To bring skincare in your carry-on, you must follow the global 3-1-1 rule. This means every liquid, gel, cream, or aerosol—including serums, moisturizers, and sunscreens—must be in a container that is 3.4 ounces (100ml) or smaller. Even if a bottle is only half full, if the original packaging says "5 oz," security will likely confiscate it. All these small containers must fit into a single, clear, quart-sized (1 liter) resealable bag. If you have a multi-step routine with large bottles, you should either decant them into travel-size jars or pack the full-sized items in your checked luggage, where there are no volume limits. The only exceptions to the 3-1-1 rule for carry-ons are medically necessary liquids (like certain medicated creams) or baby care items, which should be declared to the security officer before you begin the screening process to avoid delays.