Is It Safe to Eat Raw Fish? Parasite and Mercury Risks Explained

For most healthy adults, raw fish from a reputable restaurant is low risk. But it is not risk-free. The main concerns are parasites, bacteria and, for some species, mercury. Hong Kong's Centre for Food Safety classifies sushi and sashimi as high-risk foods.

The risks in brief. Parasites: killed by freezing — Codex: –20°C for 7 days or –35°C for about 20 hours; Tokyo guidance: –20°C for 24 hours at the core. Not effective: wasabi, soy sauce, vinegar, marinating. Bacteria: keep at or below 4°C. Mercury: highest in large predatory fish. Who should avoid raw fish: pregnant women, young children, older adults, people with weakened immunity.

Parasites

The best-known sushi parasite is Anisakis, found in fish such as mackerel, squid and salmon. The Centre for Food Safety says freezing and heat treatment are the most effective ways to kill parasites, and cites Codex guidance of freezing at –20°C or below for seven days, or –35°C for about 20 hours, for fish to be eaten raw. Tokyo's food safety centre says freezing for at least 24 hours at –20°C, until the centre is frozen, kills Anisakis.

What doesn't work

Tokyo's guidance notes that wasabi, soy sauce and vinegar in normal amounts do not kill Anisakis. The European Food Safety Authority, cited by the Centre for Food Safety, says traditional marinating and cold smoking are not enough either. So shime-saba (vinegared mackerel) should still use frozen fish.

Bacteria and temperature

Raw fish must stay cold. Keep it at or below 4°C; the 4°C to 60°C range is the danger zone where bacteria grow. Eat takeaway sushi quickly. See how to store sushi safely.

Mercury

The Centre for Food Safety advises that pregnant women, women planning pregnancy and young children avoid large predatory fish such as tuna (especially bigeye and bluefin), swordfish and shark. For most adults, moderate consumption of a variety of fish is recommended. See bluefin vs yellowfin.

Freshwater fish sashimi carries extra parasite risk. The Centre for Food Safety advises caution, and susceptible groups should not eat it at all.

Lower your risk: choose reputable restaurants · eat promptly · avoid fish left at room temperature · choose cooked options if you're in a high-risk group.

Symptoms of anisakiasis can include severe stomach pain, nausea and vomiting within hours of eating. See a doctor if this happens after eating raw fish.

Common questions

Does wasabi kill parasites?

No.

Is "sushi-grade" fish frozen?

Often, but there's no single legal definition — ask the supplier.

Where else can I look?

See sushi in pregnancy.

Compiled by our editorial team from Hong Kong Centre for Food Safety and Department of Health guidance, Tokyo Metropolitan Government food safety information, Codex references cited by the Centre for Food Safety, European Food Safety Authority findings and product information, retrieved September 2026. This is general information, not medical advice. If you are pregnant, have an allergy or a medical condition, follow your doctor's advice.