Posts Tagged ‘simple answer’

Allergy: Selecting the Right Food

An avoidance diet is for people who already know what food or foods affect them, and simply need to

avoid those foods. A diagnostic diet is for those whose symptoms suggest that they might be suffering

from food sensitivity of some kind, and who cannot be diagnosed by indirect methods such as skin tests,

because true food allergy is not involved. A diagnostic diet is intended primarily to show whether or

not food is causing the symptoms.
The diagnostic diets themselves fall into two basic categories. Firstly, there are diets that, by a

process of elimination, identify a particular food (or foods) as a cause of symptoms. Called

elimination diets, these are used to diagnose idiopathic food intolerance (see p. 74) and certain other

kinds of sensitivity reactions to particular foods. An elimination diet is purely diagnostic - simply a

means to establish which foods are at fault. To this end, all commonly eaten foods are avoided at the

outset, and each food is then tested individually. Once an elimination diet is complete, the

information gathered is used to establish a suitable avoidance diet. For example, if milk, wheat and

oranges caused symptoms during the testing phase of the elimination diet, those foods are all avoided

in future.
Secondly, there are specific diagnostic diets, which are a great deal simpler to carry out than

elimination diets. A specific diagnostic diet aims to reduce the intake of a particular substance that

is found in certain foods. The substances concerned -histamine or nickel, for example - are known to

cause particular symptoms in susceptible people.
A specific diagnostic diet simply cuts out all the foods that contain large amounts of the substance
under suspicion. If this diet alleviates the symptoms, and does so consistently, it is plausible that

the substance concerned is indeed the culprit. However, the diet should be stopped and then started

again, preferably several times, to check the response. Once the sensitivity is confirmed in this way,

the avoidance diet which follows is basically the same as the diet used for diagnosis.
Note that there is no agreed terminology for these different kinds of diet, and the definitions given

above will not necessarily be followed in other publications. You may even come across ‘elimination

diet’ being used to mean ‘avoidance diet’, which is particularly confusing. If you are consulting other

sources of information, check the context carefully to see what meaning is intended.
There is one odd man out in this chapter - the diet to protect against asthma, described on pp. 206-7.

It is neither an avoidance diet nor a diagnostic diet, but a health-promoting diet of the kind commonly

advocated to combat other widespread conditions, such as cancer and heart disease. In fact, it has a

remarkable number of similarities to diets that reduce the risk of these other diseases.
The anti-asthma diet is immensely healthy, whereas many avoidance diets carry a risk of malnourishment.

An allergic individual following any kind of restrictive diet - especially a child - should be

medically assessed for the possible risks. That is why it is important to talk to your doctor before

starting any dietary treatment or investigation. A referral to a dietician or nutritionist may be

necessary, and your doctor can arrange this.
When malnutrition does occur as a result of self-treatment, there are often very complex factors at

work. One potential hazard with dietary treatment is that psychological problems can easily become
entwined with obsessions about food. Eating can be a potent form of self-expression, or a way of

exerting control over oneself and others. Many doctors have seen patients who are mistakenly convinced

that food sensitivity is at the root of their health problems, or those of their children. In some

cases, no amount of objective evidence to the contrary will deflect people from such beliefs.
A few people with mistaken beliefs of this kind impose very restrictive diets on themselves - or

sometimes on the whole family. The food rules that they establish may be a way of limiting contact with

the outside world, avoiding other problems and issues by making diet the central focus, or simply

making demands on other people’s time and attention.
The current fad for identifying ‘food allergy’ using very dubious diagnostic tests (see p. 93) will

probably send many more psychologically vulnerable people down this route.
Another unhelpful trend in the dietary field is the wholesale (and usually ineffective) use of

vitamins, minerals and other supplements for a great variety of diseases, including allergy and other

forms of sensitivity. It is important to realise that none of the sensitivity diseases described in

this book has nutritional deficiency as its primary cause, so supplements are not a major part of

treatment in most cases. For the majority of people with some kind of sensitivity disease, a supplement

will make only a small difference, if any. However, it is true that, with some sensitivity problems,

certain supplements may be helpful to certain individuals. The use of Vitamin C in asthma (see p. 207)

is one example of this, and there are some other instances mentioned in Chapter 2.
Generally speaking, it is better to get the vitamins, minerals and other nutrients you need (such as
antioxidants) from food, not from tablets. Studies of adult-onset asthma have shown that only natural

Vitamin E protects against the disease: supplements have no effect.
Many vitamins and minerals, along with various plant and animal extracts, are now referred to as

nutriceuticals - in other words, substances that are classed as nutritional supplements for legal

purposes, but are being marketed as if they were medicinal drugs (pharmaceuticals). Many doctors are

concerned about this, if only because of the duplicity involved. These substances can be sold freely to

the public only because they are, in theory, nutritional supplements, yet they are actively promoted to

the public as if they were drugs.
The marketing is usually indirect, to avoid falling foul of the law, but very effective nonetheless.

