Posts Tagged ‘common allergens’

Many countries have special schools for children with severe asthma and other allergies. Italian children are sent to one in the Italian Alps, where there is no trace of pollen, house-dust mite, or animal allergens. After nine months these children are a great deal healthier and more active - all their lung function tests are vastly improved. Blood tests show that they are actually less allergic to common allergens than before.
You may not be able to do quite this well at home, but all allergens and irritants can be avoided to some extent. Even if you can’t eliminate them completely, you can certainly reduce your exposure.
Before you start, it is important to be clear about exactly what affects you, otherwise you will be wasting a lot of effort. For example, people who are allergic to dust mite often think that a dusty house will necessarily be worse for them than an apparently clean house, but this is not so (see p. 115). Or they may say ‘Oh, I got asthma on holiday, because the roads were so dusty and I’m allergic to dust,’ forgetting that only house dust contains dust mites. The road dust may have acted as an irritant, and helped to spark the asthma attacks, or it may have contained pollen or mould spores - but it does not contain dust mites or their allergens. Blaming the wrong thing for the asthma attack means that the real culprit is not identified.
If you are not absolutely sure what causes your allergies, skin-prick tests (see p. 91) can identify the allergen. These are especially recommended if your reactions to the presumed allergen are inconsistent, or you don’t respond to the anti-allergen programmes described here. For example, a few people who react to house dust are not allergic to dust mites, but to something else in the dust such as wool fibres or mould spores, or particles from cockroaches, house
flies, carpet beetles or a long-departed cat. Even pollen that has accumulated in house dust can provoke allergic reactions - if you are not an over-keen duster, it can still be there long after the pollen season.
If you have hayfever, knowing which pollens cause your symptoms (and learning to recognise the plants concerned) is useful. You will probably need skin-prick tests to be sure. ‘Hayfever’ can even be a seasonal mould allergy in some people (see p. 27).
Tackling allergens is now big business. There are a lot of people out there competing for your money and false claims are common, especially for anti-mite products. Only a few manufacturers are deliberately misleading, and most false claims probably stem from ignorance or wishful thinking, but be very sure you know the facts about your allergen before you buy.
Air cleaners are a good example. A really good quality air cleaner (which uses a HEPA filter - a High Efficiency Particulate Air filter) is an expensive purchase and, as the advertising tells you, it takes out very small particles with staggering efficiency. But this is entirely irrelevant if the source of those particles is no distance at all from your nose - your mite-infested pillow, for example, or the cat on your lap.
Something else that advertisements for air cleaners rarely mention is that unless you reduce allergen production - tackling mould growth in the house, for example, or keeping the dog outside - the filter can’t help much. In short, air cleaners do have their uses for some allergens, but they can’t work miracles.
The products mentioned here, if not available in your locality, can be bought mail-order from specialist suppliers of anti-allergy products (see p. 255). Note that some offer both very good products and distinctly doubtful products, so judge each item on its individual merits. Ask to see scientific evidence that it works.
Don’t be taken in by vague statements such as anti-allergenic’ - get the facts. This label is often used on pillows with synthetic filling, for example, and people assume that it refers to dust-mite allergy, whereas it simply means that the pillow does not contain feathers. But unless you are allergic to feathers, there is no reason to avoid feather pillows. (In fact, if not covered with mite-proof covers, synthetic pillows collect more dust-mites than feather pillows, because the fabric used for the cover is less tightly woven and the mites and skin particles get in more easily.)
Bad advice is also a hazard. Some of it just wastes your time and effort, but some could actually increase your exposure to the allergen. Advice to vacuum floors daily, or to vacuum beds, is commonplace but this achieves little and it means breathing much more allergen unless you have the right kind of vacuum cleaner. One health magazine even advised its readers with dust-mite allergy to ‘air mattresses by regularly turning them’. This will not affect mite numbers at all, but it will shoot massive amounts of mite allergen out of the mattress and into the nose and lungs.
Ridding your house of allergens and irritants is, in itself, a hazardous procedure because more of the offending substances will be released into the air during the work. If you take up carpets or remove mattresses, dust-mite allergens and mould spores will be churned up in their millions. Just bundling up a duvet will produce invisible clouds of dust mite allergen - and cat allergen, if your pet once slept on the bed.
Ideally, the allergic individual should not do the work, nor be in the house until it is 100% complete and the house has been very thoroughly aired. This is particularly important for those with chronic sinusitis and mould growth in the house, because of the risk of fungal infections in the sinuses (see p. 32).
If you are an allergy sufferer and have absolutely no choice but to do the work yourself, or to be present, then you should get a good quality dust mask and wear it throughout - only take it off when you go outdoors. Those with atopic eczema and sensitivity to airborne allergens should cover their skin carefully -with clothing, not barrier cream.
