What You Need to Know About Pizza Allergens

A survey conducted by CiCi’s Pizza, reported in the New York Daily News, revealed that the average American will eat more than 6,000 slices of pizza in their lifetime. There’s no question that many of us are fond of pizza, but allergy-triggering substances (allergens) in pizza can keep some people from enjoying it.

The most common allergens in pizza are casein, tomato, and yeast. Allergic reactions to them can cause symptoms ranging from stomach upset to trouble breathing and even death.

This article will explain how these ingredients cause allergies, what symptoms to watch out for, when a reaction requires medical care, and how to make substitutions that will allow you to enjoy pizza safely.

Homemade pizza on a wooden kitchen table
Rekha Garton / Getty Images

Common Pizza Allergens

Casein Allergy

Casein is the main protein found in dairy products like cheese and milk. It's a good source of essential amino acids needed for our bodies to function.

With a casein allergy (also referred to as a milk allergy), the immune system mistakenly thinks that casein is a threat to the body and works to fight it off. This can trigger unpleasant gastrointestinal symptoms, and sometimes even skin or respiratory symptoms.

Casein allergy is one of the more common food allergies, especially in infants and young children. Nonetheless, research shows that up to 75% of children outgrow their milk allergy.

It’s important to note that a casein allergy differs from lactose intolerance. Lactose intolerance is when the body cannot digest lactose, the primary sugar found in milk and dairy products. Lactose intolerance occurs when the body does not produce enough of the enzyme lactase, which is needed to digest lactose.

Tomato Allergy

Pizza sauce is typically made with fresh tomatoes or tomato paste. Having a true tomato allergy is rare, but it’s possible that certain chemicals and proteins found in tomatoes may cause adverse reactions in some people.

For example, tomatoes are one of the nightshade vegetables, a family of flowering plants that contain chemical compounds known as alkaloids. Although it's rare, those who do have a tomato allergy may be allergic to alkaloids or have some sort of intolerance towards them.

In addition, tomatoes contain high amounts of histamine, a chemical naturally produced in our bodies. Histamine supports the immune system by acting as a chemical messenger between cells. It is released when the body is affected by a foreign invader or allergen and leads to responses like increased blood flow and inflammation.

Some people have what is known as histamine intolerance. With this condition, the body typically has problems producing enzymes responsible for breaking down histamine, notably the enzyme diamine oxidase. Because of this, histamine can build up in the body and cause symptoms, especially when foods containing high amounts of it are consumed.

However, a more common reaction to tomatoes is what's known as oral allergy syndrome (OAS), which causes symptoms such as itching of the mouth and lips. OAS is the result of an allergy to certain types of pollen. For instance, some proteins found in grass pollen are similar to proteins in tomatoes, so people who are allergic to grass may have a reaction to tomatoes.

Yeast Allergy

Pizza dough usually contains yeast. There are differences in opinion among experts about whether it is possible to have a true yeast allergy.

Some experts believe that people can be allergic to specific proteins found in yeast, but others argue that there is a lack of scientific research in this area to support this claim.

Moreover, it’s also possible that those believed to be allergic to yeast may have an intolerance or sensitivity to it instead, in which their body is unable to digest it adequately, causing adverse reactions.

Signs and Symptoms of a Food Allergy

Symptoms of a food allergy can differ from person to person, but common ones include:

  • Red, watery, or itchy eyes
  • Itchy throat
  • Hives
  • Swelling of the skin and rashes (e.g., eczema)
  • Digestive problems such as upset stomach and diarrhea

A more serious symptom of a food allergy is known as anaphylaxis. Anaphylaxis is a severe type of allergic reaction that can progress to anaphylactic shock and even death.

Anaphylaxis symptoms include swelling of the face, throat, or other parts of the body, as well as wheezing, confusion, weakness, shortness of breath, and loss of consciousness.

Management and Prevention

As pizza commonly contains casein, tomato, and yeast, it’s important to know that there are substitutes for ingredients that include these allergens.

If you have a casein allergy, opt for non-dairy cheese options such as soy cheese. Ordering pizza without cheese but with your other favorite toppings is also an option.

For a tomato allergy, opt for tomato sauce-free types of pizza, like white pizza, salad pizza, or barbecue chicken pizza. If you cannot have yeast, try looking for restaurants or stores that serve pizza made with yeast-free dough. You can even make your own yeast-free pizza by substituting baking soda for yeast when making pizza dough.

Sometimes, especially with processed foods, allergens may be included as preservatives or flavorings. Be sure to read food labels to make sure a food doesn't contain any ingredients that are problematic for you, and don't be afraid to ask questions about menu items at restaurants.

When it comes to allergies, you should also be aware of the potential risk of cross-contamination. When ordering pizza from a restaurant, make them aware of your allergies and ask them about how the pizza you are interested in is made.

If the kitchen stores your chosen toppings close to other ingredients that contain allergens, there is a risk of exposure. And if cooks handle ingredients with allergens, then handle your toppings without first changing their gloves, there is also a risk.

When to Seek Treatment for an Allergic Reaction

Over-the-counter antihistamines such as Benadryl can treat mild allergic reactions with symptoms such as itchy eyes and nasal congestion. If such symptoms are too bothersome or don't get better, talk with your doctor to discuss the next steps for treatment.

Symptoms like low blood pressure, weak pulse, swollen lips, increased heart rate, difficulty breathing, and sudden weakness are signs of anaphylaxis and require emergency treatment. Use an EpiPen, if one is available, and get to the emergency room as quickly as possible.

A Word from Verywell

If you have allergies to pizza ingredients, you can still have pizza by watching out for your allergens and choosing substitutes. Before biting into a slice, be sure to know what the pizza contains, and talk thoroughly with restaurant staffers about your food allergies before ordering. Once you know it is safe to eat or have found an allergen-free pizza option, you can enjoy one of America’s most popular foods. 

Frequently Asked Questions

  • How long will pizza allergy symptoms last?

    Pizza allergy symptoms can last anywhere from a few hours to days. Sometimes, a second wave of allergy symptoms can occur hours after symptoms of an initial reaction have stopped. This is known as a biphasic reaction.

  • What is the first sign that you’re allergic to pizza?

    The first signs that you’re allergic to pizza can vary. Typically, symptoms such as swelling of the lips or eyelids, skin rashes, or itchy mouth or skin develop within two hours of eating.

  • Will pizza allergens cause itchy skin?

    Pizza allergens such as casein, tomatoes, or yeast may cause itchy skin. However, symptoms other than itchy skin can occur, such as itchy or watery eyes.

9 Sources
Verywell Health 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.
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By Marlo Mittler, MS, RD
Marlo Mittler, MS, RD, is a registered dietitian specializing in pediatric, adolescent, and family nutrition. She is the owner of NutritionByMarlo.