June 8, 2023
Article Disease

What are Allergies?

An allergy arises when your body’s natural defences overreact to a material, seeing it as an enemy and releasing chemicals to protect against it.


Over 50 million Americans have an allergy. You’ve undoubtedly met or are one of these people. 4–6% of children and 4% of adults have food allergies, according to the CDC.

Food allergy symptoms are most frequent in babies and toddlers but can strike anyone. You can be allergic to foods you’ve consumed for years.

Signs of allergies

The immune system fights infections and other threats to health. When your immune system overreacts to a meal or food ingredient, it triggers a defensive response.

Food allergies tend to run in families, but it’s impossible to tell if a child will inherit a parent’s or a sibling’s. Some study suggests a peanut-allergic child’s younger siblings will be allergic, too.

An allergy’s symptoms can be moderate or severe. Just because an initial reaction is moderate doesn’t guarantee all reactions will be the same; a food that caused mild symptoms one time may induce more severe symptoms another time.

The most severe allergic reaction is anaphylaxis, a whole-body reaction that can limit breathing, lower blood pressure, and disrupt heart rate. Anaphylaxis can occur minutes after eating the trigger food. It can be fatal and must be treated with epinephrine (adrenaline).

While any food can produce a reaction, eight categories account for 90% of all reactions. Sesame is the 9th most common food allergy and appears in hummus under the name “tahini.” According to the FDA, sesame will be the 9th major food allergy starting in 2023. Until then, manufacturers don’t have to identify it as an allergen, but it must be in the ingredient statement. When sesame is a natural flavouring or spice, it’s okay.

An allergic reaction can affect the skin, gut, heart, and lungs. In one or more of the following ways:

Most food-related symptoms appear within two hours; sometimes minutes. In rare circumstances, the effect may be delayed by 4 to 6 hours. Delayed reactions are particularly common in children with food-induced eczema and adults with a rare red meat allergy caused by a lone star tick bite.

Another type of delayed food allergy reaction is food protein-induced enterocolitis syndrome (FPIES), a severe gastrointestinal reaction that occurs two to six hours after eating milk, soy, cereals, and other solid foods. It mostly affects newborns who are initially exposed to certain meals or being weaned. FPIES can cause dehydration through vomiting. Some babies get bloody diarrhoea. Because symptoms mirror a viral or bacterial infection, FPIES may be misdiagnosed. IV rehydration is needed to treat FPIES.

Not everyone who suffers symptoms after eating specific foods has a food allergy or needs to avoid that meal. For example, some people have an itchy mouth and throat after eating raw or uncooked fruits or vegetables. This may be oral allergy syndrome, a reaction to pollen, not food. Pollen and related proteins in food trigger an allergic reaction in the immune system. The allergen is destroyed by heating the meal, making it safe to eat.

Taking care of [Giselle’s] necessities has allowed her to fly.


Avoiding food is the best treatment for a food allergy. The most common food allergies in kids are:

Milk and egg allergies can be outgrown. Peanut and tree nut sensitivities persist.

Common allergies in adults are:

People allergic to one food may respond to related ones. A tree nut allergy might cross-react with others. Shrimp allergies can affect crab and lobster. Someone allergic to peanuts, which are legumes (beans), not nuts, may be allergic to tree nuts including pecans, walnuts, almonds, and cashews. In rare cases, they may be allergic to other legumes (excluding soy).

Food allergy patients should see a board-certified allergist to learn about cross-reactivity and what to avoid. Determining cross-reactivity is tricky. Given how similar two food items in a “family” may look to the test, allergy testing for numerous in the same “family” may not be specific enough. A cross-reactive food may not need to be avoided if you’ve tolerated it before.

Negative tests can rule out an allergy. In the instance of positive tests for foods you’ve never eaten but are associated with allergens, an oral food challenge is the best way to determine the meal’s hazard.

How to test

An allergic reaction occurs every time the trigger food is eaten. Symptoms vary by person, and you may not always have the same ones. Skin, respiratory, GI, and CV systems can be affected by food allergies. It’s impossible to foresee the severity of a food allergy reaction, therefore all patients should be informed about anaphylaxis, a potentially lethal reaction treated with epinephrine (adrenaline).

While food allergies can develop at any age, most occur in childhood. If you suspect a food allergy, consult an allergist, who will collect your family and medical history, decide which tests to run, and determine if you have one.

To diagnose, allergists ask about medical history and symptoms. Be ready to answer:

After taking your history, an allergist may request skin testing and/or blood tests to detect food-specific IgE antibodies in your body.

