Some people become ill when they come into contact with a substance that may have no effect on other people. Their illness is due to an allergy – an abnormal response by the immune system to a foreign invader. When a person’s immune system reacts abnormally to a substance that has no effect on most people, we say that the affected person has an “allergy” to the substance and that they are suffering from an allergic reaction.
An allergic reaction can show itself in different ways, such as sneezing, an itching or runny nose, breathing problems, swelling of the face (angiocdema) and the most serious form, anaphylaxis.
The substance that causes such a reaction is known as an allergen. Common examples of allergens that affect the lungs include pollens from grass and trees, house dust mite and animal fur.
Some people – between a quarter and a third of us – are more likely than others to have allergies of one kind or another. This tendency runs in families and is called “atopy”. However, not all the people who have this tendency will actually get allergy problems.
How The Body Responds To Allergens
Allergens, usually proteins, are seen by the body as “foreign” and the body’s natural response to anything foreign is to repel it.
The body makes antibodies to neutralize and repel die allergen. If you make die allergic type of antibodies (IgE), when allergens and antibodies meet up inside the body there’s quite an explosion, with the release of many chemicals that can irritate tissues and even cause disease and illness. An example would be histamine, which narrows the bronchial tubes and causes wheezing as in asthma.
The symptoms of an allergic disease simply depend on where this explosion happens. So if it’s in the skin, you’ll get a rash; if it’s in the nose, you’ll get itching and sneezing; if it’s in the lungs, you’ll get wheezing.
Very rarely, and for reasons we don’t understand, the body may see part of itself as the allergen and attack the thyroid gland or the joints or the pancreas and we then get thyroid disease, arthritis and diabetes respectively, which are called “autoimmune diseases”.
The Commonest Allergies
- Some allergies can cause problems all through the year; others only affect us at certain times. The most common cause of year- round allergy is the house dust mite these tiny mites, found in every home, feed off human skin scales, which we all shed naturally. House dust mites arc especially common in bedding, such as pillows and mattresses.
- Another common cause of year-round allergy is skin and fur from cats and dogs, horses and other animals.
Some people suffer from allergy because of substances at their place of work, such as certain kinds of dust.
Allergens that cause problems only at certain times of the year include pollen from trees (springtime), from grass (high summer), or from weeds (late summer). Some fungi produce mould spores that may cause allergy in late summer and autumn.
Some Allergic Illnesses
- By far the most common allergic illness in the UK is summer hay fever from grass pollen. Hay fever usually causes itching, sneezing and a ninny or blocked nose. Other problems can include sore eyes, an itchy palate (the roof of the mouth) and breathing problems.
- Allergy can often cause asthma, a common lung disease which can make breathing out difficult, and gives a tight feeling in the chest. Asthma affects people of any age, although it is most often found in the young and middle-aged. Asthma may be set off by a year-round allergen such as house dust mites, or by a seasonal one such as pollen.
- Some skin conditions are allergic in origin, e.g. contact dermatitis and drug rashes.
- The autoimmune group of allergic diseases is huge, affecting every organ in the body.
Symptoms of Allergies
Never assume you have an allergy and take unilateral action, such as embarking on an exclusion diet or putting your child on one – that can he dangerous.
Your family doctor may be able to tell straight away if you have an allergy. However, some allergies arc easier to diagnose than others. For example, if you have hay fever or asthma that gets worse in June and July, it is very likely that you arc allergic to grass pollen.
With other allergies, such as dust mite or animal fur, you may have to have special tests before the doctor can be sure what the problem is. If she thinks you might have a lung allergy, she may refer you an allergist or a lung specialist.
Can I Take Avoiding Action?
It is difficult to avoid pollens, the most common cause of allergic illness. It may help to wear sunglasses and to keep windows shut, especially when in cars and tall buildings. Avoid open grassy spaces, particularly during the evening or at night, when there is more pollen at ground level. A holiday by the sea or abroad during the peak pollen season may help.
If a bad allergic problem is caused by cats or dogs, then it is better not to keep such pets. Of course, most people would not want to get rid of a family friend, but when the time comes, you should think carefully before replacing your pet
In the meantime, it will help if the animal stays out of doors as much as possible and the house is kept very clean. Washing your cat or dog once a week is also an effective way of reducing allergen levels in the home, although it won’t make you very popular with your pet!
You can reduce house dust into problems by using special covers for mattresses, pillows and duvets. Clean the house often, as carefully as you can, and allow plenty of air in – this will help to reduce the dampness that house dust mites like. It will help if you have a good vacuum cleaner, fitted with a small pore-size filter.
Tests For Allergy
A skin prick test or patch test are the only true tests for an allergy. If you don’t have these tests done you can never be sure you actually have an allergy. Both are simple and painless procedures to find out if you’re allergic to anything.
- In a skin prick test, dilute solutions are made from extracts of allergens, such as pollen, dust, dander and food, that commonly cause allergic reactions. A drop of each solution is placed on the skin, which is then pricked with a needle. The skin is observed for a reaction, which usually occurs within 30 minutes of applying the solution. Antihistamines should not be taken on the day of the test because they may prevent any reaction.
NB An exclusion diet shouldn’t be undertaken unless you’ve had a skin prick lest done first in a proper allergy clinic attached to a hospital.
- Patch testing is carried out on people with contact dermatitis.
The test is performed by a dermatologist, to find out which substances provoke an allergic reaction in the skin. Possible allergens (substances that can cause an allergic reaction) are diluted and placed on small strips or disks. The test patches are then stuck to the skin using inert (non-allergenic) tape. After 48 hours, the patches are removed and the skin underneath them is examined. A red, inflamed area indicates a positive reaction to an allergen. The tested area is examined again two days later to check for delayed reactions.
Treatment of Allergies
- A skin prick or a patch test may be done to identify the allergen. In some cases, the allergen cannot be found.
- Nasal sprays containing decongestants can relieve symptoms but should not be used regularly.
- Oral antihistamines are often combined with decongestants to relieve inflammation and itching.
- Eyedrops may help relieve eye symptoms, a Rarely, if symptoms are severe, your doctor may prescribe an oral corticosteroid. a The most specific treatment is immunotherapy, in which you are injected with gradually increasing doses of allergen to desensitize the immune system. The treatment can take up to four years and is not always successful.