a packing cube or toiletry case and nestle the bag into the middle of the suitcase so it’s cushioned by clothing.

Liquid or Not: Making Assessments

Unsure if something on your packing list qualifies as a liquid, gel or aerosol? A good way to figure it out is to think about the item’s consistency. A substance that’s spreadable, “smearable,” “sprayable” or “squirtable” is subject to the 3-1-1 rule. Peanut butter, toothpaste, sunscreen, applesauce, dry shampoo: They all count.

Note that different versions of the same product may be categorized differently. For example, stick deodorant is not considered a liquid, gel or aerosol and neither is powdered deodorant. But gel, spray or roll-on deodorants do count toward your liquids limit. Similarly, spray-on perfume or cologne counts as a liquid, but a solid fragrance does not.

Some travelers don’t realize that the TSA liquids rules don’t only apply to toiletries and food or drinks. Glow sticks, liquid vitamins, filled cartridges for e-cigarettes and other vaping devices, hand sanitizer and wet pet food are some other common items that must be packed in accordance with the 3-1-1 rule. Gel packs or ice packs count as liquids unless they’re frozen solid when you reach the TSA security checkpoint.

Using Medical Exceptions

Those passengers with medical conditions need not panic about their supplies and medications being confiscated. The TSA strives to accommodate the health needs of all travelers. Basically, it’s fine to pack any medications and medical accessories in your carry-on bag, even if they’re liquids, gels and aerosols in amounts larger than are allowed under the 3-1-1 rule.

That means travelers with diabetes may pack syringes, insulin, ice packs and testing supplies in their carry-on bag without worrying that they will be confiscated. Passengers with certain heart conditions can carry their nitroglycerin tablets and sprays past security. Medically-necessary prescription creams should be fine too.

Keep in mind that TSA agents still need to screen all your medications and medical supplies, just as they screen everything passengers carry. Pack these supplies in whatever way makes sense for you (no need to pack medically-necessary liquids in a 1-quart plastic bag) and let an agent know about them when you arrive at the checkpoint. Agents can screen medications by hand if you prefer them not to exposed to X-rays.

Making Exceptions for Babies

The littlest airplane travelers won’t go hungry because of the TSA’s liquids rule. Parents or guardians traveling with infants or young toddlers – basically, any child who is too young to walk through the body scanner alone – may bring breast milk, formula and juice in quantities exceeding the 3-1-1 limits. Water for making a baby’s formula is allowed too. And there’s good news for moms who pump breast milk while away from home: Parents traveling with breast milk may take it through security in large quantities, even if no child is present.

The ice pack requirements don’t apply to passengers taking advantage of this exception. Normally, they would count toward your liquid limit if they were even slightly slushy when the TSA checks them, but ice or gel packs that are keeping a child’s food or drink cold during travel don’t have to be frozen solid when you reach security.

Baby food is also allowed through the checkpoint in “reasonable amounts.” Stuff a carry-on with as many jars or pouches of baby food as you expect the child to go through during the trip. Note that these exceptions don’t apply to all baby products. Travelers who pack items like large tubes of diaper cream and full bottles of baby shampoo should put them in a checked bag.

Taking Makeup on the Plane

People who wear makeup tend to experience the most difficulties in navigating the TSA’s liquid rules. Some of the products you’d like to pack probably have consistencies that are somewhere between a liquid and a solid, such as creamy blushes and lip stains, and it doesn’t take many products to fill that 1-quart bag to the gills.

First things first: Mascara is considered a liquid on a plane, and so is lip gloss, liquid eyeliner and liquid foundation (of course), nail polish, moisturizer and other cosmetics with squirtable, spreadable textures. Baby wipes and makeup removal wipes don’t count as liquids, so they can go into your carry-on bags in any quantity.

One way to avoid the 3-1-1 limit is to pack your makeup bag in a checked bag and stick just a few travel essentials, such as a miniature bottle of hydrating facial mist and tubes of concealer and lip gloss, into the 3-1-1 bag for the purpose of post-flight freshening up. Flying is also a convenient time to try out sample versions of makeup products, which don’t take up much room in a 1-quart bag. If you can’t be without your makeup essentials but don’t want to check a bag, try out some solid versions of common cosmetics. Take powder blush and foundation instead of creamy versions, opt for a lip pencil instead of gloss and pick up a pot of solid perfume instead of packing the liquid stuff.

Traveling With Alcohol

Headed to a party, or bringing the party home with you? Either way, TSA agents won’t stop you – or judge you – if they find alcohol in carry-on or checked bags. As long as alcohol packed in carry-on bags conforms to the 3-1-1 rule, the TSA has no objections. So feel free to pack that 1-quart bag full of mini alcohol bottles, but note that airlines don’t want passengers pouring their own drinks onboard for safety reasons.

Alcohol is also allowed in checked bags. Tuck a few bottles of wine in among your clothes, or fill a suitcase with nothing but beer; either way, the TSA approves. For beverages that have between 24 percent and 70 percent alcohol, aka hard liquor, each traveler may pack up to 5 liters in checked bags. Any booze that’s more than 70 percent alcohol is banned on a plane traveling within the United States. Alcohol regulations for luggage vary by country; for example, the EU has a set of standard maximums but allows each country to set its own alcohol limits.

Following TSA Rules for Food

Because so many travelers think “liquids” when they think TSA restrictions, some people are stunned when they arrive at the TSA checkpoint and are made to throw away their snacks. Remember: Anything that’s smearable or spreadable counts toward your allowance of liquids, gels and aerosols. A thin layer of peanut butter spread between slices of bread probably won’t raise any alarms, but a tub or packet of the stuff will. The same goes with tubes of yogurt, cups of hummus and other creamy foods. They either have to fit into your 1-quart bag, or they can’t go through security.

TSA policy is constantly evolving, and agents now ask passengers to remove all food from their bags before screening. Like electronics and bags of liquids, gels and aerosols, solid food items have to be run through the X-ray separately. (Things are a little easier for members of TSA’s PreCheck program. They can leave electronics and liquids in their bags during screening.)

Powder-like substances in quantities greater than 12 ounces must also be removed from your carry-on for separate screening. If you’re traveling with protein powder, body powder, powdered instant coffee or anything else of a similar texture, check the package size before going to the airport to figure out whether or not it will have to be removed for screening.

Tips for Traveling With Liquids

Because packing liquids for travel can be something of a hassle, some travelers might want to avoid doing it altogether. Keep in mind that travel-size toiletries are widely available in grocery stores, drugstores and even hotel gift shops. If it’s possible to make a quick stop into one of these stores upon arriving at your destination, it might make sense to buy these small toiletries at the beginning of the stay. Use them up and discard any leftovers before flying home.

Alternately, buy a sturdy quart-size clear plastic case filled with travel-size bottles and fill them from your full-size toiletries at home. Leave the bag in your suitcase, so your staple products are always ready to go at the start of each trip without your having to gather and pack things like shampoo and face wash before each trip.

As you pack and head to the airport, questions might arise about specific items on your packing list. Download the MyTSA app, which includes a searchable database of common items that people fly with and provides information about any restrictions on those items. The app also makes it easy to access TSA customer service. When you have one of those “Can I bring this?” moments, connect with a real person who can give you the answer.