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Food allergies vs. intolerances: How to identify and manage them

Food allergies vs. intolerances: How to identify and manage them The difference between food allergies and food intolerance (photo:

People often have unpleasant reactions to various foods, and the first thought is usually about food allergies. However, there is another reaction—intolerance to certain foods. According to doctors, these are completely different reactions of the body. WebMD explains the difference between food allergies and intolerances.

What is the difference?

Food allergies are caused by your immune system reacting to food when it doesn't need to. On the other hand, your immune system is not responsible for food intolerance. It is usually associated with problems digesting food.

For example, a milk allergy is different from the inability to digest it due to lactose intolerance properly.

Some people come from families where allergies are common—not necessarily food allergies, such as hay fever, asthma, or hives. If both parents suffer from allergies, the child is more likely to get a food allergy.

If you suspect a food allergy, you should see a doctor to find out what is causing it and get the necessary consultation and treatment. Sometimes, allergic reactions to food can be severe and even life-threatening.

How food allergies manifest

IgE or non-IgE proteins cause food allergies, and how they affect cells found in all tissues of the body, especially in places like the nose, throat, lungs, skin, and digestive tract. IgE stands for immunoglobulin E, a type of protein called an antibody that travels through the blood.

When you first eat a food you are allergic to, certain cells produce a lot of IgE to the part of the food that causes the allergy, called the allergen. IgE is released and attaches to the surface of mast cells. You won't react yet, but now you are ready for it.

The next time you eat this food, the allergen interacts with this IgE and causes mast cells to release chemicals such as histamine.

These chemicals cause different symptoms depending on the tissue where they are located. Since some food allergens are not broken down by heat during cooking, stomach acids, or digestive enzymes, they can enter the bloodstream. From there, they can travel and cause allergic reactions throughout the body.

The digestion process affects the time and place. You may feel itching in your mouth. Then, you may have symptoms such as vomiting, diarrhea, or stomach pain.

Food allergens in the blood can cause a drop in blood pressure. When they reach the skin, they can cause hives or eczema. In the lungs, they can cause wheezing. All this happens within a few minutes to an hour.

Non-IgE-mediated food allergy is characterized by delayed onset of signs and symptoms, which can appear within a few hours or even days after eating.

Common food allergens

  • Peanuts
  • Tree nuts, walnuts
  • Shellfish, including shrimp, crawfish, lobsters, and crabs

Children often have allergies to:

  • Eggs
  • Milk
  • Peanuts

Adults usually do not outgrow allergies, but children may outgrow some allergies with age. They are more likely to outgrow allergies to milk, eggs, and soy than to peanuts, fish, and shrimp.

Additionally, there are foods you may react to that you eat regularly. In Japan, rice allergies are common, while in Scandinavia, cod allergies are common.

Dangerous allergic reaction

If you have a life-threatening allergic reaction to certain foods, your doctor will likely advise you to avoid such products.

For example, if you are allergic to shrimp, you are likely allergic to other shellfish, such as crab, lobster, and crawfish. This is called cross-reactivity.

Another example of cross-reactivity is oral allergy syndrome. This happens to people who are highly sensitive to ragweed. During ragweed season, when they try to eat melons, especially cantaloupe, they may experience itching in their mouth. Similarly, people with severe birch pollen allergies may also react to apple skins.

Allergies, but not to foods. Onee type of food allergy requires more than just consuming the allergen to trigger a reaction. If you havean exercise-induced food allergy, you will not have a reaction unless you engage in some physical activity.

When your body temperature rises, you may start itching, feel dizzy, get hives, or even experience anaphylaxis.

Fortunately, the remedy is simple: avoid eating allergens a couple of hours before exercising.

Is it really a food allergy?

Differential diagnosis is distinguishing between food allergy, food intolerance, and other conditions. When you visit a doctor, they need to consider other things that might cause similar symptoms. These include:

  • Food poisoning
  • Histamine toxicity
  • Food additives, including sulfites, monosodium glutamate, and dyes
  • Lactose intolerance
  • Gluten intolerance
  • Other diseases
  • Psychological triggers

Food can be contaminated with bacteria and toxins. Spoiled meat sometimes mimics a food allergy, although it is a type of food poisoning.

Histamine can reach high levels in cheese, some wines, and certain types of fish, especially tuna and mackerel, if not properly refrigerated. When you eat foods with a high amount of histamine, you can experience a reaction similar to an allergic reaction. This is called histamine toxicity.

Sulfites are naturally formed during wine fermentation and are added to other foods to enhance crispness or prevent mold growth. However, high concentrations of sulfites can create problems for people with severe asthma.

They release a gas called sulfur dioxide, which is inhaled while eating. This irritates their lungs and can trigger an asthma attack. The FDA has banned sulfites as preservatives for fresh fruits and vegetables. However, sulfites are still used in some foods.

Monosodium glutamate (MSG) naturally occurs in tomatoes, cheese, and mushrooms. It is added to other foods to enhance flavor. When consumed in large quantities, MSG can cause flushing, warmth, headache, facial pressure, chest pain, or a sense of detachment.

Yellow dye No. 5 can cause hives, though this is rare.

Lactose intolerance

Lactose intolerance, the most common food intolerance, affects at least 1 in 10 people. Lactase is an enzyme in the lining of the intestine. It breaks down lactose, a sugar in milk and other dairy products. If you don't have enough lactase, you won't be able to digest lactose. Instead, bacteria eat the lactose, which produces gases, and you may experience bloating stomach pain, and diarrhea. Your doctor can measure your body's reaction to lactose by examining blood samples.

Gluten intolerance

Gluten intolerance is not the same as celiac disease. Celiac disease is caused by an abnormal immune response to gluten, a protein in wheat and other grains. Gluten intolerance, on the other hand, is related to how the digestive system processes gluten. Both of these conditions are different from food allergies.

