The Dangers of Self-Diagnosed Food Allergies

Just because you experience nausea, bloating, headaches, or other symptoms after eating a particular food, this doesn't necessarily mean you are allergic to it. Self-diagnosing food allergies presents certain dangers. Malabsorption syndrome, food intolerance, functional abnormalities, even cancer can all share signs of a food allergy. If you truly believe you are allergic to certain foods, it's best to seek the advice of your healthcare provider.


Do You Have a Food Allergy?

What if you eat a food and it causes stomach problems? Could you have a food allergy? Common symptoms of food allergies include:
  • Vomiting
  • Nausea
  • Diarrhea
  • Abdominal (stomach) pain
  • Gas
  • Bloating.
These symptoms can occur several hours after a meal. If you experience any of them, should you assume you are allergic and eliminate the food from your diet? It turns out that a food allergy is only one of many conditions that can cause digestive issues. Seeking the advice of a qualified healthcare professional is the safest way to discover the source of the problem.

Diagnostic Tests

A true food allergy is caused by an immune response against substances found in food. People with food allergies often have antibodies that react with one or more plant- or animal-derived proteins. The body treats the proteins, or allergens, as a threat, even though they are harmless. Because of the irritating effect of the immune response, symptoms appear every time the food is eaten.
Food allergies are diagnosed based on a person's medical history, skin and blood tests, and, occasionally, biopsies of the digestive tract. The "gold standard" of food allergy testing is the double-blind food challenge, where a person eats capsules containing various foods. The capsules are opaque, and neither the doctor nor the person knows what is in each one, allowing an unbiased test. Digestive problems occur after the person swallows a capsule containing the food allergen.
About 1 percent of adults have celiac disease, an immune response against gluten proteins in wheat, rye, and barley that can damage the small intestine. Allergies to peanuts, tree nuts, fish, and shellfish are more common. Approximately 20 percent to 30 percent of adults believe they have a food allergy, but only 3 percent to 4 percent can identify a food allergen using the challenge test. Some conditions that mimic food allergies are:
As you can see, getting a proper diagnosis is important because some of these conditions may be life threatening.
Food Intolerance
This category includes a number of nonallergic food hypersensitivities. Although the foods cause digestive upset in different ways, what they have in common is that the immune system is not involved. 
Malabsorption Syndromes
Individuals with lactose intolerance cannot digest lactose, a sugar in milk, and people with fructose malabsorption cannot absorb much fructose, or fruit sugar, in the small intestine. Bacteria in the colon metabolize the excess sugar, producing gas that leads to bloating, abdominal pain, and diarrhea.
People with European ancestry are less prone to lactose intolerance, but about 40 percent have fructose malabsorption. Both conditions can be diagnosed with a hydrogen breath test or other types of medical tests and treated with simple dietary modifications.
Functional Abnormalities
About 10 percent to 20 percent of adults in the United States suffer from gastroesophageal reflux (GERD), where the stomach contents flow back into the esophagus and cause irritation. With this condition, eating certain foods can lead to heartburn and gas. Common foods include:
  • Peppermint
  • Onions
  • Chili peppers
  • Fatty foods.
People who suspect they have GERD should be diagnosed and treated by a doctor, since damage to the esophagus over time from the acidic stomach contents can cause strictures and cancer.
Irritable bowel syndrome (IBS) with diarrhea can also be mistaken for a food allergy. IBS is one of the most common digestive disorders, occurring in 5 percent to 15 percent of women. Foods that may trigger abdominal pain, bloating, and diarrhea include:
  • Dairy products
  • Broccoli
  • Gluten
  • Chocolate.
Since there are no specific tests for IBS, diagnosis depends on symptoms and physical examination. Treatment is highly individualized, often involving lifestyle changes and medication.
Pharmacological Reactions
In sensitive individuals, chemicals found in food can act like drugs that have negative side effects. Some examples are histamine and monosodium glutamate (MSG). Scombroid poisoning results from eating fish that has been improperly refrigerated. Bacterial growth on the fish generates large amounts of histamine, which is resistant to cooking. Fish associated with scombroid poisoning include tuna, mackerel, mahi mahi, and sardines. Antihistamines usually relieve the symptoms of flushing, headache, abdominal cramps, and diarrhea.
MSG is an amino acid used as a flavor enhancer in Asian food. "Chinese restaurant syndrome" involves nausea, muscle pain, sweating, and headaches that occur after eating food that contains MSG. Despite its reputation, clinical trials have failed to show a clear relationship between eating MSG and the symptoms described here. Although some people may be truly sensitive to MSG, studies suggest that other substances, such as a combination of high fat and sodium, trigger the symptoms.
Various types of infections in the digestive tract can duplicate the symptoms of food allergies. Peptic ulcers, often caused by H. pylori bacteria, can lead to heartburn, gas, and abdominal pain several hours after meals. H. pylori is detected by the urea breath test, antibody tests, and endoscopy. It can be eliminated by a combination of drugs that are usually given for 10 to 14 days.
Adults who ingest contaminated water can become chronically infected with a parasite called Giardia lamblia. Diarrhea, abdominal cramps, gas, and nausea are common symptoms. Giardia infection, or giardiasis, is diagnosed by testing stool samples and can be treated with antibiotics.
Pain that occurs with a fever, nausea and vomiting, or loss of appetite may be a sign of inflammation or infection of the gallbladder. People often experience symptoms within 90 minutes of eating a meal, particularly one containing fatty foods. Suspected gallbladder problems can usually be confirmed or ruled out by diagnostic imaging.
Any change in bowel habits, such as persistent diarrhea or rectal bleeding, could be signs of cancer. Nausea, vomiting, and abdominal discomfort are sometimes symptoms of colorectal cancer, along with weakness or fatigue. People with these types of symptoms should see a healthcare provider as soon as possible.
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