3 Reasons Tomatoes Might Cause Diarrhea or Other Digestive Symptoms

Although tomatoes and tomato products like spaghetti sauce are popular in the Western diet, some people have a hard time digesting them, which can lead to diarrhea and other digestive issues.

If tomatoes upset your stomach, you may have a tomato intolerance or sensitivity, tomato allergy or food poisoning. Here's a look at the possible culprits.

It's possible to have an intolerance to tomatoes, which would make tomatoes hard for your body to digest, according to the Cleveland Clinic.

Common signs of a food intolerance or sensitivity include:

• Diarrhea
• Bloating and gas
• Nausea
• Stomach upset
• Heartburn
• Headaches

Some people may experience these symptoms after eating a small amount of tomato, while others might be fine with smaller servings but have a reaction to larger quantities of tomatoes.

A food intolerance is not the same as a food allergy (more on that below), per the Mayo Clinic. While an intolerance often leads to digestive issues, a true food allergy more often causes respiratory or skin-related issues (think: hives, trouble breathing).

​Fix it:​ If you think you might have a tomato intolerance, keep track of your symptoms and when they appear. Depending on how sensitive you are, you might want to cut back on how many tomatoes you're eating or cut them out of your diet altogether to avoid symptoms.

It's also a good idea to tell your doctor about your symptoms. They can help you determine if an intolerance is the true culprit and suggest any further testing or treatments.

A food allergy is an abnormal immune response to a protein in a food. Tomato allergies are rare, but as with any allergic reaction, they can sometimes be life-threatening.

Symptoms of a food allergy include the following, according to the American Academy of Family Physicians (AAFP)

• Hives
• Swelling
• Itchy skin
• Itching or tingling in the mouth
• Metallic taste in the mouth
• Respiratory symptoms: coughing, wheezing or trouble breathing
• Tightness in the throat
• Diarrhea
• Abdominal cramps
• Vomiting

The AAFP says allergic reactions are often caused by raw foods only; cooking may distort the protein allergens so the immune system does not recognize them as a foreign substance. Some people find they can tolerate ketchup, spaghetti sauce and pizza but not raw tomatoes, for example.

​Fix it:​ If you think you have a tomato allergy, it's important to see an allergist. They may give you a scratch test or blood test that can identify the cause of your reaction to eating tomatoes. If you're allergic, you'll want to stop eating tomatoes to avoid any potentially dangerous symptoms.

It may not be the tomatoes themselves causing your symptoms, but rather a contaminant. Sometimes unwashed produce can contain disease-causing bacteria like ​Salmonella​, ​E. coli​ or ​Listeria​, according to the Centers for Disease Control and Prevention (CDC).

Symptoms of food poisoning include the following, per the CDC:

• Stomach upset or cramps
• Nausea
• Vomiting
• Diarrhea
• Fever

​Fix it:​ There's no cure for food poisoning, but symptoms are usually temporary and best managed by resting and staying hydrated. To avoid food poisoning from tomatoes, make sure to wash them thoroughly before eating and use clean surfaces and utensils when preparing them, per the CDC.