An ordinary hardware-shop dust mask is not adequate for most allergens - it only takes out really big particles and lets through all the common airborne allergens except pollen. You need a more serious sort of mask, designed for workplace use and conforming to official standards. Before buying one, ask what is the smallest size of particle that it filters out (at 90% efficiency, or better). Compare this with the particle size of your allergen (given in the articles that follow).
You must be able to breathe well through the mask when physically active, and it must fit tightly against your face, forming a seal at all edges. Beards and moustaches tend to prevent this - as does stubble.
Masks that combine an activated carbon filter with a dust filter will take out gases and chemical vapours as well as particles. Cycle shops now sell such masks -or try an industrial supplier. Such a mask can be useful if you are affected by traffic exhaust or industrial pollution as well as an allergen, for example, or if you are exposed temporarily to wet paint or other fumes at home. Activated carbon masks should also filter out the irritant substances from oil-seed rape plants.
Some people who try the anti-allergen programmes feel much better quite fast. But generally these are long-term strategies - you may not reap any benefits for a few weeks, and the improvement may be small at first. Sometimes it takes several months for the full effects to be felt, so be persistent.

Atopic eczema
A Greek word meaning ‘to boil over’ or ‘to erupt’ is the source of the medical term ‘eczema’. It refers, of course, to the way in which the skin erupts into a rash, but it could equally well describe the eruption of controversy around this disease. No other allergic disease is quite such a cauldron of dissent - indeed, even the question of whether it is an allergic disease remains unresolved. These controversies directly affect the treatment of atopic eczema, so it is useful to understand them if you or your child have eczema.
The disagreement begins with the question of what causes atopic eczema.
Let’s start with the one point that everyone agrees on: dry skin plays a fundamental role. Those with atopic eczema have dry skin, not just in the eczematous areas, but in other parts as well, sometimes all over the body. The skin cells are less efficient than normal skin cells at retaining water.
Everyone would also agree that there is inflammation of the skin – a reaction that is produced by the immune system. But when it comes to the question of what starts off the inflammation there are huge differences of opinion among specialists treating atopic eczema – these specialists include dermatologists, allergists and paediatricians.
Since people with atopic eczema are atopic (allergy-prone), and most have
huge amounts of the allergy antibody, IgE, going round in their blood, it might
seem plausible that an allergic reaction to some external item kicks off the
inflammation. And when skin-prick tests (see p. 91) to common allergens such
as house-dust mite are tried, there are usually a large number of positive results.
But many of these turn out to be false positives – when tested more directly,
the allergen concerned does not actually play a part in causing the skin symptoms.
This has led some specialists working with eczema, mainly dermatologists, to
What the words mean
Eczema is not a disease in itself. The word refers to a certain type of reddish rash — a rash which can be caused in a variety of ways. The type of eczema that affects people of an allergic disposition (atopics), is called either atopic eczema or atopic dermatitis.
The word dermatitis just means inflammation of the skin. Most doctors consider it to be synonymous with eczema, but some give it a slightly broader meaning.
believe that allergic reactions play little part in either initiating or perpetuating atopic eczema. In their view, the basic cause of atopic eczema is dry skin and a generally overwrought immune system, not specific allergic reactions.
To some of these doctors, positive skin-prick tests are all false positives in atopic eczema – that is, irrelevant to the disease process. A positive skin-test result, in their opinion, simply indicates that the skin of atopic eczema sufferers is in a highly sensitive state, not that the allergen concerned plays any causative role.
Allergists tend to take a different view of this, as you might expect. And recent research shows that they are correct – allergens often do play a significant part in provoking atopic eczema.
Research using direct challenge tests (see p. 90) has identified some of the things that could provoke such sensitivity reactions:
• house-dust mites, pollen or moulds
• cats, dogs, rabbits and other furry pets
• cow’s milk or other food – a prime suspect in babies and young children (see p. 68). The response to food is usually delayed, occurring some hours after the item is consumed.
With mite, pollen and pet allergens, the eczema symptoms can be provoked either by allergens falling on the skin, or by direct contact (e.g. mite allergens in the bed, skin contact with pets, or lying on grass for those with grass-pollen allergy).
The rash tends to occur on skin not covered by clothes, as you would expect. But it can sometimes occur only on particular exposed areas – usually the most sensitive areas of skin. For example, there are people who react to house-dust mite but have eczema on the eyelids only.
Additionally, experiments show that even when an airborne allergen is only inhaled it can sometimes provoke eczema symptoms. The allergen probably reaches the skin in the bloodstream. (Alternatively, it might provoke an immune reaction in the airways which generates chemical messages of the kind that promote inflammation – these then reach the skin in the blood.) This means that the skin reaction could occur anywhere on the body, not just on exposed skin.
In the case of food, the molecules of food that cause the trouble are probably being absorbed from the stomach without being completely broken down. They then reach the skin via the blood to provoke a reaction there. (Or, again, it could be an inflammatory messenger chemical travelling from the gut to the skin in the blood.)
