Food Allergies Causes, Types, Symptoms, Diagnosis, Treatment, Prevention, Home Remedies

Food Allergies Causes, Types, Symptoms, Diagnosis, Treatment, Prevention, Home Remedies


What is a food allergy?


A food allergy occurs when the immune system responds defensively to a specific food protein that is not harmful to the body. When that food is first eaten, the immune system responds by creating specific IgE antibodies. When the food is eaten again, the IgE antibodies go into action, releasing large amounts of histamines, which work to expel the food protein from the body. Histamines can affect the respiratory system, gastrointestinal tract, skin, and cardiovascular system.

Food Allergies Causes, Types, Symptoms, Diagnosis, Treatment, Prevention, Home Remedies

In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis.

Food allergy affects an estimated 6 to 8 percent of children under age 5, and about 3 to 4 percent of adults. While there's no cure, some children outgrow their food allergy as they get older. It's easy to confuse a food allergy with a much more common reaction known as food intolerance. While bothersome, food intolerance is a less serious condition that does not involve the immune system.

How do allergic reactions to food occur? Causes of Food Allergies


The allergens in food are those components that are responsible for inciting an allergic reaction. They are proteins that usually resist the heat of cooking, the acid in the stomach, and the intestinal digestive enzymes. As a result, the allergens survive to cross the gastrointestinal lining, enter the bloodstream, and go to target organs, causing allergic reactions throughout the body. The mechanism of food allergy involves the immune system and heredity.

Immune system


An allergic reaction to food involves two components of the immune system. One component is a type of protein, an allergy antibody called immunoglobulin E (IgE), which circulates through the blood. The other is the mast cell, a specialized cell that stores up histamine and is found in all tissues of the body. The mast cell is particularly found in areas of the body that are typically involved in allergic reactions, including the nose and throat, lungs, skin, and gastrointestinal tract.

Heredity


The tendency of an individual to produce IgE against something seemingly as innocuous as food appears to be inherited. Generally, people with allergies come from families in which allergies are common -- not necessarily to food but perhaps allergies to pollen, fur, feathers, or drugs. Thus, a person with two allergic parents is more likely to develop food allergies than someone with one allergic parent.

Mechanism


Food allergy is a hypersensitivity reaction, meaning that before an allergic reaction to an allergen in food can occur, a person needs to have been exposed previously, or "sensitized," to the food. At the initial exposure, the allergen stimulates lymphocytes (specialized white blood cells) to produce the IgE antibody that is specific for the allergen. This IgE then is released and attaches to the surface of the mast cells in different tissues of the body. The next time the person eats that particular food, its allergen hones in on the specific IgE antibody on the surface of the mast cells and prompts the cells to release chemicals such as histamine. Depending upon the tissue in which they are released, these chemicals cause the various symptoms of food allergy.

Common food allergies


In children, the foods that most commonly cause an allergic reaction are:


  • eggs
  • milk: if a child has an allergy to cow's milk, they will also be likely to be allergic to all types of milk, such as goat’s milk, as well as infants' and follow-on formula milk
  • soya
  • wheat
  • peanuts


In adults, the foods that most commonly cause an allergic reaction are:


  • some types of fruit such as apples, pears,
  • kiwi fruit and peaches
  • some types of vegetables such as potatoes, carrots, celery and parsnip
  • crustaceans (shellfish), such as crab, lobster and prawns
  • tree nuts, such as walnuts, brazil nuts, almonds and pistachios
  • peanuts
  • fish

However, potentially any type of food can cause an allergy.

Allergic reactions have been reported in association with:


  • celery or celeriac: this can sometimes cause anaphylactic shock
  • gluten: a type of protein found in cereals
  • mustard
  • sesame seeds
  • fruit and vegetables: usually only cause symptoms affecting the mouth, lips and throat (oral allergy syndrome)
  • pine nuts (a type of seed)
  • meat: some people are allergic to just one meat, while others are allergic to a range of meats. A common symptom is skin irritation.

Food intolerance and other reactions


There are a number of reactions to food that cause similar symptoms to a food allergy. Depending on the type of food intolerance you have, you may be able to eat small amounts of problem foods without a reaction. By contrast, if you have a true food allergy, even a tiny amount of food may trigger an allergic reaction. Because a food intolerance may involve some of the same signs and symptoms as a food allergy does — such as nausea, vomiting, cramping and diarrhea — people may confuse the two.

