The Travel Toiletry Kit & TSA 3-1-1

The 3-1-1 rule, decoded

For carry-on bags, security rules in most of the world come down to the same three numbers: liquids and gels in containers of 100 ml (3.4 oz) or less, all fitting in one quart-size (litre) clear resealable bag, one bag per passenger. The tripwires:

• The container size is what counts, not the contents. A half-empty 200 ml tube fails.
• Pastes and creams are liquids — toothpaste, sunscreen, deodorant cream, peanut butter. If it spreads, it counts.
• Medications and baby formula are exempt in reasonable quantities — keep them accessible and declare them.
• Larger bottles are fine in checked luggage — inside a zip-top bag, because pressure changes make bottles burp.

Solid swaps: skip the rules entirely

Every liquid you replace with a solid is one less thing in the quart bag: shampoo and conditioner bars (a good bar outlasts three flights' worth of minis), bar soap in a ventilated case, toothpaste tablets, solid deodorant, and laundry sheets for sink washing on longer trips. A typical kit gets down to two or three true liquids — which fit in refillable silicone bottles with room to spare.

What actually goes in the kit

Toothbrush (a cover or case keeps it off hostel sinks), toothpaste, floss; bar soap or body wash; shampoo (bar or decanted); deodorant; razor; sunscreen (travel size — buy the big bottle at the destination); lip balm with SPF; nail clippers; pain reliever, antihistamine, and band-aids; plus your prescriptions — the one category that must stay in original labeled containers and in your carry-on. A quick-dry microfiber towel rounds it out for hostels, beaches, and gyms.

Skip: full-size anything, the "free hotel stuff" stockpile, and a first-date quantity of cosmetics. If you didn't use it on the last two trips, it leaves the kit.

Related guides

• Carry-On Only: How to Pack a Week in One Bag
• Sun Protection for Travelers
• All Gear Guides