Seafood Allergies (Fish and Shellfish) Causes, Treatment, Prevention

Seafood allergies are among the more common food allergies. It affects between 2% to 3% of the American population although this figure may be higher as mild seafood allergies are not always reported. Not all seafood allergies are mild and some can even be life-threatening. With a severe type of allergic reaction known as anaphylaxis, a person may die if there is no access to immediate medical attention. In milder cases though a seafood allergy may cause itching skin and eyes or even slightly heavy breathing.

What is a seafood allergy?

A seafood allergy is an immune reaction triggered by the presence of seafood (certain fish and shellfish) usually when it is eaten. People who have an allergy will therefore experience symptoms when they consume the trigger food (allergen). Sometimes this allergic reaction will resolve on its own within a few hours but at other times medical attention is necessary to control and stop the reaction. Overall seafood allergies and specifically shellfish allergies are more common among adults than children.

Unlike other food allergies related to wheat, dairy, egg yolk, peanuts and soy, a seafood allergy does not always start in childhood. It can arise in adulthood with no previous history of a seafood allergy and the reason for this late onset is not always clear. Most of the time the allergic reaction is initiated when seafood is eaten but sometimes even touching or smelling seafood can cause it. Salmon, tuna, cod and catfish are the commonly reported fish species to trigger seafood allergies. Shrimp, crab, lobster, scallops, oysters and clams are the main problem shellfish but even octopus and squid can be a trigger.

Causes of Seafood Allergy

As with an allergy, the trigger food is not the actual cause. In fact the exact cause of an allergy is not understood although it may be related to genetic factors. What is known that the triggers (allergens) initiate an immune response when it enters the body. Normally the immune system acts against toxic compounds and invading pathogens like bacteria and virus. In this way it protects the body against harm by neutralizing the threat as fast and as effectively as possible.

However, with an allergy an otherwise harmless substance may trigger this defensive action by the immune system. In this case the allergen is seafood like certain fish and shellfish which are commonly eaten foods. It does not pose a threat to the body in the same way as bacteria and viruses but the immune system reacts in a similar way. Inflammation is the body’s way of preventing tissue damage and it is initiated by the action of the immune system in an allergic reaction.

When this inflammation is isolated to one area, like the skin or respiratory tract then localized symptoms may occur such as itching or wheezing, respectively. However, it is also possible for an allergic reaction to be systemic meaning that the inflammation may be widespread throughout may parts of the body or even the entire body. The skin, respiratory system and gastrointestinal system are usually the most affected in a food allergy so symptoms are often localized to these organs and systems.

It is important to note that seafood allergies can arise suddenly even without a previous history of allergies to fish or shellfish. Sometimes the first exposure to a seafood that was never eaten earlier in life may not present with any reaction. Many people then believe that they do not have an allergy to that specific seafood but successive exposure will the trigger the allergic reaction.

Signs and Symptoms

Mild to moderate allergic reactions may present with one or more of the following symptoms which appear within minutes to hours after eating seafood. The severity of symptoms does not depend on the quantity of seafood eaten. Even small quantities can trigger a reaction.

  • Swelling of the lips, tongue, throat or face. Sometimes other parts of the body may become swollen.
  • Tingling of the lips, tongue or the entire mouth.
  • Itchy red skin.
  • Difficulty breathing.
  • Stuffed nose.
  • Wheezing.
  • Nausea and sometimes vomiting.
  • Abdominal pain.
  • Diarrhea.
  • Lightheadedness and dizziness.
  • Fainting (uncommon).

Severe allergic reactions are known as anaphylaxis or anaphylactic shock. It is a very dangerous type of allergic reaction that can lead to death. Symptoms of anaphylaxis may be similar to milder reactions at the outset but progressively worsens. It can start within seconds of putting seafood into the mouth. The symptoms of anaphylaxis include:

  • Extreme swelling of the throat where a person feels a lump-like sensation in the throat and experiences difficulty breathing or talking.
  • Difficulty breathing usually with gasping for air.
  • Rapid heart rate and low blood pressure.
  • Lightheadedness and dizziness often progresses to loss of consciousness.

Treatment and Prevention

The treatment for a seafood allergy largely depends on the severity of the allergic reaction. Very mild reactions may not even require medical treatment and eases over a few hours or days on its own. However, most people who have even mild allergies find the symptoms troublesome and seek treatment. Mild allergies can be treated with antihistamines and related allergy medication. Severe reactions will require the injection of epinephrine (adrenalin). People who are at risk of anaphylaxis need to carry epinephrine injections at all times.

Seafood allergies should be prevented by avoiding trigger fish and shellfish. However, it is not always simple to avoid these triggers as there may be fish protein in a number of different foods. It is therefore important to thoroughly read food labels and avoid packaged or processed foods from questionable suppliers with without proper labeling. Also be cautious when eating at a restaurant or fast food outlet as there may be cross-contamination of foods with seafood even if the meal being eaten does not contain seafood.

WARNING: Never delay seeking medical treatment for a seafood allergy if it occurs for the first time. You cannot be sure that it will be a mild reaction. Anaphylaxis can be deadly within minutes. Even people who previously suffered with mild reactions can develop more serious reactions in time. There is no certainty as to when these severe reactions may arise.

Please note that any information or feedback on this website is not intended to replace a consultation with a health care professional and will not constitute a medical diagnosis. By using this website and the comment service you agree to abide by the comment terms and conditions as outlined on this page

Ask a Doctor Online Now!