One of the tricky aspects of diagnosing food intolerance is that some people are sensitive not to the food itself but to a substance or ingredient used in the preparation of the food.

Common conditions that can cause symptoms mistaken for a food allergy include:

Absence of an enzyme needed to fully digest a food


You may not have adequate amounts of some enzymes needed to digest certain foods. Insufficient quantities of the enzyme lactase, for example, reduces your ability to digest lactose, the main sugar in milk products. Lactose intolerance can cause bloating, cramping, diarrhea and excess gas.

Food poisoning


Sometimes food poisoning can mimic an allergic reaction. Bacteria in spoiled tuna and other fish also can make a toxin that triggers harmful reactions.

Sensitivity to food additives


Some people have digestive reactions and other symptoms after eating certain food additives. For example, sulfites used to preserve dried fruit, canned goods and wine can trigger asthma attacks in sensitive people. Other food additives that could trigger severe reactions include monosodium glutamate (MSG), artificial sweeteners and food colorings.

Recurring stress or psychological factors


Sometimes the mere thought of a food may make you sick. The reason is not fully understood.

Celiac disease


While celiac disease is sometimes referred to as a gluten allergy, it isn't a true food allergy. Like a food allergy, it does involve an immune system response, but it's a unique immune system reaction that's more complex than a simple food allergy. This chronic digestive condition is triggered by eating gluten, a protein found in bread, pasta, cookies, and many other foods containing wheat, barley or rye. If you have celiac disease and eat foods containing gluten, an immune reaction occurs that causes damage to the surface of your small intestine, leading to an inability to absorb certain nutrients.

Risk factors of Food Allergies


Family history


You're at increased risk of food allergies if asthma, eczema, hives or allergies, such as hay fever, are common in your family.

A past food allergy


Children may outgrow a food allergy, but in some cases it returns later in life.

Other allergies


If you're already allergic to one food, you may be at increased risk of becoming allergic to another. Likewise, if you have other types of allergic reactions, such as hay fever or eczema, your risk of having a food allergy is greater.

Age


Food allergies are most common in children, especially toddlers and infants. As you grow older, your digestive system matures and your body is less likely to absorb food or food components that trigger allergies. Fortunately, children typically outgrow allergies to milk, soy, wheat and eggs. Severe allergies and allergies to nuts and shellfish are more likely to be lifelong.

Asthma


Asthma and food allergy commonly occur together. When they do, both food allergy and asthma symptoms are more likely to be severe.

Factors that may increase your risk of developing an anaphylactic reaction include:


  • Having a history of asthma
  • Being a teenager or younger
  • Waiting to treat your food allergy symptoms with epinephrine
  • Not having hives or other skin symptoms

Symptoms of a food allergy 


Some food allergies cause immediate symptoms whereas in others it takes much longer for symptoms to develop.

The most common type of allergic reaction to food is known as an IgE-mediated food allergy.

In this type of allergy the symptoms develop very quickly after eating the allergy-causing food (the allergen); typically within a few minutes or in some cases, seconds.

Food Allergies Symptoms include:


  • a raised red itchy skin rash (urticaria), which can affect just one part of the body, or alternatively, spread across the entire body – in some cases the skin can turn red and itchy but there is no raised rash
  • swelling of the face, around the eyes, lips, tongue or the roof of the mouth (angioedema)
  • feeling of narrowing in throat
  • change in voice (croaky or hoarse) due to swelling in voicebox
  • feeling dizzy and lightheaded
  • feeling sick
  • being sick
  • abdominal pain and spasms
  • diarrhoea
  • cold-like symptoms, such as sneezing, runny nose and nasal congestion
  • redness and irritation of the eyes (allergic conjunctivitis)
  • coughing 
  • chest tightness
  • wheezing or shortness of breath
In some cases a severe food allergy (anaphylaxis) can be triggered after eating a certain food and then going on to exercise vigorously. This is known as food-dependent exercise-induced anaphylaxis.

A less common type of allergic reaction is known as an non IgE-mediated food allergy. In this type of allergy the symptoms take much longer to develop after eating the allergen; usually several hours or in some cases days.

