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Food Allergies and Intolerances: Improving Diagnosis and Dietary Management

M3 India Newsdesk Jan 24, 2025

Food allergies and intolerances are both physical reactions to certain foods. This article explains the difference between them, the common types, the causes, symptoms, and the management of food intolerance.


Food allergies and food intolerances

Food allergies are when the immune system reacts to certain foods as if they are harmful. If someone with a food allergy eats the food they are allergic to, their body reacts quickly, causing symptoms ranging from mild, like itching or hives, to severe, like difficulty breathing or anaphylaxis.

On the other hand, food intolerances involve the digestive system rather than the immune system. They happen when the body has trouble digesting certain foods. This can be due to a lack of specific enzymes, like in lactose intolerance, where the body doesn’t have enough lactase to digest lactose.

Food allergies and food intolerances are both physical reactions to certain foods, but they differ in several ways:

  1. Immune system: Food allergies involve the immune system, while food intolerances do not.
  2. Severity: Food allergies can cause severe or life-threatening reactions, while food intolerances are usually less serious.
  3. Symptoms: Food allergies can cause symptoms like hives, vomiting, and breathing problems, while food intolerances can cause nausea, gas, and diarrhoea.
  4. Foods​​​​​​: The most common foods that cause allergic reactions are milk, eggs, fish, shellfish, peanuts, tree nuts, wheat, soybeans, and sesame. Common food intolerances include lactose, casein, and gluten.

Treatment

People with food allergies should avoid the foods that trigger their reactions and carry emergency epinephrine. People with food intolerances can try to avoid or reduce the foods they're intolerant to, but they should not cut them out of their diet without consulting a doctor or dietitian.

Food intolerance symptoms can take several hours to emerge and can persist for several hours or days. The amount of food a person eats determines the severity of their symptoms. Some children outgrow their food allergies as they get older.

Food intolerances affect your digestive system. People who suffer from an intolerance, or sensitivity, can’t break down certain foods. They develop gas, diarrhoea and other problems. An intolerance or food sensitivity is inconvenient but not life-threatening.


What is food intolerance?

When you have a food intolerance, it means your digestive system has a hard time digesting (breaking down) a food. Another word for food intolerance is food sensitivity.

Food intolerance means your gut is sensitive to certain foods and can’t tolerate them. When you eat these foods, you may experience uncomfortable symptoms like gas, diarrhoea and abdominal pain.


What’s the difference between food intolerance and food allergies?

Food intolerance, or food sensitivity, is not the same thing as having a food allergy.

A food intolerance:

  • Affects your digestive system
  • Occurs when your digestive system can’t break down certain foods
  • Causes symptoms like an upset stomach that aren’t life-threatening
  • Brings on symptoms within a few hours after eating as the food makes its way through the digestive tract
  • May not cause symptoms if you eat just a small amount of food

A food allergy:

  1. Affects the immune system.
  2. Occurs when your immune system mistakes a protein or other ingredient in food as a threat. Your immune system releases antibodies (proteins) called immunoglobulin E (IgE) to fight the threat.
  3. Causes an allergic reaction, such as hives and swelling, shortness of breath or wheezing.
  4. Brings on symptoms within minutes of consuming even a small amount of an allergy-inducing food.
  5. May cause a severe, life-threatening reaction called anaphylaxis. Without an epinephrine treatment, this reaction can be fatal.

Common types of food intolerance

Common food sensitivities include:

  1. Lactose: People who are lactose intolerant don’t make enough lactase enzymes to break down lactose, a sugar found in milk and dairy products. This food intolerance is the most common.
  2. Histamine: Histamines are naturally occurring chemicals in foods like cheese, pineapples, bananas, avocados and chocolate. Red wine and some white wines also have histamines. People who are histamine intolerant don’t make enough diamine oxidase enzyme to break down this chemical.
  3. Gluten: Gluten is a protein in wheat, rye and barley. Gluten sensitivity isn’t the same as having celiac disease, a type of autoimmune disease. When you have celiac disease, gluten damages the small intestines. If you have a non-celiac gluten sensitivity, your body has a harder time digesting gluten.

Symptoms and causes

What causes food intolerance?

People with food intolerances often don’t make enough of a particular enzyme that the digestive system needs to break down a certain food or ingredient. Experts aren’t sure why some people develop food intolerances.

Certain gastrointestinal conditions may make you more prone to food sensitivities. These conditions include:

  • Celiac disease
  • Inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis

What are the symptoms of a food intolerance?

Symptoms of a food intolerance include:

  • Abdominal (belly) pain
  • Diarrhoea
  • Gas and bloating
  • Headaches or migraines
  • Heartburn
  • Nausea
  • Upset stomach

Diagnosis and tests

How is a food intolerance diagnosed?

