When Should You Avoid Eating Fish? A Comprehensive Guide

November 7, 2025 •

3 min read

According to the FDA and EPA, most Americans can safely eat 2 to 3 servings of fish weekly, but some individuals and situations require caution. Knowing when to avoid eating fish is crucial for your health and safety, protecting you from harmful contaminants like mercury, dangerous bacteria, and allergic reactions.

Quick Summary

This guide explains the key situations and health conditions where eating fish is ill-advised, including pregnancy, young children, allergies, and weakened immune systems. It covers how to identify spoiled seafood and the risks associated with high mercury species or raw preparations.

Key Points

High-Risk Groups: Pregnant women, breastfeeding mothers, young children, older adults, and those with weakened immune systems should be cautious about fish consumption due to mercury and bacterial risks.
Avoid High-Mercury Fish: Stay away from species like shark, swordfish, king mackerel, and tilefish, which accumulate high levels of mercury that can harm the nervous system.
Cook Thoroughly or Avoid Raw: Raw or undercooked seafood can contain bacteria and parasites. Thorough cooking is essential, and high-risk individuals should avoid raw shellfish and sushi.
Check for Spoilage: Never eat fish that has a strong, sour, or ammonia-like smell, dull eyes, or slimy, mushy flesh, as cooking won't eliminate dangerous toxins.
Be Mindful of Allergies: If you have a fish or shellfish allergy, complete avoidance is necessary, as cooking does not destroy the allergenic proteins.
Consult Local Advisories: When eating local, wild-caught fish, always check for current advisories from environmental or health agencies regarding pollutants.
Manage Omega-3 Intake: If avoiding certain fish, use alternatives like flaxseeds or walnuts to ensure you still get beneficial omega-3 fatty acids.

Key Factors Affecting Fish Consumption Safety

While fish is a healthy part of many diets, rich in omega-3s, protein, and other nutrients, it's not always safe for everyone. Several factors determine whether you should exercise caution or avoid it entirely, with the primary concerns being contamination, spoilage, and individual health conditions.

High Mercury Content

Mercury is a neurotoxin that can accumulate in fish over time. Large, longer-lived predatory fish tend to have the highest levels through a process called biomagnification.

Who should avoid high-mercury fish? Pregnant and breastfeeding women, those trying to become pregnant, and young children are most vulnerable because mercury can harm a developing nervous system.
Common culprits: The FDA and EPA advise that these groups should completely avoid fish such as shark, swordfish, king mackerel, and tilefish.
Safe alternatives: They can, however, enjoy 2 to 3 servings of low-mercury options like salmon, canned light tuna (limited), and pollock each week.

Foodborne Illness and Parasites

Raw or undercooked seafood can harbor harmful bacteria and parasites, posing a serious risk of food poisoning.

Raw shellfish: Oysters, clams, and mussels that are raw or not thoroughly cooked can carry bacteria like Vibrio vulnificus or viruses such as norovirus. Individuals with compromised immune systems, including older adults and pregnant women, are particularly at risk.
Scombroid poisoning: This allergy-like reaction is caused by a toxin (histamine) produced by bacteria in certain fish, like tuna and mackerel, when they are not refrigerated properly. This toxin is heat-resistant, so cooking will not make contaminated fish safe.
Parasites: The rise in popularity of raw fish dishes like sushi has led to an increase in parasite infections, such as anisakiasis from nematodes (worms). Freezing at specific temperatures is required to kill these parasites, and not all domestic freezers are adequate for this purpose.

Seafood Allergies

Fish and shellfish allergies are relatively common and can cause severe, sometimes life-threatening, reactions. A person allergic to one type of seafood may also react to others. Unlike with some other allergies, cooking seafood does not eliminate the proteins that cause the allergic response. For individuals with a diagnosed fish or shellfish allergy, complete avoidance is necessary.

Comparison of Common Fish and Seafood Risks


Fish/Seafood Type	Primary Concern	High-Risk Groups	Key Precautions
Shark, Swordfish, Marlin	High Mercury	Pregnant/breastfeeding women, young children	Avoid completely
Canned Light Tuna	Low Mercury	General population	Limited portions for pregnant/breastfeeding women
Raw Oysters/Shellfish	Bacteria, Viruses	Immunocompromised, pregnant, elderly	Avoid completely or cook thoroughly
Farmed Salmon	Low Contaminants	Most individuals	Monitor reputable sourcing
Wild Fish (local catch)	Environmental Pollutants	All individuals	Check local health advisories
Tuna, Mackerel (Scombroid)	Histamine Poisoning	All individuals	Ensure proper refrigeration and handling

How to Identify Spoiled Fish

Eating spoiled fish can lead to food poisoning. Knowing the signs is your first line of defense.

Smell: Fresh fish has a mild, clean, oceanic smell. A strong, fishy, sour, or ammonia-like odor is a clear sign of spoilage and requires immediate disposal. Cooking does not eliminate the odor or make it safe.
Appearance: Fresh fish has bright, clear, and shiny skin, often with bright red gills. A spoiled fish will have dull, faded skin, cloudy or sunken eyes, and brown or grey gills.
Texture: The flesh of fresh fish is firm and elastic, springing back when pressed. Spoiled fish will have soft, mushy, or slimy flesh that indents easily.

Conclusion: Make Informed Choices for Safer Eating

While seafood offers significant health benefits, understanding the potential risks is paramount. By being aware of high-mercury species, recognizing the dangers of raw preparations for certain individuals, and learning to identify signs of spoilage, you can protect yourself and your family. Always check for local fishing advisories if you consume wild-caught fish. The key is to make mindful choices, prioritizing safety and sourcing from reputable vendors to ensure a healthy and enjoyable experience with seafood.

A note on dietary choices

Fish is an important source of nutrients, especially for cardiovascular health. However, people with conditions like mercury sensitivity or specific allergies need alternatives. For those who need to limit fish, plant-based sources of omega-3s, such as walnuts, flaxseeds, and chia seeds, can be great substitutes.

For more detailed guidance on seafood safety and federal recommendations, visit the official FoodSafety.gov website.

Frequently Asked Questions

No, cooking does not remove or reduce the mercury content in fish. Mercury is stored in the fish's tissue, not just on the surface, and will remain after cooking. The only way to avoid mercury is to limit or avoid high-mercury species.

Use your senses. Fresh fish should smell mild and clean, not sour or strongly 'fishy'. Look for firm, shiny flesh, and clear, bright eyes. If the flesh is mushy, the eyes are cloudy, or there is a thick, milky slime, the fish is likely spoiled.

Pregnant women should choose low-mercury fish. The FDA lists salmon, shrimp, pollock, and canned light tuna (in moderation) as 'best choices'. They should avoid all high-mercury and raw seafood.

Scombroid poisoning is a reaction caused by histamine from bacteria in improperly stored fish like tuna and mackerel. To avoid it, ensure all fish is kept properly refrigerated or on ice. It is important to note that this toxin is not destroyed by cooking.

Yes, but with caution. Children should follow the same guidelines as pregnant women, sticking to low-mercury fish and avoiding species like shark, swordfish, and marlin. Parents should also avoid giving them raw seafood to prevent food poisoning.

Freezing can kill parasites, but it does not kill all bacteria. For example, the parasite Anisakis is killed by commercial freezing at specific temperatures, but this does not guarantee safety from bacterial contamination.

Generally, fresh, raw fish should be cooked and consumed within two days of purchase if stored in a refrigerator. Cooked fish leftovers are typically safe for up to three days.