Shampoo, in limited quantities, is generally allowed on airplanes in carry-on luggage, but pressurized containers of dry shampoo are often prohibited due to the risk of explosion.
Here's a breakdown:
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Liquids Rule: The TSA's "3-1-1 rule" dictates that liquids, including shampoo, in carry-on luggage must be in containers of 3.4 ounces (100 milliliters) or less. These containers must then be placed in a single, clear, quart-sized bag. This rule is in place for security reasons.
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Dry Shampoo Exception: Dry shampoo often comes in aerosol cans, which are pressurized. According to the reference, these pressurized containers are restricted, or even banned, because the change in air pressure in the airplane cabin can cause them to explode. This presents a safety hazard.
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Checked Baggage: Larger quantities of regular liquid shampoo are permitted in checked baggage. However, even in checked baggage, it's wise to avoid aerosol cans or to take measures to prevent leaks and spills due to pressure changes (such as placing them in sealed bags).
In Summary: While regular shampoo is permitted in small quantities in carry-on luggage, pressurized containers, especially those containing dry shampoo, are often prohibited due to the risk of explosion caused by changes in air pressure.