A hydrogen breath test can detect lactose intolerance. During this test, you drink a liquid that has lactose. Then you breathe into a balloon-like container every 30 minutes for a few hours. If you’re lactose intolerant, the undigested lactose will cause high levels of hydrogen in your breath. You may also develop symptoms from drinking the lactose solution.

There isn’t a test for gluten sensitivity or histamine intolerance. An allergy test can detect food allergies but not food intolerance. Your healthcare provider may ask you to keep a food diary to track meals and symptoms.

You may also try an elimination diet to remove certain foods from your diet for two to six weeks. If symptoms go away during this time — and then return when you start eating the food again — you may have a food intolerance.


Management and treatment

You may need to change your diet to limit or eliminate problem foods. Many people with food intolerances find that consuming small amounts of food causes few symptoms if any. When symptoms occur, over-the-counter medicines like antacids or antidiarrheals can help.

People who are lactose intolerant can consume lactose-free milk and dairy products. You can also buy lactase enzymes at drugstores. You can take lactase pills before consuming dairy products or add lactase drops directly to milk to break down the lactose.


Complications of food intolerance

People who are lactose intolerant may not get enough calcium and vitamin D if they completely cut out dairy products. You can take supplements or use over-the-counter lactase enzymes to consume dairy products without getting an upset stomach.

People who cut back on products with gluten may need to eat more fresh vegetables, fruit and gluten-free whole grains to make sure they get enough fibre and other nutrients such as B vitamins in their diets, which are important for health.


Outlook / Prognosis

Food intolerances tend to be lifelong. Most people can manage symptoms if they reduce or cut out foods that cause digestive problems. Food intolerance may be an inconvenience (and the symptoms unpleasant), but it isn’t a life-threatening problem like a food allergy.

A food intolerance can cause stomach upset and other digestive problems after you consume certain foods or drinks. Having a food intolerance isn’t the same as having a food allergy. Food allergies cause an immune system response that can be life-threatening. Most people with food intolerances can have small amounts of those foods without distressing symptoms. A food diary and elimination diet can help determine if you have a food intolerance.

Here are some ways to improve the diagnosis and dietary management of food allergies, intolerances, and sensitivities:

  1. Elimination diet: This is a key part of diagnosing and managing food allergies. It involves removing foods that may be causing an adverse reaction for a period of time, and then reintroducing them to identify which foods are causing symptoms.
  2. Food challenge: This is a procedure that helps confirm or rule out a causal relationship between food and a patient's symptoms.
  3. Allergy-focused history: This includes a patient's family history and a physical examination.
  4. Symptoms: Respiratory, cutaneous, ocular, and cardiovascular symptoms are more suggestive of an allergic process.
  5. IgE-mediated disease: Symptoms involve two or more systems, commonly the skin, gastrointestinal, and respiratory tract.
  6. Non-IgE mediated disease: Symptoms may manifest with only gastrointestinal symptoms.
  7. Hand hygiene: Washing your hands after handling foods that contain common allergens can help prevent cross-contact.

For infants, there are different nutritional management recommendations based on whether they are breastfed or formula-fed:

Breastfed infants: The mother should avoid milk, dairy products, and all cow's milk sources from their diet.

Formula-fed infants: Infants at low risk of anaphylaxis should be given extensively hydrolysed (eHF) infant formula. Infants at high risk of anaphylaxis should be given an amino acid-based formula.

Elimination diets constitute a reliable alternative to food sensitivity testing for identifying nonallergic food intolerances at a low cost. Although elimination diets are available, they require more effort and commitment on the part of clients, so dietitians must use their judgment in identifying the best candidates for this approach.


Elimination phase

Depending on the practitioner, the protocols used when implementing an elimination diet can vary slightly, but generally, they include an elimination and reintroduction phase. During the elimination phase, which should last between four and eight weeks depending on the severity of the client’s symptoms, all potentially problematic foods must be avoided and replaced with safer alternatives.


Reintroduction phase

Once the elimination phase has resulted in significant health improvements, RDs can assist clients throughout the reintroduction phase, during which eliminated foods are systematically reintroduced into the diet one at a time and every few days to assess tolerance. Any foods that trigger previous symptoms should be considered problematic and avoided. Foods that don’t appear to cause any reaction are deemed safe to reintroduce and can become part of the client’s regular diet if desired.

“Although there are trigger foods or chemicals that are considered more common allergens and others that are more heavily associated with certain diseases, our immune systems still have the final say as to what our inflammatory triggers are,” Linke says. “There are no universal anti-inflammatory foods.”

 

Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Pallavi Dubey has done a Master's in Clinical Nutrition & Dietetics, currently working as a Senior Clinical Nutritionist at Recoup Health, Bangalore.

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