Bringing hair color on a flight in 2026 depends entirely on its chemical composition and where you pack it. Liquid or cream hair dye is allowed in carry-on bags as long as it adheres to the "3-1-1" rule (containers must be 3.4 oz / 100 ml or less and fit in a quart-sized bag). However, you must be extremely careful: many hair dyes contain peroxide or "oxidizing" chemicals, which are technically classified as hazardous materials. In some airports, security officers may prohibit large quantities of professional-grade dye in carry-ons due to these "oxidizer" risks. In checked baggage, you can typically bring full-sized kits, but it is highly recommended to double-seal them in Ziploc bags, as the pressure changes in the cargo hold can cause the tubes to burst, potentially ruining your entire wardrobe. Aerosol hair color sprays (like root touch-ups) are generally allowed in checked bags under the "toiletry" exception, provided they have a protective cap. If you are traveling with high-end, expensive color, your safest bet is to pack it in your checked luggage to avoid the stringent liquid volume limits at the security checkpoint.