What is Food Allergies?
A food allergy is when your immune system reacts to certain proteins in food. This reaction can be triggered by something called immunoglobulin (Ig)E or may not involve IgE at all. For clarity, IgE is a type of substance in your body that can cause an allergic reaction. This type of food allergy is a global health issue that impacts millions of people and can affect many parts of their lives. Eating food that you’re allergic to can cause a wide range of symptoms, affecting your skin, digestive system, and breathing.
The exact number of people with a food allergy is not known, but it seems like these kinds of allergies have become more common over the past 30 years. This increase is mostly happening in countries that typically have a Western lifestyle.
While any food could lead to an allergic reaction, most food allergies are caused by a small number of foods. This includes milk, eggs, peanuts, shellfish, wheat, and nuts. Several severe reactions to food, some nearly fatal, have been reported in recent years. However, it’s important to note that if your body’s immune system isn’t involved in the reaction, it’s not a food allergy. For example, if you have trouble digesting milk, that doesn’t mean you’re allergic to it—it just means you’re intolerant to milk.
What Causes Food Allergies?
Food allergies can develop in two ways, depending on what triggers the body’s reaction. One way is through what’s termed IgE-mediated or type I hypersensitivity. The second way is through reactions that don’t involve IgE. IgE is a type of molecule that your immune system produces when it overreacts to a substance, like certain foods.
The substances in food that cause allergies are generally water-soluble glycoproteins. These are a type of protein that is hard to break down and can easily move across the lining of the intestine.
Certain factors can increase your risk for severe food allergies, or anaphylaxis, which is a severe, potentially life-threatening allergic reaction. These include having asthma, having experienced anaphylaxis before, or a delay in the use of epinephrine – a medication used to treat severe allergic reactions.
Risk Factors and Frequency for Food Allergies
About 6% of kids have allergic reactions to some foods during their first three years of life. This includes around 2.5% with an allergy to cow’s milk, 1.5% that are allergic to eggs, and 1% that have a peanut allergy. Research has found that peanut allergies have become more common over the last ten years. However, most kids stop being allergic to milk and eggs by the time they reach school age. On the other hand, allergies to peanuts, nuts, and seafood usually stay with a person for their whole life.
- Approximately 6% of children have food allergies in their first three years.
- Of these, 2.5% are allergic to cow’s milk, 1.5% have an egg allergy, and 1% have a peanut allergy.
- There has been an increase in the prevalence of peanut allergies over the past decade.
- Most children outgrow their milk and egg allergies by the time they start school.
- Allergies to peanuts, nuts, and seafood usually persist throughout a person’s life.
Signs and Symptoms of Food Allergies
Food hypersensitivity disorders, also known as food allergies, can affect different parts of the body. They can cause a variety of signs and symptoms depending on the organ they predominantly target and the immune system’s response.
A food allergy can affect the digestive system, especially in infants and young children. They may become irritable, vomit, have diarrhea, and fail to gain weight properly. There are three main forms of food allergies that lead to digestive symptoms:
- Food Protein-Induced Enterocolitis Syndrome (FPIES): This can cause vomiting one to three hours after eating. Constant exposure can lead to a swollen belly, bloody diarrhea, anemia, and issues with weight gain. This is typically caused by cow’s milk or soy-based formula.
- Food Protein-Induced Proctocolitis: This usually leads to streaks of blood in a healthy infant’s stool within the first few months of life, particularly among breastfed infants.
- Food Protein-Induced Enteropathy: This can cause steatorrhea (excessive fat in stools) and poor weight gain in the early months of life.
Food allergies can also affect the skin, as seen in cases of:
- Atopic dermatitis, or eczema: Around 30% of children with moderate to severe eczema have food allergies.
- Acute urticaria and angioedema: These are common symptoms of food allergies that can begin quickly after ingesting the allergen. Foods such as eggs, milk, peanuts, nuts, sesame and poppy seeds, and fruits like kiwi are common triggers.
- Perioral dermatitis: This is a harmless condition often caused by substances in toothpaste, gum, lipstick, or medication, and it tends to go away on its own.
Food allergies can also potentially affect the respiratory system:
- Respiratory food allergies are rare as standalone symptoms. Wheezing happens in about 25% of food allergies driven by a specific type of immune response (IgE-mediated). However, only around 10% of asthma patients experience food-induced respiratory symptoms.
