Suddenly allergic to shellfish? Here’s how to cope.

Unlike most food allergies that develop during childhood, a shellfish allergy typically emerges during the teenage or adult years. You may have eaten shellfish without any issues for years and then suddenly experience allergic reactions after consuming crustaceans or molluscs.

Before we share with you the ways to cope with shellfish allergy, let us first identify which foods qualify as shellfish and which symptoms point to a shellfish allergic reaction.

What causes shellfish allergy?

Shellfish are classified as either crustaceans or molluscs. Below are examples of each category:


  • crab
  • crayfish
  • lobster
  • prawn
  • shrimp
  • yabbies


  • clams
  • cuttlefish
  • mussels
  • octopus
  • oysters
  • scallops
  • snails
  • squid

A protein called tropomyosin found in crustaceans and molluscs triggers a reaction from the immune system of individuals who are allergic to shellfish. This allergic response involves the release of a chemical known as histamine to fight off what your body believes to be a harmful foreign substance that has entered your system. This chemical triggers the symptoms of your shellfish allergy.

What are the symptoms of shellfish allergy?

Shellfish allergy symptoms can range from mild to life-threatening, but they tend to be severe in most cases. While signs of an allergic reaction to shellfish may take some time to appear, they may manifest right away in some cases.

Common symptoms of a shellfish allergy include:

  • Tingling sensation in the throat and mouth
  • Swelling of the lips, tongue, face, ears, throat, hands or fingers
  • Itchy skin, rashes, hives (urticaria) or eczema (atopic dermatitis)
  • Stomach aches
  • Diarrhoea
  • Nausea and/or vomiting

 Anaphylaxis or severe allergic reactions may also occur, such as:

  • Throat congestion, wheezing and difficulty breathing
  • Dizziness or lightheadedness that can lead to fainting
  • Accelerated heart rate
  • Shock caused by a drastic drop in blood pressure 

Although allergic reactions to shellfish occur post-ingestion of the offending food, your symptoms can also be triggered after being in contact with shellfish or inhaling steam produced from cooking or processing them.

3As to cope with a sudden shellfish allergy

Before you can properly address the symptoms of your shellfish allergy, you need to get an accurate diagnosis of your condition first. Seek the help of a professional medical practitioner, specifically an allergist, to confirm what types of shellfish you are allergic to.

You will be more effective in managing your symptoms once the culprit of your shellfish allergy has been determined. Below are ways to manage your allergic reactions from crustaceans and/or molluscs:


The most effective way to prevent your symptoms from manifesting is by avoiding shellfish altogether. This means you have to make it a habit to read food labels and refrain from consuming foods and products with ingredients derived from either crustaceans or molluscs. Food manufacturers and suppliers are required to declare on their labels whether their goods contain any of the items included in the list of food allergens (e.g., egg, fish, milk, peanuts, shellfish, soybeans, tree nuts and wheat) so you should be able to tell right away if it’s safe for you or not.

When you’re eating at a friend’s house, dining in a restaurant or any place where you don’t know how the food is prepared, make sure you inform the host or your serving attendant that you are allergic to shellfish.


You may take antihistamines if you only experience mild symptoms after eating shellfish. Antihistamine is a drug or substance that suppresses the effects of histamine that is released when your body comes in contact with allergens. Just remember that antihistamines are not effective for severe allergic reactions. For your safety, consult your doctor before taking any medication for your allergy.


Anaphylaxis is more common with shellfish allergies than with any other type of food allergy. For this reason, many individuals who are allergic to shellfish carry an auto-injector that allows them to self-administer a dose of epinephrine in case they experience a severe allergic reaction. Epinephrine is a medication that helps relax the muscles lining the airways to allow you to breathe normally and reduce swelling and itching. Getting a shot of epinephrine is the first course of action that needs to be taken in the event of an anaphylactic reaction.

Take note that you need to see a doctor immediately even after receiving a shot of epinephrine to ensure that a second wave of attack will be managed properly.

Living with a shellfish allergy

Being allergic to shellfish all of a sudden can be difficult and disappointing. Not only will you miss out on delicious seafoods, but you will also run the risk of suffering from a fatal allergic reaction. Avoiding crustaceans and molluscs completely is one of the most effective ways to prevent your symptoms from manifesting in the first place. If your symptoms are mild, your doctor may prescribe you antihistamines so you can still enjoy shellfish minus the allergic reactions. It will also be better if you can carry with you an auto-injector like Epipen at all times.

We can help you cope with your shellfish allergy

Our accredited dietitians and nutritionists can help you manage the symptoms of your shellfish allergy through personalised programs, practical methods, and proven techniques. Call us now at (07) 3071-7405 to book an appointment with one of our accredited dietitians and nutritionists.