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What is an allergy?

An allergy is a disorder of the immune system which, causes an exaggerated response within the body when you come into contact with a foreign substance, that would be harmless in most people. The contact can be with your skin, mouth, gullet (oesophagus), stomach, intestine or with the lining of your lungs. Substances in the environment that cause the response are known as allergens and someone who suffers a response to a particular allergen is said to be allergic to it. If you are allergic to a particular allergen you may suffer from a mild cough or a sneeze attack, but for others the symptoms can be much more severe, and can even lead to death. Almost any substance can be an allergen for someone.

Allergies are generally the body’s way of eliminating something it considers unsuitable. Allergies are responsible for many illnesses, especially in young children. If you think you have an allergy, you must contact your doctor who will help you to control the symptoms.

What causes allergies?

An allergy occurs when the allergen in question e.g. pollen, triggers a reaction in the body of the individual. When the allergen comes into contact with the body, the immune system believes that the specific allergen is harmful and so produces an antibody called IgE (E-class Immunoglobin) to fight it. This antibody then triggers chemicals, including one called histamine to be released from cells (called mast cells) in our skin, lungs, nose or intestine, causing the various symptoms of an allergic reaction.

The most common allergens are as follows:

  • The house dust mite is one of the most common causes of allergies and no matter how clean your house every household will have them. The warmth and humidity in most homes is an ideal breeding environment for them, therefore our beds are a haven for them and a single mattress can contain up to 2 million mites. Mite allergy is caused by the mite faeces, which when inhaled cause breathing problems (asthma) or can irritate the skin on contact.
  • Pollen from grass, trees and weeds is the second most common cause of allergies. Pollen allergies are usually seasonal. This type of allergy is called hay fever.
  • The family pet is also a common cause of an allergy. The majority of U.K. households have a pet with 40% of asthmatic children being allergic to cats and/or dogs. It is usually the skin/fur (animal dander) which causes the problem. For more details on animal allergies click here.
  • Insects bites such as those from bees or wasps.
  • Foods and drinks, such as milk, eggs, fish, wheat, soy, citrus fruits, seafood and peanuts. Colourings and preservatives can also trigger attacks. For more information on food allergies click here.
  • Cosmetics, toiletries, jewellery and washing powders all contain common allergens. Symptoms are typically identified by an itchy, red rash.
  • Mould and mould fungus. Mould grows in damp conditions and is obvious in houses that have damp patches on the walls or black mould around window seals or bathrooms. Mould spores can also be found in the soil of house plants.
  • Latex and rubber.
  • Certain medicines and drugs, such as antibiotics and anaesthetics.

What symptoms are linked with an allergy?

There are many different types of allergies and the symptoms can vary according to what the allergen is, how severe the reactions and what part of the body is involved.

Common symptoms of an allergy may include:

  • Attacks of sneezing or a runny nose (usually key symptoms of an allergy).
  • Blocked nose and sinus pain.
  • Watery, itchy eyes.
  • Itchy, red rashes or inflamed skin (eczema or dermatitis).
  • Number of raised bumps or weals surrounded by red skin, which can be itchy. This is known as urticaria, hives or nettle rash. Urticaria can be caused by allergies to animals, foods, bee stings or medicines.
  • Coughing.
  • Swelling of the lips and tongue.
  • Diarrhoea.
  • Sickness and vomiting.
  • Itchy, sore throat.
  • Wheezing and shortness of breath (asthma attacks).
  • Anaphylaxis, the most extreme of allergic reactions.

How many people suffer from allergies in the U.K.?

The number of people with allergies has increased dramatically over the past 20 years:

  • 44% of adults now suffer from at least one allergy and almost half of suffers have more than 1 allergy.
  • 1 in 5 adults and as many as 2 in 5 children, suffer from hay fever. (Estimated 18 million in the U.K. are thought to be affected)
  • 1 in 11 children and 1 in 12 adults are currently receiving treatment for asthma.
  • It is estimated that up to 15 million people have eczema.

Why do people get allergies?

It is unknown exactly why people get allergies, some experts believe they could be hereditary. This is especially true for certain reactions such as, asthma, eczema and hay fever. If one or both parents have allergies there is a high chance the child will also have allergies. However, the child only inherits the likelihood of having allergies, not a particular allergy. A child is also more likely to develop allergies if exposed to passive smoking.

There has been a great amount of research done of late and many experts believe, that the increase in people developing allergies, could be due to the lifestyles many of us lead and the effect it has on our immune system. Another theory is the increased pollution from vehicle exhausts and other environmental pollutants.

How do I know if I have an allergy?

