Fish bone is the most common food-related
foreign body to cause
airway obstruction.
Choking on fish was responsible for about 4,500 reported accidents in the
United Kingdom in 1998.
Allergens A
seafood allergy is a
food allergy to
allergens which can be present in
fish. This can result in an
overreaction of the
immune system and lead to severe physical symptoms from
urticaria to
angioedema and
distributive shock. Allergic reactions can result from ingesting seafood, or by breathing in vapours from preparing or cooking seafood. The most severe allergic reaction is
anaphylaxis, a
medical emergency requiring immediate attention and is treated urgently with
epinephrine.
Biotoxins , Japan Some species of fish, notably the
fugu pufferfish used for
sushi, can result in serious
food poisoning if not prepared properly. These fish always contain
toxins as a
natural defense against
predators; it is not present due to environmental circumstances. Particularly,
fugu has a lethal dose of
tetrodotoxin in its
internal organs and must be prepared by a licensed
fugu chef who has passed the national examination in Japan.
Ciguatera poisoning can occur from eating larger fish from warm tropical waters, such as
sea bass,
grouper,
barracuda and
red snapper.
Scombroid poisoning can result from eating large oily fish which have sat around for too long before being refrigerated or frozen. This includes
scombroids such as
tuna and
mackerel, but can also include non-scombroids such as
mahi-mahi and
amberjack.
Shellfish are
filter feeders and, therefore, accumulate
toxins produced by microscopic
algae, such as
dinoflagellates and
diatoms, and
cyanobacteria. There are four syndromes called
shellfish poisoning which can result in humans,
sea mammals and
seabirds from the ingestion of toxic shellfish. These are primarily associated with
bivalve molluscs, such as
mussels,
clams,
oysters and
scallops. Fish like
anchovies can also concentrate toxins such as domoic acid. If suspected, medical attention should be sought. The toxins responsible for most shellfish and fish poisonings, including ciguatera and scombroid poisoning, are heat-resistant to the point where conventional cooking methods do not eliminate them. According to the
US Food and Drug Administration (FDA), the risk from mercury by eating fish and shellfish is not a health concern for most people. However, certain seafood contains sufficient mercury to harm an unborn baby or young child's developing nervous system. The FDA makes three recommendations for child-bearing women and young children: • Do not eat
shark,
swordfish,
king mackerel, or
tilefish because they contain high levels of mercury. • Eat up to 12 ounces (2 average meals) a week of a variety of fish and
shellfish that are lower in mercury. Four of the most commonly eaten fish that are low in mercury are
canned light tuna,
salmon,
pollock, and
catfish. Another commonly eaten fish,
albacore ("white tuna") has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week. • Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but do not consume any other fish during that week. These recommendations are also advised when feeding fish and shellfish to young children, but in smaller portions.
Persistent organic pollutants If fish and shellfish inhabit
polluted waters, they can accumulate other toxic chemicals, particularly fat-soluble pollutants containing
chlorine or
bromine,
dioxins or
PCBs.
Parasites Parasites in fish are a common natural occurrence. Though not a health concern in thoroughly cooked fish, parasites are a concern when consumers eat raw or lightly preserved fish such as
sashimi,
sushi,
ceviche and
gravlax. The popularity of such raw fish dishes makes it important for consumers to be aware of this risk. Raw fish should be frozen to an internal temperature of for at least 7 days to kill parasites; home
freezers may not be cold enough. Historically, fish that live all or part of their lives in
fresh water were considered unsuitable for sashimi due to the possibility of parasites (see
Sashimi article). Parasitic infections from freshwater fish are a serious problem in some parts of the world, particularly
Southeast Asia. Fish that spend part of their life cycle in
brackish or fresh water, like
salmon (an
anadromous coastalfish closely related to
trout), are a particular problem. A study in
Seattle, Washington showed that 100% of wild salmon had
roundworm larvae capable of infecting people. In the same study
farm-raised salmon did not have any roundworm larvae. Parasite infection from raw fish is rare in the
developed world (fewer than 40 cases per year in the
United States), and involves mainly three kinds of parasites:
Clonorchis sinensis (a
trematode/
fluke),
Anisakis (a
nematode/roundworm) and
Diphyllobothrium (a
cestode/
tapeworm). Infection risk of
Anisakis is particularly high in fish which may have lived in a river or estuary, such as salmon (
sa ke in
Japanese cuisine) or
mackerel (
sa ba in Japanese cuisine). Such parasite infections can generally be avoided by
boiling,
grilling,
preserving in salt or vinegar, or deep-freezing. In Japan, it is common to eat raw salmon and
ikura (
roe), but these foods are frozen overnight prior to eating to prevent infections from parasites, particularly
Anisakis. ==Pescetarianism==