Shellfish poisoning is the illness caused by eating shellfish contaminated with natural marine biotoxins, the same condition as paralytic shellfish poisoning in its most notorious form. Filter-feeding bivalves, mussels, clams, oysters, and scallops, concentrate toxins produced by algal blooms, and cooking does not destroy them. Paralytic poisoning brings tingling, numbness, and in severe cases respiratory paralysis; related syndromes cause diarrhoea, vomiting, memory loss, or neurological symptoms depending on the toxin. There is no antidote, so prevention is everything: harvesting waters are monitored, beds are closed during toxic blooms, and commercial shellfish are tested before sale. Gathering wild shellfish from unmonitored shores is the classic route to poisoning.