Allergy and Asthma
	(Including: Indoor allergens & Pollen and asthma in South Africa)

Introduction

Allergy is a serious and increasing problem but our understanding of these problems has increased enormously over the past 20 years. Therefore one can be very optimistic about the outlook for allergy sufferers these days and there is no need to be over-concerned if you have an allergy.

With allergy we experience an altered reactivity. Allergy is one of a series of immunological defences that our body has to protect us against bacteria, viruses or parasites. Unfortunately, this protection sometimes harms us as well. Then we get allergies.

Allergens are the substances that may cause these reactions. Examples are pollens from trees, grasses and weeds, animal allergens from cats or dogs, house-dust and especially house-dust mites, insects parts and insect stings, food additives, fungal spores and even certain medicines such as aspirin or penicillin.

We make contact with these allergens by breathing, eating and touching them. Once in the body the allergens encounter mast cells and other specialised cells. These cells belong to a group of cells that act as soldiers of the body's immune system. They line the areas of our bodies that are in contact with the outside world, the skin, nose, lungs and digestive systems.

The surface of mast cells are covered with specific antibodies called IgE (Immunoglobulin E). When a mast cell encounters an allergen such as house-dust mite and has the specific IgE for this allergen on its surface, a series of complex biochemical reactions occur within the mast cell. This will result in the secretion of granules containing chemicals such as histamine. These chemicals known as "mediators" are the substances which cause allergic damage, especially swelling and inflammation.

It is now recognised that in the majority of asthma sufferers, certainly in virtually all children, the inflammation of the lining membrane of the airways is caused by an allergic reaction. Other factors such as viral infections, exposure to pollutants, cigarette smoke, mist and cold air and certain forms of exercise may also provoke the same reaction and result in airway inflammation. Certain occupations carry an increased risk for adult asthmatics. These include bakers, veterinary surgeons, spray painters and wood- workers.

How is the diagnosis of allergy made?

There are several ways to determine whether a person with asthma is allergic. This is usually through the doctor taking a careful history, conducting a screening test (Phadiatop) and then doing skin tests or blood tests (RAST) to find out which allergens are affecting the sufferer.

What can be done about allergies and asthma?

There are a number of approaches to the treatment of asthma. The most important one aims at the complete removal of the allergen where at all possible. The elimination of allergy-producing house-dust mites, the removal of a dog or cat or a feather pillow are simple examples of removing the offending problem. Some younger children may benefit from the avoidance of certain foods such as milk. All asthmatics should avoid known preservatives such as sulphur dioxide.

Your doctor will be able to provide you with excellent advice about avoidance programmes. Printed guidelines are widely available through the Allergy Society of South Africa and you should request these from your doctor. The more knowledge you have about avoidance programmes the better the outlook will be for the treatment of your asthma. Certain occupations carrying a high-risk of allergic sensitisation, should be recommended for young asthmatics about to embark on a career.

In addition to avoidance procedures there is a wide-range of highly effective medicines to treat all grades of asthma. In the vast majority of cases there is absolutely no reason why people who have asthma should not be able to lead a normal, active and happy life these days.

INDOOR ALLERGENS

The most common indoor allergens in South Africa are animal danders, feathers, moulds, house-dust mites and cockroaches.

• Animal danders
  These are minute portions of saliva, skin or hair of dogs, cats, rabbits, hamsters or even mice! They are harmless in themselves but, unfortunately, they are potent allergens and can provoke allergic sensitisation.

  Other sensitised, any contact with an allergen will result in an allergic reaction, asthma or hay fever. If you can avoid contact you will get better. If you are allergic to animals, you should not own them. Cat fur, in particular, is very potent, possibly because cats lick their fur making double trouble. Pets may already be part of your family, so you must try and keep them out doors. In particular, keep them out of your bedroom and carpeted, upholstered living rooms where their hair and fur may collect in large amounts. See that they are bathed and brushed regularly, even the cat! Be careful when you visit friends who own pets - always take your medication.

