Whether you put toiletries in your suitcase (checked bag) or carry-on depends on their size and your convenience. In 2026, TSA and international regulations still enforce the 3-1-1 rule for carry-ons: liquids, gels, and aerosols must be in 3.4oz (100ml) containers or smaller, all fitting in one quart-sized bag. If your toiletries are larger than this—such as full-sized shampoo bottles, sunscreens, or large shaving creams—they must be packed in your checked suitcase. To prevent a "shampoo explosion" caused by cabin pressure changes, it is a "best practice" to squeeze excess air out of plastic bottles before sealing them and to place all liquid items inside a secondary leak-proof bag or a dedicated toiletry kit. Packing them in your suitcase also saves you the hassle of removing them during the security screening process at the airport.