If you have experienced any of the symptoms mentioned above then you may have suffered an allergic reaction, if so you should seek you doctors advice. If you are not sure what caused your reaction you should try to write down the following:

  • When your reaction occurs, is it at any particular time of the day or year and how often?
  • Which part of the body is affected?
  • How severe are the symptoms?
  • Do you sneeze or wheeze when you clean the house?
  • Are there any remedies that improve your symptoms?
  • Is there anything that seems to make your symptoms worse?
  • Do your symptoms improve/worsen when at work/home/outdoors?
  • Is there a family history of allergies?
  • Have you eaten anything different?
  • Have you been in contact with any animals?

This will help your doctor identify the specific allergen. Finding out if you have a certain allergy and what the possible causes are, will help your doctor decide what treatment you may need or what you can do to help yourself. If you have had a severe allergic reaction you should seek medical advice immediately.

How are allergies diagnosed?

Firstly, your doctor will question you about your symptoms and when they usually occur. Instant advice will be on offer, but in many cases you may need to be referred to an N.H.S. allergy clinic. There are about 90 clinics in the U.K. and your doctor will provide details of these.

There are a number of tests that can detect whether your symptoms are due to an allergy. These tests will be able to identify the allergen(s) responsible, so if possible you can avoid them in the future. The type of test you are given will depend upon your symptoms and condition of your skin.

If you believe your allergy may be caused by food then you may need to do an elimination diet, for more information on this read the section ” How can I find out what foods I’m allergic to?” on the food allergies page.

As mentioned above, when you are exposed to an allergen, the immune system produces the IgE antibody. People who have an allergy to a substance will have raised levels of the IgE antibody, and it is this antibody that all the following tests look for.

Skin prick test

This test involves using a small needle to prick a drop of fluid containing a known allergen, just under the surface of the skin. The test is usually carried out on the skin on the inner forearm, although with young children it may be done on the back so they don’t have to see what is happening. The test may be uncomfortable but should not be painful.

A positive result to the skin prick test is indicated within minutes. The skin around the area pricked will become red and itchy and after about 20 minutes the area swells and a raised circle will appear, this is known as a weal. The larger the weal, the more likely that you are allergic. This blister like circle will fade within a few hours.

If your skin does not react in any way this will indicate a negative result.

20 – 25 allergens may be tested at one time or as few as 3 or 4.

Skin patch test

This test is performed if you have contact dermatitis (eczema) and involves solutions of common allergens being spread on to discs (made of special metals), 1 cm in diameter. The discs are then taped to your skin, usually on your back and left in place for 2 – 3 days. After this time the discs are removed and the surrounding skin is examined for any reactions. Like the skin prick test, if you develop a red, itchy area, it means the result is positive. This test is painless and very safe.

Blood tests

A blood test can be used to detect the presence of IgE antibodies in your blood. As with any blood test, a sample is taken and then sent to a specialist laboratory for what is known as a RAST (Radio Allergo-Sorbent Test). Unlike the skin test a blood test is very accurate, measuring the precise amount of allergy antibodies(IgE) in the blood. The test is graded on a scale of 0 – 6, with 6 being the highest level of antibodies and therefore producing the strongest allergic reaction.

Like skin testing, many allergens (over 400) can be tested from one blood sample. This test is particularly useful if you have eczema as the skin patch test can be uncomfortable. There is also a respiratory allergy screening test and a food allergy screening test, which can identify allergies to dairy products, wheat, fish, soya and nuts.

How are allergies treated?

Prevention is the key in allergy sufferers, so if you know you have an allergy to something you should make the effort to avoid or reduce contact with the specific allergen. To control allergy symptoms you should try the following tips:

  • Remove all carpets and switch to wooden floors, tiles or vinyl to reduce the presence of the house dust mite.
  • Vacuum soft furnishings frequently or switch to leather or vinyl sofas and chairs.
  • Keep your house well ventilated (open windows when cooking and bathing) to reduce humidity levels and prevent mould from forming.
  • Wash bedding weekly at a temperature of 60°c or above to kill off any allergens.
  • Buy special mattresses and pillow coverings that are resistant to the dust mite.
  • Regularly dust and vacuum your house to reduce the population of house dust mites. Ensure your vacuum cleaner has the British Allergy Foundation seal of approval to remove dust mites and cat and dog allergens.
  • Put your child’s soft toys in a bag in a freezer for at least 12 hours every month or wash them frequently at high temperatures to kill off dust mites.
  • Don’t buy pets but if you do have them, keep them outside and never allow them in a bedroom.
  • Use non-scented and hypoallergenic products.
  • Use gloves when handling chemicals, solvents and detergents.

There are also drugs available which can ease an allergic reaction. The most common drugs used for allergy symptoms are antihistamines and steroids, which come in the form of nasal sprays, creams or tablets. The exact treatment depends on the area of the body involved.

For specific treatments for different allergies please read their individual pages for more details.