MICHAEL KEATING, M.D.,C.C.F.P., F.C.F.P.
(506) 696-0567
ANDREA CANTY, M.D., C.C.F.P., F.C.F.P.
(506) 696-0587
707 MILLIDGE AVE
SAINT JOHN, N.B.
E2K 2N7
Seafood allergies
Seafood allergies affect roughly 6.6 million Americans, according to the American
Academy of Allergy, Asthma and Immunology. Like other food allergies, seafood
allergies can be fatal if a person does not practice strict avoidance of all seafood
products. While most food allergies develop in young children and disappear as
they grow older, seafood allergies frequently remain throughout adulthood. In
fact, many people first develop seafood allergies as adults.
The most serious type of allergic reaction to seafood involves a response known
as anaphylactic shock. This potentially fatal condition can be triggered by even
a very small amount of a seafood protein.
There are three types of seafood that can trigger allergic reactions:

Fish. There are two main categories of fish: “bony fish” (e.g., salmon, cod,
tuna) and “cartilaginous fish” (e.g., sharks). All bony fish share the protein
parvalbumin, which is known to trigger allergic reactions. For this reason
many people with seafood allergies are allergic to many different kinds of
fish. It is not known whether cartilaginous fish also have parvalbumin.
However, some people with fish allergies will be allergic to fish in both
groups. Cod is the most widely reported fish allergy.

Crustaceans. A large group that includes crabs, lobsters and shrimp. It is
common for individuals allergic to this kind of seafood to react to all forms
of crustaceans (and often mollusks as well).

Mollusks. A broad group that includes mussels, oysters and clams. Most
people who are sensitive to one type of mollusk are sensitive to them all, as
well as all types of crustaceans. The type of protein shared by both
crustaceans and mollusks is called tropomyosin
An allergic reaction is triggered in sensitive individuals when a seafood protein
makes its way into the body. This process, called an allergic cascade, can begin
when the patient:


Eats seafood proteins
Inhales proteins (e.g., from cooking seafood)

Absorbs proteins through the skin (e.g., while
handling seafood)
The allergic cascade is triggered when the immune
system overreacts to a seafood protein, believing it is
a dangerous substance. To combat the protein, the
immune system releases IgE antibodies into the
bloodstream. These antibodies interact with body cells
(mast cells and basophils) to trigger the release
of histamines and other chemicals into the blood.
It is the histamines and other chemicals that stimulate allergy symptoms. By
causing blood vessels to swell and individual cells to leak fluid, histamines
produce allergy symptoms such as itchiness, rash, hives, stomach cramps,
nausea and respiratory problems. Individuals who are sensitive to allergic seafood
reactions can go into life–
In some cases, a reaction to fish may be caused by a toxin the fish ingested. Such
a toxin may cause an allergic reaction, or it may cause food poisoning (which can
be mistaken for an allergic reaction). Bacteria or viruses within seafood may also
cause allergy–like symptoms – especially in areas with polluted coastal waters.
Raw fish tends to be the most dangerous form of seafood, provoking the
strongest reactions in sensitive people. Cooking fish has proven effective at
reducing the ability of the proteins found in fish to start an allergic reaction.
Thoroughly cooking fish can make it possible for some mildly–allergic individuals
to consume fish without a reaction. However, only a physician can determine
whether an allergic person can safely consume any type of seafood.
Seafood allergies tend to be more common in countries where seafood is a dietary
staple and consumed regularly. Also, susceptibility to seafood allergies is believed
to be genetic. Individuals with a personal or family history of any type of allergy
(e.g., allergic rhinitis or eczema) are more likely to have a seafood allergy.
Potential Sources of seafood allergies
People with seafood allergies must also be careful of the many types of foods that
contain fish or shellfish products. Even a trace amount of seafood protein can
trigger an allergic reaction. Some common products that frequently contain
seafood components are:

Worcestershire sauce. Contains fish (anchovies).

Caesar salad. Often contains fish (anchovies) either on the salad or in the
dressing.

Caviar. Made of fish eggs.

Marinara sauce. Sometimes contains fish (anchovies).

Roe. Unfertilized fish eggs.

Surimi (a type of imitation crab popular in some Asian restaurants).
Contains fish proteins for added flavoring.

Hot dogs, bologna and ham. Can contain fish flavoring (surimi).

Pizza toppings. Sometimes contains fish (anchovies).

Caponata (a Sicilian relish). Can contain fish (anchovies).

Coffee and wine. Fish skin is used to clarify some of these drinks.

Pet fish food. This dried substance is made of brine shrimp and other
seafood. It can easily become airborne and, if inhaled, may trigger
symptoms in some people with seafood allergies.
Cooking seafood with other types of food often leads to seafood protein
contamination of normally safe foods. For instance, restaurants use vats of oil to
fry their foods – often using the same vats to fry shrimp, chicken, French fries and
more. Grills and spatulas at restaurants can also become contaminated if they are
not cleaned properly after cooking seafood.
Some individuals can be sensitive to the airborne fumes produced by cooking fish.
These people can also have an allergic reaction triggered by simply walking
through a fish market. Individuals who are this sensitive should be very careful
about dining in restaurants or unfamiliar places. Sensitive individuals can also
receive an allergic reaction from skin contact with fish and should avoid handling
seafood.
For more information please refer to www.allergyhealthonline.com
September 2005