Advertisements for the product avoid making any medicinal claims, since these would be unlawful, and

just speak vaguely of ‘health-giving properties’. The specific medicinal claims are made in magazine

articles (which often appear right beside the advertisement), penned by journalists who have been

supplied with a great many ‘facts’ - actually unsubstantiated claims -by the manufacturer of the

supplement. These claims are reproduced uncritically, so the journalists are simply acting as

mouthpieces for the manufacturer. There is no law preventing this.
This is a ruse that circumvents important laws intended to protect consumers from misleading

advertising. Few of these products are likely to be damaging - although there are concerns about some,

especially beta-carotene supplements (see p. 207). What matters here are the large amounts of money

being made from products that frequently have few benefits for those who take them.

What exactly is in ready-made food? People with food sensitivity, especially those with severe food

allergy or coeliac disease, need a simple answer to this question, but frequently they don’t get one.

Research among food-allergy sufferers has found that, in the course of a year, half of them

inadvertently eat the food they are trying to avoid, owing to a lack of information about ingredients.

Restaurants and canteens are responsible for many of these accidents, and most of the fatalities (see

p. 111), but packaged food also plays a part.
Unfortunately, many food ingredients that are potentially allergenic, such as milk and eggs, appear in

packaged food without this being stated on the label in everyday language. The information is usually

there somewhere, however – you just need to know what words to look for.
Decoding food labels
The problems with food labels fall into two general categories:
•    some of the ingredients are described using technical terms. These are usually specific

constituents of the original foodstuff e.g. lactalbumin, one of the proteins found in milk.
•    some manufactured ingredients can be made from different starting materials. So an item such as

‘edible starch’ could be made from either wheat or maize (corn), while ‘hydrolysed protein’ could be

made from soya, maize or yeast, sometimes with wheat added.
One day, no doubt, manufacturers will realise what a burden this type of obscure labelling imposes on

their allergic customers and will start using plain language. In the meantime, food-allergy sufferers

just have to learn all the terms that may be used for their culprit food or foods.
Labels used in health-food shops and delicatessens are another matter altogether. Here the problem is

with exotic-sounding items, such as kamut, which is actually an allergenic food (wheat).
Maize (Corn)
Items always made from maize: cornflour, cornmeal, cornstarch, dextrose, polenta
Items sometimes made from maize: baking powder, cereal starch, edible starch, food starch, glucose

syrup, hydrolysed protein, hydrolysed vegetable protein, malt, malt flavouring, modified starch,

modified food starch, starch, textured vegetable protein, vegetable gum, vegetable protein, vegetable

starch
Note that the gum on envelopes and stamps is sometimes made from maize, and that many medicines contain

cornstarch.
Eggs
Items always made from eggs: ovalbumin
Items sometimes made from eggs: lecithin (In fact this is rare in foods – lecithin is usually derived

from soya. Only in pharmaceuticals is lecithin likely to be derived from egg.)
Terms used for egg on cosmetics and toiletries: Ovum
Fish
Be very cautious when travelling. The use of fish meal as an ingredient of spicy sauces is common in

Southeast Asia, and in some parts of Africa. The strength of the spices may make the flavour of the

fish undetectable.
Milk
Items always made from milk: casein, casemate, lactalbumin, whey
Terms used for milk on cosmetics and toiletries: Lac
If you see the term ‘dairy-free’ on standard packaged foods, you can safely assume that the contents

are free from goat’s and sheep’s milk, as well as cow’s milk. But be more wary with homemade or locally

produced foods labelled ‘dairy-free’ - some
people think that ‘dairy’ refers only to cow’s milk.
Parev or pareve is a term used for kosher (Jewish) food that contains neither milk nor meat. However,

there can be contamination with traces of milk.
Lactose is a sugar produced from milk, and while it is not allergenic itself, it may contain a trace of

allergenic milk proteins. The amounts involved are tiny, and will only affect the most sensitive

individuals.
The label ‘non-milk fat’ sometimes misleads people if they just glance quickly at labels. The fact that

a product contains non-milk fat does not, of course, mean that it is entirely milk-free -remember to

look for all the synonyms of milk (see above).
Nuts
Items always made from nuts: frangipane, marzipan, praline
Standard packaged food will almost always include the nuts by name, but if you are buying other food

