Food allergy and food intolerance
When your immune system displays a significant adverse reaction to a specific protein found in food, this is known as a food allergy.
The severity of these reactions will vary from person to person, ranging from a mild skin rash right through to a life threatening anaphylactic shock which will require immediate medical attention.
Allergic reactions are made up of two key responses within the immune system, the first of which is the production of an antibody known as immunoglobulin E (IgE) which circulates within the blood stream, and the second of which is the mast cell, a cell which occurs in body tissue but which is especially common in sites of allergic reactions.
On this page
- Development of allergies
- Prevalence of allergies
- Anaphylactic shock
- Allergy testing
- Risk factors
- Food intolerance
Development of allergies
The development of an allergy occurs when the immune system overreacts to a foreign protein known as an allergen, which in this case is a particular type of food.
Interestingly, you won't experience an allergic response the very first time you eat a new type of food, and before a reaction occurs individuals who are predisposed to form IgE to foods will first have to be exposed to the food. At this stage, digestion of the food will trigger the production of large amount of IgE which will be released before attaching itself to the surface of mast cells.
Next time you expose yourself to this food, the body will produce a higher volume of the allergen which will interact with specific IgE on the surface of the mast cells, triggering the cells to release chemicals such as histamine.
The type of allergic reaction itself will be dependent upon the tissue in which they are released, for example, mast cells which release chemicals into the nose may result in the throat swelling and difficulty with breathing or swallowing, or affected cells in the gastrointestinal tract may cause pain in the abdomen or diarrhoea.
Often, food-allergy is confused with food intolerance, which though can make you feel unwell is generally not as harmful and will not pose the immediate danger of a severe allergic reaction to a certain food.
Common food allergies include fish, shellfish, dairy, soya, wheat, peanuts and tree nuts such as almonds, brazils, cashews and walnuts.
Generally food allergies are more common among young children than they are in adults, though many do outgrow them before they reach their teenage years. Though incidences are quite rare, some adults may develop a food allergy to something they were previously able to eat.
Prevalence of allergies
In 2008 the Food Standards Agency (FSA) reported that approximately 1-2% of adults and 5-8% of children are affected by a food allergy, though some researchers believe that the figure for adults may be slightly higher as some individuals mistakes an allergy(which involves the immune system) for an intolerance to certain foods (which does not involve the immune system).
As mentioned previously, allergies are far more common among children than they are among adults and with the exception of peanut allergies which are very persistent (a large number of children with this allergy will remain allergic for the rest of their life) a high percentage of children who do suffer from allergies will actually outgrow them before they reach school age.
Individuals whose allergies persist into adulthood, or those who only begin to develop an allergy in their adult years stand a higher risk of being affected indefinitely, and it is unlikely that they will outgrow them.
Symptoms of an allergy will usually occur within just a few minutes of exposure but in some cases onset can be delayed. Some of the most common symptoms include swelling of the face and lips, blotchy and itchy skin, nausea, abdominal pains and cramping, diarrhoea, wheezing and vomiting.
Unfortunately there is no known cure for food allergies and treatment will usually revolve around identifying food triggers and avoiding them.
In the event that an individual does accidentally consume a food to which they are allergic, there are certain medications that can be taken to relieve the symptoms, and in very severe cases such as anaphylaxis, immediate medical treatment will need to be sought.
Anaphylaxis, or anaphylactic shock is a very severe and potentially life threatening allergic reaction. It can affect many areas of the body but commonly affects airways, breathing and blood circulation, resulting in breathing difficulties, dizziness and severe swelling to certain areas of the body such as the lips and hands.
Individuals who have a history of anaphylaxis may carry an auto-injector of adrenaline, the anti-allergy medicine which is used to treat the reaction. This is usually injected to the thigh muscle for around 10 seconds.
Regardless of whether an individual does carry an auto-injector, anaphylaxis should always be treated as a medical emergency, and if you suspect that either yourself or someone else is experience a reaction then it is important that you contact the emergency services.
Though this reaction can be life threatening, if treated quickly and effectively most individuals will make a full recovery and will not experience long term complications or side effects.
If you believe you may be suffering from a food allergy then your first port of call should be your GP, who as well as taking a full and detailed medical history will also arrange any appropriate tests. Once the allergen's have been identified, your GP will then be able to recommend the appropriate treatment.
Tests may include the following:
If your GP or local surgery are unable to carry out an allergy test themselves then they may refer you to an allergy clinic for further assessment.
This involves a sample of your blood being taken before it is sent to a specialist laboratory for assessment. Experts will be looking out for the amount of immunoglobulin E antibodies (IgE) as these are what trigger the release of histamine when we are exposed to certain environmental food allergens.
Test results usually return graded, with grade 0 representing a negative reaction, through to grade 6 representing a strong positive reaction, depending on the level of the allergen's specific IgE antibody in the blood. The higher the grade, the higher the risk of an allergy to the allergen being tested.
Blood tests can also test for IgE to dust mites, pollens and pets as well as food and there are also specific tests for nut, seafood, antibiotics, stings, latex etc.
Patch testing is usually used to diagnose allergic reactions which occur on the surface of the skin. It can test for allergies to hair dyes, cosmetics, skin medications, etc and the test itself is performed by placing a sample of known contact chemical allergens onto the skin, underneath a special aluminium disc for 48 hours.
After a period of time any blistering or reddening of the skin will be assessed.
This test is one of the most popular of the food allergy tests and is extremely accurate. The procedure itself involves a small needle, or lancet, being used to scratch the very surface of the skin through a tiny droplet of a fluid which contains a known allergen. Clinics will often use purified liquid forms of allergens but in some cases you may be required to bring a fresh sample.
