Inhalent sensitivities - Part 1

allergens

This group includes pollens, moulds, animal dander and housedust mites.

Housedust Mites are probably the most important inhaled allergen; reducing exposure to them is the most fundamental aspect of allergen avoidance. They are found in large numbers in most houses in the UK; they require a food source (shed skin scales), warmth, and humidity to survive.

Skin scales are found in abundance in bedding, soft furnishings and carpets. Each night we warm up our beds as we sleep, shed skin and provide moisture through perspiration and breathing (roughly a pint per person per night); therefore high levels of mites are found in bedclothes, mattresses and pillows. Each mite passes very small faecal pellets (about 30 microns); these are extremely dry as the housedust mite needs to conserve as much moisture as possible. These pellets fragment easily into particles, which become airborne very easily, and remain airborne for many hours. They are of a size that our defences find most difficult to keep out of our airways, and they are therefore easily inhaled. As they land on the surface of the airways they set up an immune response; because they will act as a repeated stimulus to the immune system, in the susceptible patient allergy may well develop.

Housedust mite exposure should be reduced even if you do not think it is a particular problem – almost every allergic patient is allergic to them, and this puts a constant ‘load’ on the immune system.

There are several ways of approaching the control of housedust mite exposure:-

• The most important area to tackle is the bed. Wash bedding regularly. Mites in bedclothes will be killed if you can hot wash them (60oC and above). Although normal cool washing does not kill mites, it does wash out the allergic component of the pellets that causes the problem, and it will be some time before the levels rise again. Pillows are supposed to be washable but in practice it can be difficult getting them dry, and mattresses can’t be washed at all. Therefore pillows and mattresses hold high levels of mites and every night their pellets are breathed in as we sleep. They should be covered with a special ‘allergy’ breathable barrier cover if possible. The duvet should also be covered in the same way unless it is washable and is regularly washed. Mattresses on slatted bases, which allow good air circulation, are an advantage if possible.

• Kill them with high temperature steam cleaning of carpets, mattresses etc (high-temp steam leaves things dry rather than wet); or by freezing (e.g. pillows, soft toys).
• Increase ventilation to lower humidity (i.e. have windows open as much as possible). One of the reasons for the increase in housedust mite problems in recent decades is poor ventilation leading to higher humidity, which encourages mite growth. Reducing humidity levels kill mites, and as it also controls mould growth and reduces indoor air pollution (often worse than outdoor pollution).
• The best option is a good air filter (and a dehumidifier if the house is particularly damp). There are many air filters on the market that will trap larger particles such as whole pollen grains and mite pellets, but fragmented pellets and pollens, and some mould spores, are of a size (up to one micron) which most easily get through our defences. Up to 95% of the airborne particles in a room will be of this size, and they are also the most difficult particles for an air filter to remove. Filters, which are specifically designed to remove these most difficult particles, are called HEPA filters, and these are the best ones to buy.
• Filter vacuum cleaners – the small size of the most troublesome particles means that they pass straight through the coarse filter and dust bag of a normal cleaner and are blown around the room (thus many dust allergic people are worse after vacuuming). Simple measures include getting someone else to vacuum, opening windows wide during vacuuming, and not doing it so often – damp dust instead (but not with a cloth that is too wet, or humidity will rise). Ideally an old vacuum cleaner should be replaced with one that is designed to effectively trap even the sub-micron particles which cause the problems. There are a range of options, from expensive but very effective purpose built machines, through to standard models fitted with special microfilters, to filter material which can be added to your existing vacuum cleaner if you can’t afford a new one. Whichever type you choose, you should be sure that the filter vacuum effectively removes particles down to half-a-micron or so. A more powerful machine will suck up more dust and therefore steadily reduce the ‘reservoir’ of housedust mite left in furnishings.

Pollens and Moulds
Grass pollen is commonly considered; tree and weed pollens are often ignored but as each has it’s own season ranging from January (Hazel) to October (Dandelion). Air filters are effective indoors (pollens are relatively large particles, although fragments are obviously much smaller). Filter vacuum cleaners will trap pollens.

Mould spores are usually ignored but are potent allergens – very few allergic patients are not mould sensitive. Different moulds spore at different seasons, so mould sensitivity (as with pollens) can lead to year long symptoms, usually worse in spring and particularly autumn, in damp weather, when raining or snowing, and in gardens, around compost heaps, and when cutting grass. Measures to reduce humidity, increase ventilation, and good air filters will help tackle mould sensitivity, as may avoiding ‘mouldy’ foods such as blue cheeses, mushrooms and yeasts.

If you have a damp house, particularly where mould is visible on walls and windowsills, it is important to determine the cause and tackle it (either structural faults, or condensation due to inadequate heating or poor ventilation)

Source: http://www.allergyuk.org

To be continued....................