Can you take a 4 fl oz unopened bottle of benadryl on a flight?

Yes, you can take an unopened 4 fl oz bottle of Benadryl on a flight, but it must comply with the Transportation Security Administration (TSA) liquid regulations. This means it should be packed in your carry-on luggage and placed in a quart-sized bag along with other liquids, gels, or aerosols. Each container must be 3.4 fl oz (100 ml) or less. Always check the latest TSA guidelines before traveling, as regulations may change.