If you’ve ever found yourself standing in a TSA line, digging through your carry-on because you forgot about a full-size bottle, you’re definitely not the only one. The 3.4-ounce rule is so familiar that many travelers assume it applies to every liquid they bring on a plane.

It doesn’t.

The TSA has several exceptions for liquids, gels, creams, and other items that may be needed for medical reasons, for a baby or young child, or for certain special circumstances. These items can often be carried in amounts larger than 3.4 ounces, though they may need extra screening.

Here are some of the exceptions worth knowing before your next flight.

Breast Milk, Baby Formula, and Baby Food

Traveling with a baby comes with enough planning already, so parents don’t have to squeeze every bottle of formula or container of baby food into a tiny quart-sized bag.

Breast milk, infant formula, toddler drinks, baby food, and puree pouches can be brought through security in reasonable quantities for the trip. Ice packs, freezer packs, and gel packs used to keep these items cold are also permitted.

Tell the TSA officer about these items before screening begins. They may need to be inspected separately.

One detail that surprises some parents: TSA says the breast milk and formula exception can apply even if the child isn’t traveling with you.

Prescription and Medically Necessary Liquids

Medication is another major exception to the standard liquid limit. Travelers can bring prescription medications and many other medically necessary liquids in containers larger than 3.4 ounces when they’re needed during the trip.

This can include liquid prescription drugs, cough medicine, liquid pain relievers, saline solution, and other treatments. Medical supplies used with these products, such as syringes, IV bags, feeding tubes, and pumps, may also be allowed.

Keep these items easy to reach in your carry-on and tell the TSA officer about them before screening. Additional inspection may be required, so having them separated from the rest of your belongings can make the process easier.

Liquid Nutritional Supplements

Some travelers rely on liquid nutritional drinks, meal-replacement beverages, or other nutritional products for medical or dietary reasons.

If you need more than 3.4 ounces for your trip, these products may qualify for an exception. They can receive additional screening, so let the TSA officer know about them before your bag goes through the checkpoint.

Toddler Drinks

Milk, juice, and other drinks for toddlers can also be brought through airport security in quantities above the usual limit when they’re needed for the child during the trip.

Keep these drinks together with the other baby or toddler supplies in your carry-on. Tell the TSA officer about them before screening starts so there’s no confusion about why you’re carrying larger containers.

Ice and Gel Packs for Medical or Baby Items

Need to keep breast milk, formula, baby food, or medication cold during a trip? Ice packs, freezer packs, and gel packs can qualify for an exception when they’re being used for these purposes.

It’s helpful to keep the packs frozen or partially frozen when you reach security. Let the TSA officer know what they’re being used for, since they may be inspected separately.

Frozen Water Bottles

A frozen bottle of water can be a handy way to bring water through security without carrying a bottle full of liquid.

The key is that the water needs to be completely frozen when you go through the checkpoint. If the ice has started melting and there’s liquid water in the bottle, the standard liquid rules can apply.

So if you try this trick, take the bottle straight from the freezer and head to security before it has time to thaw.

Contact Lens Solution

Contact lens solution is another item that can qualify for an exception when a traveler needs more than 3.4 ounces.

Keep the solution in your carry-on and tell the TSA officer that you’re carrying it for your contact lenses. It may receive additional screening before being allowed through.

If you don’t need a large bottle, packing a travel-sized container can still save time at the checkpoint.

Frozen Gel Packs

Frozen gel packs can sometimes pass through security when they’re completely frozen. Once a gel pack begins to thaw and contains liquid, the regular liquid restrictions may apply.

If you’re bringing one through security, keeping it frozen until screening is the safest bet. If it’s being used to keep medication, breast milk, or baby food cold, mention that to the TSA officer.

Live Fish, Coral, and Other Aquatic Animals

This one catches many travelers by surprise. Certain live aquatic animals can be brought through TSA screening in water, including live fish, coral, and live lobsters.

The animals need to be transported in clear, leak-proof containers so TSA officers can inspect them. A larger container may be allowed because the water is necessary for transporting the live animal.

If you’re planning to fly with live aquatic animals, don’t wait until you’re standing at the checkpoint to figure everything out. Travelers should notify TSA before screening begins.

You’ll also want to check your airline’s rules ahead of time. An item being permitted through TSA security doesn’t automatically mean every airline will accept it for transport.

Knowing these exceptions can save you from throwing away perfectly good items at the airport or trying to squeeze something necessary into a tiny container. The standard 3.4-ounce rule still applies to most liquids in carry-on bags, but there are several situations where larger amounts are allowed.

If you’re unsure about a particular item, check the TSA’s current guidance before leaving for the airport. Rules can change, and a quick check before your trip is much easier than finding out at the security checkpoint.