Your allergist will diagnose you with these tests. A positive result doesn’t imply an allergy, but a negative result can rule one out.

Oral food challenges are sometimes recommended by allergists as the most accurate technique to diagnose food allergies. Under close medical supervision, a patient is fed tiny amounts of the suspected trigger meal in increasing dosages over time, then observed for a few hours to determine if a reaction occurs. When the patient’s history is vague or skin or blood tests are ambiguous, this test can help. Also used to assess if an allergy has been outgrown.

Because of the risk of a severe reaction, only experienced allergists at a doctor’s office or food challenge centre with emergency medication and equipment should do an oral food challenge.

Manage and treat

Managing a food allergy involves avoiding the offending food. Check food labels to see whether something you need to avoid has another name.

The Food Allergy Labeling and Consumer Protection Act of 2004 (FALCPA) requires U.S. food manufacturers to clearly label the presence of the eight most common allergens – milk, egg, wheat, soy, peanut, tree nut, fish, and crustacean shellfish – in their goods. The allergy must be listed even if it’s an addition or flavouring.

Some goods may be labelled with warnings such as “may contain,” “may contain,” “produced using shared equipment,” or “manufactured in a shared facility” There are no rules or regulations requiring advisory warnings or standards defining their meaning. If you have questions regarding safe foods, see an allergist.

The FALCPA labelling rules do not apply to items controlled by the U.S. Department of Agriculture (meat, poultry, and some egg products) and the Alcohol and Tobacco Tax and Trade Bureau (distilled spirits, wine and beer). The regulation does not apply to cosmetics, shampoos, and other beauty aids that contain tree nut extracts or wheat proteins.

It’s hard to avoid allergens. While labelling has helped, avoiding some foods can be difficult. A dietician or nutritionist may help. These food experts will offer recommendations for avoiding foods that trigger your allergies and guarantee you obtain all the nutrients you need if you omit specific items from your diet. Cookbooks and support groups for patients with specific allergies can also be helpful.

Food allergy sufferers ask if their illness is permanent. There’s no answer. Milk, eggs, wheat and soy allergies may fade with time, but peanut, tree nut, fish and shellfish sensitivities are usually lifelong.


Be careful eating out. Waiters (and sometimes kitchen personnel) may not know all menu ingredients. Depending on your sensitivity, just entering a kitchen or restaurant can trigger allergies.

Many websites offer “chef cards” that list your allergy and what you can’t eat. Always notify servers about allergies and ask to speak to the chef if feasible. Insist on clean surfaces, pans, pots, and utensils and ask the restaurant staff whether meals are safe for you.


The intensity of food allergy symptoms can range from moderate to life-threatening. Mild symptoms might abruptly turn into a life-threatening reaction called anaphylaxis, which can hamper breathing and lower blood pressure. This is why allergists don’t want to identify someone as “mildly” or “severely” food allergic. They can’t predict what the next reaction will be. In the U.S., food allergy causes the most anaphylaxis outside of hospitals.

Epinephrine (adrenaline) is the first-line treatment for anaphylaxis, which occurs when an allergen generates a chemical rush that can shock the body. Anaphylaxis can develop quickly and be lethal after allergen exposure.

Your allergist will prescribe an epinephrine auto-injector and instruct you how to use it if you have a food allergy. You should also be provided with a written treatment plan explaining your medications and when to use them. Check the expiration date of your auto-injector and ask your pharmacist about refill reminders.

A food allergy sufferer should always carry an auto-injector. Two doses should be supplied, as severe reactions can recur in 20% of people. There are no data to determine who may need a second dose of epinephrine, therefore this suggestion applies to all food allergy patients.

Use epinephrine immediately if you have shortness of breath, repetitive coughing, a weak pulse, hives, throat tightness, trouble breathing or swallowing, or a combination of symptoms from different body areas, such as hives, rashes or swelling on the skin coupled with vomiting, diarrhoea, or abdominal pain. It may take multiple doses. Call an ambulance (or have someone else do it) and tell the dispatcher epinephrine was given and more may be needed. You should go to the ER; hospital regulations on monitoring epinephrine patients vary.

If you’re unsure if a reaction justifies epinephrine, use it nevertheless; the advantages outweigh the risk that a dose may not have been necessary.

Epinephrine causes anxiety, restlessness, dizziness, and shakiness. Rarely, the medicine might cause irregular heart rate or rhythm, heart attack, high blood pressure, and fluid buildup in the lungs. Heart disease and diabetes may increase your risk for epinephrine side effects. Despite its risks, epinephrine is the best treatment for treating severe allergic responses.

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