What Are the Symptoms of a Shellfish Allergy in Kids?

Dad serving pasta with mussels to child

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Your toddler comes to you in tears, yet unable to verbally express what's wrong. You see them scratching, so you lift their shirt and discover small red welts spreading over their skin.

Concerned about what looks like an allergic reaction, you mentally tally up everything they have eaten that day. Oatmeal, berries, a glass of milk, grapes...and then you remember. They gobbled up the crab cakes you made for lunch that day. Seems like they could be reacting to shellfish, but you aren't sure what to do next.

Shellfish is a common allergen. It has the potential to develop at any time, so it's important to know the signs of a reaction and how to treat it, including when to seek emergency care.

What Is a Shellfish Allergy?

The types of animals that we call shellfish fall under several different categories, most notably crustaceans and mollusks. Crustaceans, such as lobster or crab, have segmented bodies, antennae and jointed limbs. Mollusks on the other hand, have soft, unsegmented bodies. Oysters and mussels are mollusks.

It is possible to be allergic to only certain types of shellfish. "In general, a food allergy happens when our body reacts to a protein in a certain food," explains Mona Amin, MD, a board-certified pediatrician and owner of Peds Doc Talk. Most commonly, people are allergic to crustaceans, but might be able to eat mollusks.

Despite the name, shellfish are not actually fish, and shellfish allergy is completely separate from fish allergy.

When Do Shellfish Allergies Develop?

You might see an allergic reaction the first time your baby tries shellfish, or they might be totally fine and have a reaction when they are older. For this reason, it's important to be aware of the signs of an allergy, particularly during the years that your child may have a hard time articulating the problem.

"Although shellfish allergies are more common in adults, they can affect children and babies of any age," notes Amanda Stovall, MD, a board certified pediatrician at Springfield Clinic in Central Illinois. "People can develop allergies to shellfish even if they have eaten them in the past without any problems."

Signs and Symptoms of a Shellfish Allergy

If your child is having an allergic reaction to shellfish, they might complain that their mouth is itchy or "hairy". They may have hives on their body. But you might also see symptoms such as sneezing, itchy eyes, stomach pain, or diarrhea. Shellfish allergy can present in a variety of ways.

In the case of a severe reaction, anaphylactic shock may occur. This is a life-threatening emergency. Symptoms leading up to anaphylactic shock include swelling of the face, mouth, or throat, shortness of breath, or difficultly speaking or swallowing.

"Anaphylaxis is a total-body immune response to the allergen, such as shellfish, meaning people typically will have more than one symptom," notes Dr. Stovall. "Signs of a serious reaction to shellfish can begin a few minutes up to a few hours after ingestion."

How Is a Shellfish Allergic Reaction Treated?

Mild allergic reactions can be treated with over-the-counter antihistamines. Be sure that any medicine you use is appropriate for your child's age and weight, and always get the okay from your child's pediatrician or healthcare provider.

An anaphylactic reaction to shellfish is treated with epinephrine, often administered with an EpiPen. "If your child has a known allergy that causes anaphylaxis, it is important to always have an EpiPen available," notes Dr. Stovall.

When to Seek Medical Attention

If you notice a potential mild reaction for the first time, it is always a good idea to call your child's pediatrician or healthcare provider. They may advise you on which medications to use, or they may want to see your child and conduct an allergy test to confirm the allergy. "If your child is having two or more mild symptoms within an hour of a potential allergen, it’s important to also seek medical attention as well," notes Dr. Amin.

If your child has difficulty breathing or swallowing, has swelling of the face or throat, or becomes dizzy or faints, dial 911 for emergency assistance. If you have an EpiPen, use it and also call for help. If someone else is with you, have them call while you administer the EpiPen. Otherwise, administer it yourself, and call immediately after.

Ongoing Allergy Management

Food allergies do not have a cure. However, letting your baby try common allergens like shellfish may help reduce the chance of an allergy developing. "To be proactive, if you still have a little one who hasn’t started solids or is about to start solids, consider introducing the top...allergenic foods 'early and often,'" says Dr. Amin. The U.S. Food and Drug Administration cites the top allergenic foods as milk, eggs, fish, Crustacean shellfish, tree nuts, peanuts, wheat, and soybeans.

The best thing you can do is prevent reactions by avoiding the allergen. Teach your little one to ask before they eat food that is offered to them, starting at a young age. When they get older, they should know if they cannot eat certain foods.

Your child's school staff should be aware of their allergy. If an EpiPen is necessary, their teacher should have one labeled with your child's name.

The teacher or adult that cares for your child needs to be able to recognize when your child is having a reaction, and know how to use the EpiPen. "Older children should carry an EpiPen with them in a purse or backpack and be taught how to use it in case of emergency when their parents or teachers are not around," says Dr. Stovall.

A Word from Verywell

Shellfish allergy is one of the most common allergies. It is possible to develop at any time, even if your child has eaten shellfish before without any problems. Some children may be allergic to all shellfish, while others may only react to crustaceans, but not mollusks.

Sign of an allergic reaction may include an itchy mouth, hives, stomach ache, or sneezing. Mild allergic reactions can be treated with antihistamines, while severe reactions require an EpiPen. If your child has swelling of the face or throat, or any trouble breathing or swallowing, call for emergency help. Administer an EpiPen at this point if you have one.

Food allergies cannot be cured, and avoiding the allergen is the best way to prevent a reaction. When it comes to allergies, it's always okay to seek medical help if you are unsure of the severity.

If you have any questions or concerns about your child's potential food allergies, reach out to your your child's pediatrician or healthcare provider.

4 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American College of Allergy, Asthma, and Immunology. Shellfish.

  2. Food Allergy Research and Education. What Is Shellfish Allergy?

  3. National Health Institute. Shellfish Allergy.

  4. U.S. Food and Drug Administration. Food Allergies.