Some symptoms match what you would expect to see in an allergic reaction, such as:


  • redness and itchiness of the skin (although not necessarily raised)
  • the skin becomes itchy, red, dry and cracked (atopic eczema) 

Other symptoms can be much less obvious and easily mistaken as being caused by something other than an allergy. They include:

Exercise-induced food allergy


Some people have an allergic reaction to a food triggered by exercise. Eating certain foods may cause you to feel itchy and lightheaded soon after you start exercising. In serious cases, an exercise-induced food allergy can cause reactions such as hives or anaphylaxis. Not eating for a couple of hours before exercising and avoiding certain foods may help prevent this problem.

Pollen-food allergy syndrome


In many people who have hay fever, fresh fruits and vegetables and certain nuts and spices can trigger an allergic reaction that causes the mouth to tingle or itch. In some people, pollen-food allergy syndrome — sometimes called oral allergy syndrome — can cause swelling of the throat or even anaphylaxis. This is an example of cross-reactivity. Proteins in fruits and vegetables cause the reaction because they're similar to those allergy-causing proteins found in certain pollens. For example, if you're allergic to ragweed, you may also react to melons; if you're allergic to birch pollen, you may also react to apples. Cooking fruits and vegetables can help you avoid this reaction. Most cooked fruits and vegetables generally don't cause cross-reactive oral allergy symptoms.

Mixed reaction


Some children can have a mixed reaction where they experience both "IgE" symptoms, such as swelling, and "non-IgE" symptoms such as constipation.

This often happens to children who have a milk allergy.

Anaphylaxis


The symptoms of a severe anaphylactic reaction usually develop within a few minutes to an hour after exposure. They can be sudden and rapidly worsen.

Initial symptoms of anaphylaxis are often the same as above and can lead to:
  • a rapid heartbeat (tachycardia)
  • increasing breathing difficulties due to swelling and tightening of your neck
  • a sudden intense feeling of apprehension and fear (this has been described as a "sense of impending doom")
  • a sharp and sudden drop in your blood pressure, which can make you feel light-headed and confused
  • unconsciousness

When to see a doctor


See a doctor or allergist if you have food allergy symptoms shortly after eating. If possible, see your doctor when the allergic reaction is occurring. This will help your doctor make a diagnosis.

Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as:

  • Constriction of airways that makes it difficult to breathe
  • Shock, with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness or lightheadedness

How are food allergies diagnosed?


Your doctor can perform a skin test to determine which substances cause a reaction. The skin test involves applying a small amount of an allergen (allergy-causing substance) and then making either a tiny scratch or small prick with a needle in your arm or back. The scratches that become red and itchy indicate which substances trigger a defensive response by your immune system.

Your doctor might also do a radioallergosorbent blood test (RAST) to check the number of antibodies produced by the immune system. Elevated levels of certain antibodies can identify particular food allergies. Also, if you maintain a food diary, your doctor will have a much better starting point when determining your allergy-triggering foods.

How are food allergies treated?


The best way to cope with a food allergy is to strictly avoid the foods that cause a reaction. Mild reactions often will subside without treatment. For rashes, skin creams might ease discomfort, while antihistamines will help reduce itching, congestion, and other symptoms. For more serious reactions, corticosteroids such as prednisone will help to reduce swelling. In life-threatening situations, an epinephrine (Adrenalin®) injection immediately begins reversing symptoms and is the only effective treatment option.

Antihistamines


Antihistamines work by blocking the effects of histamine, a protein responsible for most of the symptoms of an allergic reaction.

Many antihistamines are available from your pharmacist without prescription so it may be a good idea to stock up in case of an emergency.

Some antihistamines, such as alimemazine and promethazine, aren't suitable for children under two years old. Therefore seek advice from your GP if you have a younger child with a food allergy about what types of antihistamines may be suitable.

Avoid drinking alcohol after taking an antihistamine as this can make you feel drowsy.

Adrenaline


Adrenaline works by narrowing the blood vessels to counteract the effects of low blood pressure, and by opening up the airways to help ease breathing difficulties.

If your child’s, or your own allergies, are thought have a potential risk of anaphylaxis or has had a previous episode of anaphylaxis, you will be given an auto-injector of adrenaline to use in case of emergencies.

Carefully read the manufacturer’s instructions that come with the auto-injector and when your child is old enough, train them how to use it (see below).