When food gets directly onto the skin – which it frequently does with small children, of course – it can provoke a reaction that way too. This may be a slow eczema-causing reaction, or a much faster reaction known as contact urticaria (see pp. 50-51). Reacting to food with contact urticaria is quite common in children with atopic eczema – but the same food doesn’t necessarily provoke atopic eczema when it is eaten. (However, eating these foods can sometimes trigger anaphylaxis – see pp. 58-9. They should therefore be treated with great caution.)
At the same time as all this research – which shows for sure that allergens play a part in atopic eczema – others have been asking what actually happens when skin reacts to an allergen. Their studies have turned the accepted understanding of allergies upside-down. They show that when something like egg or pollen provokes atopic eczema, what is occurring isn’t necessarily an allergic reaction of the usual sort, with IgE and mast cells (see
box on p.12). Instead, other immune cells are causing the trouble. Sometimes IgE is involved, but without mast cells. Sometimes neither is involved. These revolutionary discoveries are described in more detail on pp. 18-19. One interesting realisation from this research is that in different eczema sufferers, different immune reactions may be producing the rash – even if they are reacting to the same allergen! This helps to explain why the results of skin tests are so inconsistent and puzzling.
The wandering rash
For a baby with atopic eczema, the face, and especially the cheeks, are commonly affected, but there may be a rash all over the legs, the backs of the arms, and the back. As the months go by, the rash settles on the lower legs, and spreads to the fold of the elbow, and then the fold at the back of the knees — by about three years of age, this flexure eczema is the main problem for most children.
In adults, eczema is often found in quite restricted areas, such as the hands, scalp, lips, eyelids or chest. It may be located around the nipples — a sensitive spot where rubbing by clothing is enough to initiate a rash.
Atopic eczema is always in a process of change, and different parts of the body may display different stages of the rash:
• The rash is red and usually dry at first, and there may be not a great deal to see. In this early stage the visible signs may be minimal, while the itchiness can be colossal. Sometimes there is oozing of clear fluid.
• Occasionally the first phase is more marked, with dense patches of small red bumps or tiny blisters. On the hands, these may merge to form larger blisters.
• Infections tend to change the appearance of the rash (see p. 44).
• With time the skin becomes thicker, paler and scaly. It may form leathery patches (called lichenification), especially if there is habitual scratching or rubbing. This is chronic eczema.
• When the eczema clears, there may be an area of skin that is lighter in colour, or darker, than the surrounding skin.
The next step
Whatever causes atopic eczema, it provokes the most horrendous itching, as every eczema sufferer knows. The itch cries out to be scratched, and scratching is the major cause of the visible rash. If left untouched, the skin does not erupt into eczema, although it may well turn red, and there are still distinct changes in the skin that can be seen with a microscope.
Once eczema has erupted, the skin is no longer an intact protective layer that neatly separates ‘in-here’ from ‘out-there’. The skin becomes more permeable and loses its own natural moisture far more readily, so the dryness gets worse. At the same time allergens and irritants penetrate far more easily, causing yet more inflammation.
Something else compounds the damage: once atopic eczema is established, the immune system starts making IgE antibodies to the body’s own proteins, especially those found in skin cells. This helps explain why atopic eczema can become so severe and so entrenched.
Infections — another vicious circle
When eczema erupts and the skin barrier is breached, infections often become a problem. A regular source of trouble is the bacterium Staphylococcus aureus, a cause of the infection impetigo. This microbe invades eczematous skin far more readily than healthy skin, causing a prolific ooze with golden-yellow crusting.
Staphylococcus aureus produces a toxin known as a ’super-antigen’ which revs up the immune system to even more furious effort. This effort does not, unfortunately, oust the bacteria, but it does make the skin inflammation even worse. To add to their woes, many who are afflicted with atopic eczema start making IgE antibodies against Staphylococcus aureus toxins.
Infection with fungi (yeasts and moulds) is also a problem in atopic eczema (see p. 49), and there may be sensitivity reactions to these fungi.
The herpes virus, responsible for causing cold sores, can also invade eczematous skin, though this is much rarer. It worsens the eczema and produces fever and general weakness. There may also be flocks of small red bumps, each with a tiny dimple or blister at the centre. Any symptoms of this kind indicate that the patient needs urgent treatment.
Irritants and stress
People with atopic eczema are far more susceptible to everyday irritants such as wool and rough synthetic fabrics, soap, and traces of detergent left behind in clothes. Chlorinated water, either in swimming pools or from the tap, can also aggravate the skin, and even ‘hard’ water (found in areas with chalk or limestone bedrock) may be a factor.
Some air pollutants may play a part in atopic eczema. Researchers in Germany have found that children living close to busy trunk roads, or in homes with a gas cooker and no extraction hood (see pp. 128-9), were more likely to develop eczema. Formaldehyde fumes, often found in modern houses (see p. 129), are sometimes a factor when eczema affects the face and hands.