Food Allergy

Deep Dive: Everything You Need to Know About Fish and Shellfish Allergies

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Trust20 Contributors • 13 minute read

Whether you work in a five-star restaurant or a college dining hall, you know that serving up fish and shellfish is a great way to make a splash. Experimenting with seafood recipes is incredibly fun, and chances are, these are some of the most popular dishes on your menu.

However, they can also be some of the most dangerous, as fish and shellfish allergies account for some of the most severe allergic reactions among vulnerable people, with symptoms ranging from hives and swelling to life-threatening anaphylaxis.

As a foodservice professional, it’s vital you understand the ins and outs of fish and shellfish allergies to help protect your customers. In this post, we’ll explore the topic in depth so you can confidently navigate these allergies.

Here’s what we’ll cover:

What is a Fish and Shellfish Allergy?

Identifying and Addressing a Fish or Shellfish Allergic Reaction

How to Safely Serve Customers With Fish and Shellfish Allergies

Other Fish-Related Hazards to Be Aware Of

What is a Fish and Shellfish Allergy?

Did you know that about 2% of our country’s population (around six million people) is allergic to shellfish?1 That accounts for a sizable chunk of the potential customers who walk through your doors every day!

On top of that, a whopping 60% of people who are allergic to shellfish experienced their first symptoms in adulthood, not childhood, a fact that makes this allergy quite different from other common food allergies (like those to peanuts or tree nuts).1

A customer could very realistically walk into your establishment and order scallops for the first time without realizing they’re deathly allergic to them. Therefore, you need to educate yourself not only on how to avoid cross-contamination but also on how to address reactions when they do happen.

But before we can do that, we need to start by explaining what a fish or shellfish allergy is. To do that, let's differentiate between fish and shellfish allergies.

A fish allergy is an immune response to the proteins found in the flesh of finned fish like salmon, tuna, or halibut. On the other hand, a shellfish allergy is a reaction to the proteins found in shellfish such as shrimp, crab, or lobster. In either case, these allergies can range from mild to severe, so it's critical to take them seriously.

So, what different types of shellfish can people be allergic to? Shrimp is the most commonly reported allergen, followed closely by crab and lobster. Other shellfish that people may have allergic reactions to include oysters, clams, and scallops. 

Some people may be allergic to all types of shellfish, while others may only react to one or two. Unfortunately, even a small amount of shellfish can trigger a severe allergic reaction, so cross-contamination must be avoided at all costs.

It's also worth noting that shellfish allergies are often a lifelong condition, while finned fish allergies may be outgrown over time.1 However, in both cases, it's best to entirely avoid the allergen for the person’s own safety. 

Identifying and Addressing a Fish or Shellfish Allergic Reaction

As we mentioned earlier, foodservice professionals need to know how to prevent reactions and what to do if they arise–these can often happen without warning or the customer's knowledge that they’re allergic in the first place.

Symptoms of a reaction usually occur within minutes to an hour after ingesting the allergen and can include:

  • Hives, itching, and redness of the skin

  • Swelling of the face, lips, tongue, and throat

  • Trouble breathing, wheezing, and coughing

  • Nauseous, abdominal pain, and vomiting

  • Dizziness, confusion, and fainting.2

In severe cases, anaphylaxis–a potentially life-threatening allergic reaction that can cause a sudden drop in blood pressure, loss of consciousness, and shock–can occur.

If someone is experiencing the symptoms mentioned above, you must act quickly. Here are some steps to take:

  • Call emergency services immediately and describe the situation. Time is of the essence with anaphylaxis, and quick action can save lives.

  • If the person has an EpiPen, they should use it right away. EpiPens are injection devices containing epinephrine, which can counteract the allergic reaction.

  • Stay with the person until emergency services arrive. Keep them calm and reassure them that help is on the way.

It’s also important to note that reactions, particularly anaphylaxis, can start out mild and then progress. Because of this, if a customer has a known food allergy and starts having symptoms of a reaction, you should act immediately and assume the worst could happen. 

How to Safely Serve Customers With Fish and Shellfish Allergies

We now know that allergies can be a serious issue, especially when it comes to fish and shellfish. With that in mind, here are some tips to keep everybody safe. 

1. Read Labels Carefully

Take a second to pause before assuming that anything that isn’t fish is safe for someone with a fish allergy.

The problem is that fish and seafood-based ingredients are extensively used in pre-packaged processed foods, sauces, dressings, and condiments that you least expect to add that piquant "umami" flavor. These can include fish stock, fish sauce, caviar, and even Worcestershire sauce.3

So, if your “allergen-free” menu boasts dishes like Caesar salad dressing or cocktail sauce, think again! These products also contain anchovies, which can be a lethal trigger for those with seafood allergies.

Unfortunately, it’s not just food products that you need to be mindful of either. While you likely won’t deal with these too much in the kitchen, know that things like fish oil supplements are also problematic. Essentially, anything with even a trace amount of fish or shellfish can be an issue for customers with allergies, so read labels for absolutely everything with an eagle eye.