A positive reaction is indicated when the skin surrounding the needle prick becomes red, itchy and slightly swollen. This effect is known as a wheal and it will usually develop to its maximum size within around 20 minutes and should fade within an hour and generally the larger the wheal, the more likely you are to be allergic.
Though this test can help to identify how sensitive you are to an allergen, what it can't do is predict how you will react to it in the event you are exposed, nor can provide a full proof diagnosis. GPs will see if your test results correlate with your symptoms in order to reach a diagnosis.
According to NHS information on food allergies, the number of cases has increased dramatically during the past two decades, with the number of children who are admitted to hospital for anaphylaxis as a result of a food allergy rising by 700% since 1990.
Though the reason for the sharp increase is unknown, as is the exact reason that IgE antibodies react against certain food proteins, there are a number of known factors which are thought to increase the likelihood of an individual being affected by a food allergy:
Those who are affected by other allergies from a young age, such as atopic dermatitis, stand an increased risk of developing a food allergy.
A significant increase in the number of food allergy cases during the past two decades has led some experts to believe that changes to the western diet could be partly responsible.
Having a family member who is affected with an allergic disease such as eczema or a food allergy puts individuals at a higher risk of developing a food allergy themselves.
Though any food could cause an allergic reaction, there are certain foods which seem to be more responsible for the development of allergies than others. In children, eggs, milk, peanuts, soya and wheat are the most common causes of allergic reaction, and in adults it is tree nuts, shellfish, fish and peanuts.
A food intolerance is a response in the digestive system as opposed to an immune system response, and occurs when the digestive system is unable to digest of break down the food properly.
For example, among the most common food intolerances is lactose intolerance, which can be found in milk and other dairy products. The intolerance is caused by an inability to digest the sugar lactose present in cow's milk and this is as a result of a lack of the sugar-digesting enzyme lactase in the intestine.
Food intolerance reactions tend to have a slower onset than allergic reactions, are often dose related and are not usually life threatening.
Common symptoms of food intolerance include the following:
- stomach pain
Prevalence of intolerances
Food intolerances are far more common than food allergies, and at some point during our lives it is likely that we will all experience an unwanted reaction to something we have eaten.
How do I know if I have a food intolerance?
Similarly to that of food allergies, there are many tests which can be performed which will help to establish any food intolerances.
Alongside tests, another popular method is a restriction/elimination diet. These diets involve eating only a limited number of foods which are unlikely to provoke an adverse reaction for a period of time, after which other foods will slowly begin to be reintroduced so that the offending food can be identified. Restriction diets should only be done under the supervision of a dietician or medical professional.
If you do suspect you have a food intolerance and are considering visiting your healthcare provider, it is always a good idea to take a food diary along with you which details what you have eaten during the past few weeks and any symptoms you have experienced. This diary should be as in depth as possible, with any mealtimes, drinks, snacks, medication and supplements recorded along with a description of symptoms, their intensity and when they occurred. All of this information will help your dietician, GP or health care provider to look for any patterns and identify any potential suspects.
Types of food intolerance
As mentioned previously, any type of food can potentially cause an adverse reaction but there are some foods which more commonly produce a reaction than others.
As well as lactose intolerance, individuals may also experience gluten intolerance, wheat intolerance and intolerance to some naturally occurring food compounds such as caffeine, or those found in red wine and cheese, both of which are renowned for triggering migraines and headaches in some people.
Coeliac disease, which is frequently and incorrectly referred to as an intolerance to gluten, is actually an autoimmune disease which causes the body to produce antibodies which attack its own tissue.
Individuals affected by coeliac disease will trigger a series of symptoms if they consume foods which contain gluten such as wheat, rye and barley. Cereals which contain gluten are also used in numerous different foods such as bread and pasta, and the same goes for wheat ingredients which can be found in some sausages, burgers, a variety of sauces and some alcoholic drinks which contain barley.
The condition may eventually cause damage to the lining of the small intestine, preventing it from absorbing the goodness from foods. The damage caused is usually a reaction to eating gluten and symptoms vary so greatly from person to person that often the condition can go undiagnosed for a period of time. Gastrointestinal symptoms can include abdominal pain, bloating, indigestion, constipation or diarrhoea, nausea, and unexplained weight loss.
In addition to this, because the condition prevents the intestines from absorbing vitamins and minerals which are essential for optimum well-being, sufferers may being to find that they bruise very easily, feel anxious or depressed and may experience fatigue, hair loss, missed periods, muscle cramps and pains, nosebleeds and even seizures.
Though coeliac disease can't be cured, if individuals take up a lifelong gluten free diet then symptoms will eventually go away and the lining of the intestines will heal.
There are plenty of specialist food ranges available which are designed for individuals who do have an intolerance. Most big supermarkets now carry a wheat-free and gluten-free free range as well as lots of dairy substitutes for those who are lactose intolerant.
How can a nutritionist help me?
If you are suffering from a range of symptoms which you believe could be caused by a food allergy or intolerance, then a qualified nutritionist specialising in this area could help you to identify what foods may be causing the issue and will then discuss with you what they consider to be the best way forward.
A food intolerance test will not necessarily be the best option for you and this is something which can be discussed during your initial consultation. After your nutritionist has gathered all of the information they need about your eating habits, symptoms, overall health and well-being etc, they can then move on to creating a personalised food intolerance or allergy diet so that symptoms and side effects are minimised and your health and well-being is optimised.
This may involve removing certain foods from your diet, and if this is the case then alternatives will be recommended so that plenty of food choices remain.
Many individuals who have previously suffered from food intolerance or mild allergies, find that their symptoms improve after having been on a personally tailored and monitored diet.
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