Experimental treatments


While there's ongoing research to find better treatments to reduce food allergy symptoms and prevent allergy attacks, there isn't any proven treatment that can prevent or completely relieve symptoms. Unfortunately allergy shots (immunotherapy), a series of injections used to reduce the effect of other allergies such as hay fever, aren't effective for treating food allergies. Two treatments that have shown some promise are:

Anti-IgE therapy. The medication omalizumab (Xolair) interferes with the body's ability to use IgE. The drug is currently being studied for treatment of allergic asthma and food allergies. However, this treatment is still considered experimental and more research needs to be done on the drug's long-term safety. It has been associated with a potential increased risk of anaphylaxis.

Oral immunotherapy. Researchers have been studying the use of oral immunotherapy (OIT) as a treatment for food allergy. Small doses of the food you're allergic to are swallowed or placed under your tongue (sublingual). The dose of the allergy-provoking food is gradually increased. Initial results look promising, even in people with peanut allergy. But, more research needs to be done to ensure that this treatment is safe.

Prevention for Food Allergies


The best way to prevent an allergic reaction is to know and avoid foods that cause signs and symptoms. For some people, this is a mere inconvenience, but others find it a greater hardship. Also some foods — when used as ingredients in certain dishes — may be well hidden. This is especially true in restaurants and in other social settings.

If you know you have a food allergy, follow these steps:


Know what you're eating and drinking. Be sure to read food labels carefully.

If you have already had a severe reaction, wear a medical alert bracelet or necklace that lets others know that you have a food allergy in case you have a reaction and you're unable to communicate.

Talk with your doctor about prescribing emergency epinephrine. You may need to carry an epinephrine autoinjector (EpiPen, EpiPen Jr, Twinject) if you're at risk of a severe allergic reaction.

Be careful at restaurants. Be certain your server or chef is aware that you absolutely can't eat the food you're allergic to, and you need to be completely certain that the meal you order doesn't contain it. Also, make sure food isn't prepared on surfaces or in pans that contained any of the food you're allergic to. Don't be reluctant to make your needs known. Restaurant staff members are usually more than happy to help when they clearly understand your request.

If your child has a food allergy, take these precautions to ensure his or her safety:


Notify key people that your child has a food allergy. Talk with child care providers, school personnel, parents of your child's friends and other adults who regularly interact with your child. Emphasize that an allergic reaction can be life-threatening and requires immediate action. Make sure that your child also knows to ask for help right away if he or she reacts to food.

Explain food allergy symptoms. Teach the adults who spend time with your child how to recognize signs and symptoms of an allergic reaction.

Write an action plan. Your plan should describe how to care for your child when he or she has an allergic reaction to food. Provide a copy of the plan to your child's school nurse and others who care for and supervise your child.

Have your child wear a medical alert bracelet or necklace. This alert lists your child's allergy symptoms and explains how others can provide first aid in an emergency.

Home remedies for Food Allergies


Don't assume


Always read food labels to make sure they don't contain an ingredient you're allergic to. Even if you think you know what's in a food, check the label. Ingredients sometimes change. Food labels are required to clearly list whether they contain any common food allergens. Read food labels carefully to avoid these top eight sources of food allergens: milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat.

When in doubt, say no thanks


At restaurants and social gatherings, you're always taking a risk that you might eat a food you're allergic to. Many people don't understand the seriousness of an allergic food reaction and may not realize that a tiny amount of a food can cause a severe reaction in some people. If you have any suspicion at all that a food may contain something you're allergic to, steer clear.

Involve caregivers


If your child has a food allergy, enlist the help of relatives, baby sitters, teachers and other caregivers. Make sure they understand how important it is for your child to avoid the allergy-causing food and that they know what to do in an emergency. It's also important to let caregivers know what steps they can take to prevent a reaction in the first place, such as careful hand-washing, and cleaning any surfaces that might have come in contact with the allergy-causing food.

Living with food allergies


Once you and your doctor have determined which foods you should avoid, it is important that you maintain a healthy, nutritious diet. Ask your doctor to recommend foods that will provide you with the necessary nutrition. You should also be aware of the ingredients in processed foods.

Be sure to read labels. For instance, did you know that vitamins, processed meats, and packaged dessert mixes are often made with milk or dairy ingredients? A registered dietitian can provide tips on label reading, as well as a list of ingredients to avoid so that all sources of the food allergen are avoided.

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