2. Pay Special Attention to Prepared Foods

Again, paying particular attention to prepared foods is crucial. Even seemingly innocent foods like Worcestershire sauce, Caesar salad, imitation crab products, stock, and barbecue sauce can contain fish ingredients. Bouillabaisse, caponata, and other dishes also often have fish in them, making it difficult for customers with allergies to find safe options.

Multicultural cuisines, particularly African, Chinese, Thai, Indonesian, and Vietnamese, also contain hidden sources of fish. Did you know that kimchi, a popular Korean dish, is traditionally made with fish sauce? That is just one example of how even seemingly fish-free dishes can have hidden ingredients that can cause allergies.

3. Don’t Forget About Gelatin

Another sneaky troublemaker? Gelatin.

Gelatin isn’t on the list of the most common allergens, but it could potentially be a trigger for someone with allergies. You see, gelatin is made from fish skin and bones–which means it could also affect customers with sensitivities.

The good news is it’s not as common for people to be as reactive to gelatin as they might be to an actual fish filet or lobster claw. It doesn’t actually contain the fish protein that triggers most allergic responses.

However, it’s certainly not unheard of. Keep this ingredient in mind when preparing, serving, and marketing your dishes.

4. Mind Your Suppliers

Even if you do everything right, problems with allergies can arise even before the foods enter your front door.

You might be surprised to know that some suppliers are not entirely honest about their products. Oceana, a non-profit ocean conservation group, completed a study that found that many types of fish look alike once filleted.4 Dishonest suppliers may substitute cheap fish for more expensive types of fish, putting your customers' health at risk.

As a result, you may unknowingly be serving dishes that are not at all what you intended.

So, how do you ensure you receive what you're paying for? The first step is to establish a trustworthy relationship with your supplier.

Check their reviews, talk to other foodservice businesses, and conduct a background check. Then, have a thorough conversation with your supplier about their inventory and the sources of their products. 

5. Have a Clear, Thorough Conversation with the Customer

Keeping your customers with allergies safe and well-taken care of always starts with a clear, thorough conversation with the customer.

Translation: ask if they have any allergies. If they do, and if they’re to fish or shellfish, ask what type of fish they’re allergic to. About half of all people who are allergic to one type of fish are also allergic to other fish, though, so even if your dish doesn’t contain the exact type of fish that the customer is allergic to, it's still important to know if they're allergic to any other types of fish.5

But don't just stop there–keep the conversation going! Ask the customer what symptoms they experience when they have an allergic reaction to seafood. That will help you recognize the signs of an allergic reaction and take the necessary steps to ensure their safety.

6. Make Sure Steam Doesn’t Reach Dining Areas

Another factor to remember when dealing with customers with allergies is the proximity of your dining area to the kitchen.

When fish is cooked, its steam can contain tiny particles of fish protein. Even a small exposure to these particles can cause a severe reaction for someone with a fish or shellfish allergy. And that’s something no one wants to see happen in their establishment.

So, what can you do to prevent this from happening? First, separate the area where fish is being cooked from the dining area. That will help ensure that the steam doesn’t reach your customers. If this is not possible, consider using a high-quality exhaust system to capture as much of the steam as possible.

Another option is to use alternative cooking methods, such as grilling or broiling, which produce less steam than methods like boiling or steaming. But if you do need to use these methods, be sure to take extra care to keep the steam under control.

7. Know the Difference Between Fish Allergy and Carrageenan or Iodine Allergies

Something else that comes up often when dealing with fish allergies is concerns about carrageenan or iodine.

Remember, a fish allergy is triggered by the proteins found in fish like salmon, tuna, and cod. Carrageenan, on the other hand, is a commonly used food ingredient extracted from red seaweed. It is often used as a thickener and stabilizer in food products, and it can also cause allergic reactions in some people–but it is an entirely separate allergy from a fish or shellfish allergy.

Similarly, iodine allergy is caused by a reaction to iodine, which is sometimes used in seafood processing and medical procedures. Again, this is an entirely different allergy. 

8. Prepare Dishes That Contain Fish or Shellfish in a Separate Section of the Kitchen

Consider designating a section of the kitchen as an allergen-free prep spot. Although this might seem like a hassle, it's a small change that can make a big difference to customers with allergies.

Creating a separate section of the kitchen to prepare your seafood dishes helps you avoid cross-contamination, a primary cause of allergic reactions. That means separate cutting boards and utensils when possible (color-coding is a good way to keep these separate).

9. Use a Different Fryer and Grill for Fish or Shellfish Products

When you cook fish or shellfish in the same fryer or grill as other foods, there's a chance that cross-contamination could occur. Even a small amount of fish or shellfish can cause a severe reaction for those with allergies, which is why it's crucial to take steps to prevent any cross-contact.

By using separate fryers and grills for fish and shellfish, you can prevent cross-contamination and ensure that your customers with allergies can safely enjoy their meals.

For example, you could designate one grill for fish, one for burgers, and other non-fish items, like french fries or onion rings.

10. Inform Customers of Substitution Options 

Always inform your customers about their options. For example, instead of serving a seafood paella, consider offering a chicken and vegetable alternative. Or, if a customer is allergic to shrimp, suggest a dish with scallops instead.