• Feathers
  These cause allergies, even if contained in a pillow. You can easily avoid feathers in the home. Some special pillow and duvet covers are available.
• Mould
  These flourish in dark, damp places. They reproduce by forming tiny spores, which like animal danders, are also potent allergens. You will often see mould growing in showers and dank basements, but look carefully and you may find them in pot plant soil, in mattresses, behind cupboards and under carpets laid on concrete floors. Mould should be removed as far as possible and clothes and cupboards must be aired. Ventilation and light should be increased and humidity decreased when possible. Our South African sunshine helps us do just this.
• House dust mites
  These are microscopic busy innocuous creatures which live mainly in our mattresses, bedding and in carpet dust. They love warm, humid settings. Hundreds can be found in just a pinch of house dust. They harmlessly feed off the scales of our skin which we shed continuously. However, not only are their body parts strong allergens, their minute droppings can also cause allergic sensitisation. Large amounts can cause serious allergic attacks. Mites grow more readily when humidity is high, so larger amounts are found in coastal regions and houses situated in humid areas. House dust mite sensitivity is very high in these areas, but even in apparently less favourable conditions, mites are now surviving and growing.

  If you are allergic to house dust mites you can ask your doctor about testing for antigen in your home. We know that we can decrease numbers by regular vacuuming, cleaning with damp cloths and covering mattresses with a mite-proof lining. Airing linen is beneficial as drying and heating kills the mites. Washing sheets and bedding in very hot water also kills them. Fluffy toys and deep carpets are dust havens for mites that can be avoided. Special mite sprays are available and may complement the measures outlined above. They should not be used as a first line approach.

• Cockroaches
  Did you know that cockroach eggs, droppings and bodies are all common allergens? If you live in a house where cockroaches are found, they must be exterminated but this can be very difficult when an allergic person lives in an infested building.

POLLEN

South Africa has one of the largest floral kingdoms in the world, with over 8000 species of flora found in the Cape Peninsula alone. In Southern Africa there are 947 indigenous grass species and 115 naturalised grass species. All of these produce pollen at different times of the year and the levels of pollen in the atmosphere are available, depending on the season, the presence of wind or thermal currents.

Although abundant pollen is produced everyday, not all pollens cause allergic symptoms. The pollens that are wind dispersed are often allergenic whereas the sticky heavier pollens, produced by brightly coloured flowers and dispersed by insects or birds, are often not allergic.

Are pollen grains an important cause of asthma?

Viral infections are the commonest precipitants of acute asthmatic attacks in allergic people. However, exposure to pollens in pollen sensitive individuals increases the irritability of the airways of asthmatics to other triggers of asthma, e.g. cold air, exercise and emotional stimuli. In some patients, direct exposure to pollens alone will trigger an asthma attack. These patients typically present with seasonal asthma, particularly in spring, when a particular grass, weed or tree is flowering.

Which pollens are important?

The grass pollens are by far the most abundant of the pollens and because they are small they are able to be inhaled and enter the airways of the lungs. Rye grass, Bermuda grass, Kikuyu grass and Eragostis pollens are abundant, but because the grass flowering seasons in South Africa are very long (from August to April) well defined seasonal symptoms are not always recognised.
Tree pollens, by contrast, are released for short periods (usually only a few weeks in the year in early Spring i.e. August-September) and typically cause well defined seasonal asthma. Important tree pollens include Acacia, Willow, Oak, Plane and Poplar.

How does one test for pollen allergy?

Pollen allergy can be diagnosed by either skin prick tests or by laboratory tests on a sample of the patients blood. These tests are very reliable for the identification of the grass, tree or weed sensitive patient. It is important, however, that antihistamines should be discontinued a few days before skin tests are performed since antihistamines can block the reaction of skin tests. Cross reactivity to grasses occurs and means that when you react to one grass you often react to other grasses.

What is the treatment for pollen allergy in asthmatics?

Avoidance is the most effective treatment strategy for pollen allergy. Pollen allergens are difficult to avoid completely, but simple measures such as keeping windows closed, avoiding grass cuttings and avoiding direct exposure to flowering trees or flowers should be attempted.

Pollen exposure is an uncommon precipitant of an acute asthmatic attack, but if asthma is induced, the treatment is the same as for any other asthma attack.

Desensitisation to pollen allergens is safe, successful and recommended if symptoms are predominantly those of hay fever. Pollen desensitisation for asthmatic subjects is a risky procedure and could induce a severe asthmatic attack. It is therefore not recommended as a routine treatment as present, although further research studies on the effectiveness and safety of this procedure are currently in progress.

Written by: Professor Eugene Weinberg, Dr Gloria David, Professor Paul Potter