Testing for Food Allergies
If you or your doctor think you might have a food allergy, the first steps to diagnose it include a detailed analysis of your medical history and a thorough physical examination. The medical history helps in understanding a severe allergic reaction you might have experienced, identifying the possibly offending food, and figuring out the type of allergy. To offer more detailed information about what you eat on a daily basis, it could be beneficial to keep a food diary. This could be especially helpful in the case of chronic allergies where symptoms aren’t as immediately apparent as in acute allergies.
The physical examination often provides indications of whether you might be dealing with an allergic reaction or any allergy-related condition associated with certain foods.
If these steps are inconclusive in identifying the specific food allergen causing your reactions, allergy testing can be carried out. Skin prick tests (SPTs) are a quick method often used for identifying sensitivity to a specific food. However, they aren’t foolproof as even if the result is positive, actual symptomatic food allergies only happen in about 40% of the cases. A negative test, on the other hand, generally suggests the absence of a specific food allergy.
Due to such uncertainties with SPTs, more specific tests like measuring the level of food-specific IgE antibodies in your blood or testing your body’s response to temporary food elimination might be required. Higher levels of these antibodies often mean an increased chance of an allergic reaction. If your levels are over a certain limit, it is very likely (>95%) you’ll show allergic reactions to related foods.
In some cases, a more rigorous food challenge test might be needed. This involves temporarily avoiding potential allergy-causing foods for a period of 7 to 14 days before reintroducing them to see if symptoms reappear. This is considered the most reliable test for a food allergy. During this test, some typical allergy symptom-relief medications might need to be stopped. If even after avoiding potentially allergy-caicusing foods, your symptoms do not improve, food allergies may not be the root cause of your issues. In the few instances where food challenge tests give a false-negative result, another open and supervised food challenge may be carried out to confirm the result.
Treatment Options for Food Allergies
If you’ve been diagnosed with food hypersensitivity or a food allergy, the main form of treatment is to steer clear of any foods that trigger your allergies. There isn’t a cure for food allergies, so learning how to manage them is crucial.
For both children with food allergies and their parents, it’s important to understand how to read food labels to know what’s in the foods you’re eating. You’ll also need to be aware of potential hidden allergens in restaurant meals, and avoid behaviors that could lead to unintentional exposure to allergy-inducing foods. If there’s a risk that you might have a severe allergic reaction called anaphylaxis, you should be trained to recognize the early signs of this condition. You also need to know how to use an auto-injectable device that delivers a dose of a medication called epinephrine, and always have both this device and antihistamine medications on hand.
If you have a food allergy and also have asthma, or if you’ve previously had a severe allergic reaction, or are allergic to peanuts, nuts, seeds, or seafood, you should have easy access to self-injectable epinephrine and have a written plan in case you accidentally eat something you’re allergic to. It’s worth noting that while some food allergies can decrease or disappear over time, allergies to peanuts, nuts, and seafood usually don’t. Children who are allergic to peanuts, but who have low levels of a certain type of immune cells called peanut-specific IgE, should be checked periodically to see if their allergy is still as strong.
When it comes to preventing food allergies, the current advice is to start giving infants a variety of solid foods, such as egg, peanut products, fish, wheat, and other potentially allergy-inducing foods, one at a time, from four to six months of age. If the infant is breastfeeding, there’s no need to hold off on introducing these foods.
What else can Food Allergies be?
The following are some medical conditions that could be considered when making a diagnosis:
- Factitious disorder
- Esophagitis and esophageal motility disorders
- Giardiasis
- Gastroesophageal Reflux Disease (GERD)
- Irritable Bowel Syndrome (IBS)
- Bacterial or viral gastroenteritis (stomach flu)
- Lactose intolerance
- Whipple disease
What to expect with Food Allergies
As children grow, many of them become tolerant or outgrow their food allergies, especially to common allergens like eggs, milk, wheat, and soy. However, allergies to nuts and shellfish usually persist longer. Around 20% of children no longer have their food allergy by the time they start school. The food allergies that resolve in the first year of life are those not triggered by IgE, a type of protein that plays a key role in allergic reactions. Regrettably, serious allergic reactions leading to fatal anaphylaxis, a severe, potentially life-threatening allergic reaction, still occasionally occur.
Possible Complications When Diagnosed with Food Allergies
Possible Severe Reactions:
- An allergic reaction that is severe and possibly life-threatening (anaphylaxis)
- Breathing difficulties (respiratory distress)
- A sudden stop in heart function (cardiac arrest)