You don't have to stop at just seafood, either. Offering substitution options for all dietary restrictions, such as vegetarian or gluten-free, shows that you care about your customers' needs and can also increase your customer base and boost revenue.

11. Make Sure Your Staff Wears Gloves and Separate, Clean Cookware for Allergic Customers

Make sure your staff wears gloves when handling food to prevent cross-contamination. Emphasize the importance of using separate, clean cookware. Don't use the same tongs, spatulas, or pans for allergic and non-allergic customers. Having some extra cookware can come in handy. Invest in separate pots and pans, and you'll be good to go.

It's also wise to have a system for identifying allergen-free orders. One popular method is to place a sticker on the to-go containers, which labels them as containing allergy-safe food. Depending on the allergy, you could also use a system of different-colored plates or bowls. It's all about finding a method that works for you and your staff.

12. Do Everything in Your Power to Eliminate Cross-Contamination

Cross-contamination is a huge concern when it comes to seafood allergies. Even a trace amount of fish or shellfish can cause a severe reaction in some people. Don’t risk it.

Make sure everything is sanitized, labeled, and kept separate. If an allergen accidentally winds up on a customer’s plate when it shouldn’t be there, don’t just remove it from the plate and call it good to go. Even invisible, minuscule amounts of an allergen can make people incredibly sick.

13. Label Everything on the Menu Clearly

Labeling is key. Make sure everything on your menu is clearly labeled with its ingredients. That way, customers will know precisely what they can and cannot eat. This small step can make a huge difference.

14. Incorporate Signage

One of the most effective ways to proactively address fish and shellfish allergies is by incorporating signage throughout your establishment. That can help ensure that everyone on your team is aware of the risks and provide clear guidance to customers.

For example, consider adding signs to your front entrance and host stand that clearly indicate that you serve fish and shellfish. That can help customers make informed dining decisions before stepping inside your establishment.

Other Fish-Related Hazards to Be Aware Of

These can affect anybody, not just people with allergies, but are important to prevent in foodservice.

When it comes to fish and shellfish, there is, unfortunately, more that you need to be aware of in terms of safety instead of just run-of-the-mill allergies. Fish allergies are widespread, but there are other fish-related hazards unique to fish and seafood that you need to be aware of. 


One of the most common fish-related hazards is scombroid poisoning.6 This occurs when fish that have not been properly stored start to break down, leading to the production of histamines. Symptoms of scombroid include flushing, sweating, headaches, and tingling around the mouth. 

While not life-threatening, scombroid can be very unpleasant. To prevent it, fish should be chilled to below 41°F as soon as possible after being caught. You should also check the temperature regularly and discard any fish above this temperature.

It's important to note that scombroid is not an allergic reaction. Allergies are caused by an immune system's response to a particular protein. In contrast, scombroid poisoning is caused by a buildup of histamines in the body. Knowing the difference between the two is critical to providing the right treatment.

Anisakis Simplex

Another fish-related hazard to be aware of is Anisakis simplex.6 This parasitic worm found in fish and seafood can cause an infection or allergy. Infection is caused by consuming Anisakis larvae, resulting in severe stomach pain and vomiting. 

Anisakis allergy is caused by an immune system response to the worm, which can cause breathing difficulties, hives, and even anaphylaxis (a life-threatening allergic reaction). 

You should always freeze fish at -4°F for at least seven days before consumption to prevent Anisakis infections.

Ciguatera Poisoning

Ciguatera poisoning is another fish-related hazard that can occur when consuming certain types of reef fish. This kind of illness happens when the fish consume toxic algae, which accumulate in the flesh of the fish.6

Its symptoms include nausea, vomiting, and tingling in the fingers and toes. While not fatal, it can be uncomfortable for several days. Again, you should buy fish only from reputable suppliers and avoid consuming large predatory fish like barracuda, which are commonly associated with ciguatera poisoning.

Metabisulfite Reactions

Finally, metabisulfite reactions are a risk factor for those sensitive to sulfites.6 This can occur when fish are treated with metabisulfite as a preservative. Symptoms include hives, itching, and difficulty breathing. To prevent metabisulfite reactions, check the labels of any fish products for sulfites and avoid using them if possible.

Final Thoughts

Addressing fish and shellfish allergies is paramount for anybody working in foodservice. Ignoring this issue can lead to disastrous consequences for customers and business owners alike.

At Trust20, we understand the importance of maintaining a culture of food safety throughout your establishment. That’s why we offer a variety of products to help your business thrive and overcome any challenges related to food allergies.

Check them out today–the right training will ensure everything goes swimmingly!

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  1. Cleveland Clinic: Shellfish Allergy: Causes, Symptoms, Diagnosis & Treatment

  2. FDA: Food Allergies: What You Need to Know

  3. American College of Allergy Asthma and Immunology: Fish Allergy | Causes, Symptoms & Treatment

  4. Oceana: Oceana Study Reveals Seafood Fraud Nationwide

  5. FARE: Fish

  6. Australian Society of Clinical Immunology and Allergy: Allergic and toxic reactions to seafood