4 Reasons Tomatoes Can Upset Your Stomach
Tomatoes are a popular and versatile fruit (yes, fruit!) packed with nutrients like vitamin C and antioxidants. However, for some people, tomatoes and tomato-related products like tomato soup and tomato sauce can cause an upset stomach and other symptoms, including diarrhea.
Here are four common reasons that tomatoes can upset your stomach and what you can do about each one.
1. You Have a Food Intolerance
- Cramping and gas pains
- Diarrhea
- Constipation
Poor absorption of fructose is thought to be one of the dietary triggers for irritable bowel syndrome and could be the reason why tomatoes give you diarrhea.
But keep in mind that a little tomato here and there may be fine. "Small amounts of tomatoes may not cause a problem, but where some people get tripped up is with canned tomatoes or tomato-based products like ketchup and pasta sauce," says Kristin West, RD. "These other products tend to have additives like high-fructose corn syrup or garlic, and that can take you into the high-FODMAP zone."
So if you were wondering why tomato sauce gives you diarrhea or hurts your stomach, these ingredients could be to blame. Tomato soups and juices can also contain additives that may not agree with your stomach, so be sure to read the labels.
Fix it: If symptoms become problematic, it's best to have your doctor or a dietitian help you plan a diet around your restrictions so you can avoid an upset stomach and diarrhea after eating tomatoes.
2. You Have a Food Allergy
In response to an allergen, antibodies, histamines, and other chemicals are released into the bloodstream, which cause symptoms. According to Ashley Kravitz, RD, owner of Nutrition Specialists of New Jersey, these symptoms might include the following on the skin or mouth:
- Tingling
- Itching
- Numbness
- Redness
It's also possible that an allergy to tomatoes could cause diarrhea and symptoms similar to those of fructose intolerance, she says:
- Abdominal cramps
- Nausea
- Vomiting
- Diarrhea
Fix it: It can be easy to confuse a food allergy with a food intolerance. If you have any of the above symptoms after eating tomatoes, see your doctor or an allergist, who can help you figure out the root cause.
3. It's Actually Heartburn
"Many people experience heartburn after consuming tomatoes because of their strong acidity. The human gastrointestinal tract produces gastric acid to break down foods that are sitting in your stomach, and when you consume acidic foods such as tomatoes, it can cause heartburn to act up," Kravitz says.
The discomfort may feel like an upset stomach, but the pain could actually be coming from an irritated throat. Other symptoms of acid reflux can include the following:
- Coughing
- Problems swallowing
- The feeling of food caught in your throat
- Sore throat
- Hoarse voice
- Vomiting
Fix it: Heartburn can usually be managed with over-the-counter meds and other acid reflux remedies like eating smaller portions and remaining upright for a couple of hours after eating. If you frequently experience heartburn, consult a doctor who can help identify the cause and develop a personalized treatment plan.
4. You've Got Food Poisoning
Food poisoning from tomatoes can cause diarrhea, along with an upset stomach and the following other symptoms:
- Fever
- Vomiting
- Stomach cramps
- Dehydration
The Takeaway
- Tomatoes are an excellent source of vitamin C and antioxidants.
- For some people, eating tomatoes can cause stomach upset or other digestive issues due to tomato-related food intolerance, allergies, food poisoning, or acid reflux.
- If you experience discomfort from eating tomatoes, speak to your doctor about prevention or a treatment plan.
- Food allergy vs. food intolerance: What's the difference? Mayo Clinic. February 28, 2024.
- Try a FODMAPs diet to manage irritable bowel syndrome. Harvard Health Publishing.
- Sia T et al. Fructose malabsorption and fructan malabsorption are associated in patients with irritable bowel syndrome. BMC Gastroenterology. April 24, 2024.
- Food Allergy. Mayo Clinic. August 30, 2024.
- Facts and Statistics. Food Allergy Research & Education.
- Włodarczyk K et al. Tomato Allergy: The Characterization of the Selected Allergens and Antioxidants of Tomato (Solanum lycopersicum)—A Review. Antioxidants. March 28, 2022.
- Oral Allergy Syndrome (OAS). American Academy of Allergy, Asthma & Immunology. January 10, 2024.
- Acid Reflux & GERD. Cleveland Clinic. September 28, 2023.
- Food poisoning (foodborne illness). Mayo Clinic. August 16, 2025.
- About Botulism. Centers for Disease Control and Prevention. April 18, 2024.
- Kendall P et al. Canning Vegetables. Colorado State University. September 2025.
- Foodborne Illness. Mayo Clinic. August 6, 2024.
Ira Daniel Breite, MD
Medical Reviewer
Ira Daniel Breite, MD, is a board-certified internist and gastroenterologist. He is an associate professor at the Icahn School of Medicine at Mount Sinai, where he also sees patients and helps run an ambulatory surgery center.
Dr. Breite divides his time between technical procedures, reading about new topics, and helping patients with some of their most intimate problems. He finds the deepest fulfillment in the long-term relationships he develops and is thrilled when a patient with irritable bowel syndrome or inflammatory bowel disease improves on the regimen he worked with them to create.
Breite went to Albert Einstein College of Medicine for medical school, followed by a residency at NYU and Bellevue Hospital and a gastroenterology fellowship at Memorial Sloan Kettering Cancer Center. Working in city hospitals helped him become resourceful and taught him how to interact with people from different backgrounds.
