Is it safe to eat fish skin or crab and lobster entrails (tomalley)? —J.P., Alexandria, Va.

You should probably skip both. Toxins such as PCBs and dioxin can concentrate in the skin, fat, and internal organs of fish. Trim away both the skin and the darker, fatty portions of flesh before cooking. And you should avoid eating tomalley, the greenish substance in a crustacean's gut that serves as a liver and pancreas, even though some people consider it a delicacy. Though it might often be safe, it can contain toxins that filter in from polluted habitats. The Food and Drug Administration warned against eating lobster tomalley in the summer of 2008 due to high levels of a naturally occurring toxin likely stemming from red tides, or dangerous algal bloom.

Read more about fish risks and how to cut your risk of food-borne illness.