Yes, you can bring toothpaste on a United Airlines flight, but there are size restrictions for carry-on luggage. Here’s the breakdown:
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Carry-on Baggage: Toothpaste is allowed in your carry-on bag, but it must be in a container that is 3.4 ounces (100 milliliters) or less. All your liquids, gels, and aerosols must fit in a single, quart-sized, clear plastic, zip-top bag. This is the TSA’s 3-1-1 liquids rule. 
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Checked Baggage: You can pack full-size toothpaste tubes in your checked baggage without any size restrictions. 
Tips:
- Travel-sized toothpaste: Buy travel-sized toothpaste tubes to comply with the TSA regulations.
- Solid toothpaste: Consider solid toothpaste bars or tablets as an alternative to avoid liquid restrictions.
- Check with TSA: If you have any doubts, you can always check the TSA website (tsa.gov) or contact them directly for the most up-to-date information on allowed and prohibited items.
Have a great flight! ✈️