Many countries have restrictions on what you can bring into that country. These restrictions may include food, pets, and medications. Even some over-the-counter medications are not allowed in some countries. Check the Country Information page for your destination to find contact information for its embassy or consulate in the United States. Visit their website to find out what items are not allowed.
Customs Restrictions in Foreign Destinations – What You Cannot Take out of Other Countries
Some countries may not allow you to take certain items out of the country. These items may include:
Countries may require export permits, which may take time to process. If you violate foreign customs rules, you may be detained at the airport and fined. You may also have your items confiscated, and, in some cases, you may be prosecuted and/or sentenced to prison.
U.S. Customs Restrictions – What You Cannot Bring Into the United States
You cannot bring some items into the United States. There are also items that you can bring in only under certain conditions. See the Customs and Border Protection page "Know Before You Go" for more information. For a list of items not allowed to enter the United States, see the Customs and Border Protection website.
Also check out the CBP video Declaration of Agricultural Items on Entry
For more information on wildlife and wildlife products, contact the U.S. Fish and Wildlife Service.
For more information on rules regarding dogs entering the United States, please check the CDC website on importing dogs.