Most clams, and other bivalves, have clear blood, but the blood clam's blood contains hemoglobin. Which makes it subject to the blood diseases that afflict humans. Blood clams from China have been banned because they were found to have hepatitis.

Why are blood clams dangerous?

Blood Clams.

Unlike other varieties of clams that are safe to eat, the blood clam can ingest viruses and bacteria including hepatitis A, typhoid and dysentery because it lives in lower oxygen environments.

What do clams have instead of blood?

Most clams lack haemoglobin in their blood, the protein molecule that gives our blood it's colour. Blood Clams though, do contain haemoglobin. This gives them both their somewhat gruesome appearance when opened, often oozing blood all over the unlucky individual.