(e.g. from a stall selling home-made food) watch out for the above names.
Be very cautious about unrefined nut oils (see p. 110). Almond essence may be produced chemically, in

which case it is safe, but some is made from real almonds and could be allergenic.
Terms used for nuts on cosmetics and toiletries: Prunus, Juglans, Bertholletia, Corylus
Peanuts
Items always made from peanuts: arachis oil, groundnut oil satay sauce
Unrefined peanut oil should be avoided. This is not much used, and unlikely to be encountered except in

Indian and Oriental cooking. Most groundnut oil sold in Britain and Europe, or used in packaged foods,

is refined and considered safe (see p. 110).
Alternative names: arachide, beer nuts, cacahuete, earth nuts, goobernuts, groundnuts, monkey nuts
You are only likely to encounter these names on imported food, or when travelling. Always be very

careful with Indian or Southeast Asian food, where the use of peanuts is very common and often not at

all obvious. Avoid chocolate from Poland, which often contains peanuts that are not declared on the

label.
Items sometimes made from peanuts: hydrolysed vegetable protein. (The usual source is soya or wheat,

but some is derived from peanuts.)
Terms used for peanut on cosmetics and toiletries: Arachis hypogea, Arachis oil
Sesame
Items always made from sesame or containing some sesame: gomashio, halva, hummus (houmus), tahini, the

drink Aqua Libra
Alternative names: ajonjoli, berme, gingelly, teel, til, simsim
Check carefully for sesame in any food from a health-food shop or a stall selling home-made food, and

in foods from the Middle East, or Chinese packaged food (e.g. stir-fry oils). Sesame oil is always

unrefined and therefore allergenic (see p. 110). Watch out for contamination by traces of sesame in

bakeries and delicatessens where goods are sold unwrapped.
Term used for sesame on cosmetics and toiletries: Sesamum indicum
Shellfish
Items sometimes containing shellfish: curry paste, fish sauce and other sauces/pastes used in Southeast

Asian cooking
Standard packaged food should mention shellfish specifically, but you may need to read the label

carefully. Be cautious about bottles of imported sauce, and home-made or takeaway food.
Soya
Items always or usually made from soya: miso, soy sauce, textured vegetable protein, tofu, vegetable

protein
Items sometimes made from soya: hydrolysed protein, hydrolysed vegetable protein, lecithin, vegetable

gum, vegetable starch Changes in ingredients
Unfortunately, the ingredients of a product can change without any obvious warning on the label, or any

change in the packaging. You should always check the label in detail, every time - even on foods that

you have eaten before without any trouble.
Wheat
Items always made from wheat: bran, flour, graham flour, hard flour, strong flour, wholemeal flour

(there are non-wheat brans and flours, of course, but the words ‘bran’ or ‘flour’, without any

qualification, usually mean wheat)
Regional names for particular types of wheat: bulgur or bulgar wheat, Chilton, couscous, dinkel, durum,

einkorn, farro, fu, kamut, semolina, spelt, triticum, triticale (a hybrid of wheat and rye)
Items sometimes made from wheat: baking powder, cereal binder, cereal filler, cereal protein, cereal

starch, edible starch, food starch, hydrolysed protein, hydrolysed vegetable protein, modified food

starch, modified starch, starch, textured vegetable protein, vegetable protein, vegetable starch.
Assume that bread, crispbread, pastry, pasta and noodles are made from wheat, unless definitely

labelled otherwise (and read the label in detail too, because a little wheat is often added to items

such as rye bread and rye crackers).
Note that buckwheat is not wheat at all - it is not even a cereal. Nor does it commonly affect

coeliacs, as is sometimes claimed, though a few coeliacs may develop an intolerance reaction to it,

through eating it very regularly.
For more information on avoiding gluten, see p. 177.
Yeast
Items usually made from yeast: leavening
Items sometimes made from yeast: hydrolysed protein, hydrolysed vegetable protein
Labelling loopholes
Manufacturers do not have to include on the label:
•    Any ingredients used in an earlier manufacturing process e.g. yeast used to make bread for

breadcrumbs, wheat flour added to spices or mustard powder during the grinding process, or bread used

to innoculate blue cheeses with mould -this can leave minute traces of gluten in the cheese.
•    Residues left by substances used during processing, such as wheat flour used to dust processing

lines or prevent dried fruits from sticking together. Manufacturers do not need to declare these

residues on the label because the substance serves no function in the final product and is present in

amounts that are considered insignificant. The vast majority of those with coeliac disease or food

allergy will tolerate such microscopic traces, but the most sensitive individuals may not. Some

coeliacs are even affected by food additives manufactured from cereals (see p. 177).
•    The individual constituents of a composite ingredient (such as salami on a pizza), if that

composite ingredient makes up less than 25% of the finished product. This is called the 25% rule. As

from November 2005, this is all set to change, thanks to the European Parliament. The contents of a

composite ingredient like salami will be listed in full. A few composite ingredients with officially

defined contents (such as jam, or chocolate) can be listed just as ‘jam’ or ‘chocolate’ if they make up

less than 2% of the product. Likewise herb mix or spice mix, if less than 2%. But there are certain

items that must always be listed if they are anywhere in the product, and however small the amount.