Symptoms of other conditions

Symptoms of some other diseases can mimic food allergies, including ulcers and cancers of the digestive system. These can cause vomiting, diarrhea, or pain that worsens when eating.

Psychological triggers

Some people may have food intolerance with a psychological trigger. An unpleasant event often occurring in childhood related to consuming a particular food can trigger discomfort when you eat that food later, even in adulthood.

Diagnosing food allergies

If your doctor suspects a specific food allergy, you may undergo tests to measure your allergic reaction.

One of these is a skin prick test. The doctor drops a solution made from the food on your forearm or back. They then prick the skin with a needle through the drop and watch for swelling or redness.

Skin tests are quick, easy, and relatively safe. However, experts do not recommend diagnosing solely based on a skin test. Your skin test might show an allergy to a food, but you might not experience allergic reactions when you eat that food. Thus, your doctor will diagnose a food allergy only if you have a positive skin test and a history of responses to the same food.

Skin tests can be dangerous if you have severe allergies and serious reactions. They also can't be done if you have severe eczema. Instead, your doctor may use blood tests that measure the amount of food-specific IgE. Again, a positive result does not necessarily mean you have a food allergy.

A food challenge or feeding test is another way to confirm or rule out an allergy. You eat small portions of food every 15-30 minutes, containing increasing amounts of the suspected allergen until you have a reaction or eat a meal-sized portion.

Unproven methods of diagnosing food allergies

Some methods cannot effectively detect food allergies. These include:

Cytotoxicity testing: A food allergen is added to a blood sample. A technician then examines the sample under a microscope to see if white blood cells die.

Sublingual or subcutaneous provocation challenge: This is similar to a skin test, but a sample of the food allergen is placed under the tongue or injected under the skin.

Immune complex assay: This blood test looks for clusters of specific antibodies related to the food allergen. These clusters usually form during food digestion, and with sufficiently sensitive measurements, they are present in everyone.

IgG subclass analysis: This blood test looks explicitly for certain types of IgG antibodies, but they are part of the normal immune response.

Treatment of food allergies

The primary way to manage a food allergy is to avoid the allergen. Even a tiny amount of the allergen (just 1/44,000th of a peanut kernel) can trigger a reaction in people with severe allergies. Less sensitive individuals may be able to consume small amounts of the allergenic food.

Once you identify the offending food, you need to stop eating it. This may mean reading long and detailed ingredient lists because many allergenic foods are found in products where you wouldn't expect them.

For example, peanuts might be included as a protein source, and eggs can be found in some salad dressings. You may need to ask about the ingredients in specific dishes or cuisines in restaurants.

If you have had anaphylactic reactions to food, you should wear a medical alert bracelet. You should also carry two epinephrine auto-injectors and be prepared to use them if you think a reaction is starting.

Mild symptoms, such as tingling in the mouth and throat or an upset stomach, may not be an allergic reaction, but you should still inject yourself. It won't hurt and might save your life. Then call emergency services.

Medications to help alleviate food allergy symptoms

Medications can help alleviate food allergy symptoms that are not part of an anaphylactic reaction:

  • Antihistamines for digestive issues, hives, sneezing, and runny nose.

  • Bronchodilators for airway constriction or asthma-like symptoms.

However, they do not prevent an allergic reaction if taken before eating. No medications can. Placing a diluted solution of the food under the tongue about half an hour before eating as a way to "neutralize" the effect also does not work.

Allergy pills and shots

Allergy pills and shots are being studied as a way to reduce people's sensitivity to food allergens. You regularly receive small amounts of food extracts over a long period to help your body develop a sort of tolerance. But researchers have not yet proven that allergy shots are effective for food allergies.

Food allergies in infants and children

Milk and soy allergies are particularly common in infants and young children, likely because their immune and digestive systems are still developing.

These allergies can arise within a few days or months after birth. They may not manifest as hives and asthma but rather lead to colic and possibly blood in the stool or poor growth.

Typically, a doctor sees a very unhappy baby suffering from colic, who may not sleep well at night, and diagnoses a food allergy, partly by changing their diet, such as switching from cow's milk to soy formula. This type of allergy tends to disappear within a few years.

Doctors recommend breastfeeding infants exclusively for the first 4-6 months, if possible, for many reasons, but there is no evidence that this prevents food allergies later in life.

Although some pregnant women may hope that restricting their diet during pregnancy or breastfeeding will help their children avoid allergies, experts disagree and do not recommend this. Soy formulas are also not a good way to prevent allergies.

Problems mistakenly associated with food allergies

While some people speculate that certain conditions may be caused by food allergies, the facts do not support such claims. For example, histamine in cheese or red wine can trigger migraines, but we cannot say that food allergies truly cause migraines.

Rheumatoid arthritis and osteoarthritis are not worsened by food. Food allergies do not cause "allergic tension-fatigue syndrome," where people feel tired and nervous, have trouble concentrating, or experience headaches.

Even if the environment is very clean, some people experience a range of general complaints, such as concentration problems, fatigue, or depression. Environmental illnesses may result from a small number of allergens or toxins, but not food allergies.

Researchers have found that hyperactivity in children can be related to food additives, but only rarely and only when the child has consumed a lot of them.

Food allergies do not directly impact a child's behavior, although their symptoms can make them irritable and difficult, and allergy medications can make them drowsy.

This material is for informational purposes only and should not be used for medical diagnosis or self-treatment. Our goal is to provide readers with accurate information about symptoms, causes, and methods of detecting diseases. RBС-Ukraine is not responsible for any diagnoses that readers may make based on materials from the resource. We do not recommend self-treatment and advise consulting a doctor in case of any health concerns.