For aviation security purposes, the definition of a "liquid" is much broader than the scientific one, following the general rule: "If you can pour it, pump it, squeeze it, or spread it, it’s a liquid." This includes obvious items like water, shampoo, and perfume, but also "semi-liquids" or gels such as toothpaste, hair gel, lip gloss, and mascara. Even food-based toiletries or items with a similar consistency like peanut butter, jam, or yogurt are treated as liquids. Creams and lotions (including sunscreen and moisturizer) and aerosols (like shaving cream or deodorant spray) also fall under this category. Under the standard "3-1-1" rule (or the 100ml rule), each of these items must be in a container of 100 milliliters (3.4 ounces) or less and fit into a single, quart-sized, clear plastic zip-top bag. Some modern airports in 2026 equipped with advanced CT scanners may allow you to keep these in your bag, but the 100ml volume limit usually still applies for security reasons. Solid items like bar soap, stick deodorant, or powder foundation are not classed as liquids and can be carried in any quantity without being placed in the clear plastic bag.