They are: milk, eggs, tree nuts, peanuts, sesame, mustard, celery/celeriac, fish, crustacean shellfish

(shrimps, prawns, crab etc), soya, wheat and all other cereals that contain gluten. Sulphur dioxide and

sulphites must be listed if more than 1 Oppm. This list will be reviewed from time to time.
`May contain’ labels
Labels reading ‘May contain nut traces’ are springing up like weeds on packaged food. Similar labels

relating to sesame, milk and eggs are also starting to appear.
Allergy sufferers, suddenly unable to eat foods that they formerly enjoyed, feel very frustrated about

this development. Many suspect that these labels are often just a defensive tactic - warning off

consumers with food sensitivity when the chance of the food containing the allergen is actually very

small. The danger is that some allergy sufferers may stop taking the labels seriously. Teenagers, in

particular, are increasingly dismissive of ‘May contain’ labels, and this is a huge worry for parents.
Could the need for ‘May contain’ labels be eliminated altogether with more careful factory procedures?

The problem here is that, with nuts, perfect cleaning of production machinery is extremely difficult.

Most machines have nooks and crannies in which a nut from one production process can become lodged,

only to free itself later during the making of a non-nut product. It is quite possible that someone

could encounter a whole nut, or substantial pieces of nut, in a non-nut product. That is why no one

with nut allergy, even if it is relatively mild, should disregard ‘May contain nut traces’ labels.
Some makers of confectionery and biscuits have now set up dedicated nut-free production lines, with

stringent precautions to avoid any possibility of contamination. This allows them to market products

that are guaranteed nut-free. If you cannot purchase these locally, you may be able to order them by

mail or over the Internet (see p. 255).
Note that packaged foods that have been produced on nut-free production lines in the past can be

switched to different production lines, that necessitate a ‘May contain nut traces’ label.
In some cases, a product is manufactured in two separate places, one of which is nut-free, while the

other is not. Consequently, the same product may sometimes be sold with a ‘May contain’ label and

sometimes without. Don’t disregard these labels, however illogical they might seem.
Packaging errors
As most people with food allergy are now aware, ready-made foods sometimes go out in the wrong

packaging. Alarming cases that have occurred in recent years include hazelnut yoghurts labelled Toffee

Yoghurt, and Vegetable Bake (containing nuts) sold in packets intended for Vegetable Lasagne (no nuts).
Manufacturers are increasingly aware of the hazards and when mistakes are discovered, allergy

information websites and organisations such as the Anaphylaxis Campaign are quickly informed, so that

they can alert allergy sufferers.
Belonging to such an organisation (see p. 255), and/or checking websites regularly, is definitely

recommended for anyone with food allergy. However, you should bear in mind that no information service

can protect you completely from this hazard. The odds against it are high, but one day you might just

be the unlucky person who first discovers a packaging error by suffering an allergic reaction. To

protect yourself as far as possible:
When is a nut not a nut?
Those with nut allergies often worry about eating nutmeg and coconut. In fact, allergic reactions to

these are rare. People with nut allergy are no more likely to react to nutmeg or coconut than anyone

else.
Tiger nuts or chufa nuts are not nuts at all, but the roots of a sedge plant – they are most unlikely

to cross-react with true nuts.
Peanuts, botanically speaking, are not true nuts at all. They are legumes (pulses). There can be

cross-reactions with soya and/or lupin (proceed very carefully with this novel food ingredient) but

reactions with other pulses are rare. Cross-reactions with tree nuts such as almonds and Brazils are

quite common however (see p. 15). Many people with peanut allergy can in fact eat tree nuts, but they

should be aware that a cross-reaction could develop at some stage.
Because cross-reactions between tree nuts are so common, doctors tend to speak simply of ‘nut allergy’.

However, it is possible to be allergic to one type of tree nut, without being allergic to others.
•    always check that the food in the packet looks like the photograph on the packet
•    double-check, when you serve the food, by noting the conspicuous ingredients of the meal

(carrots, for example), and ensuring that they are indeed on the list of ingredients – any discrepancy

should make you suspicious
•    note the smell and appearance of any ready-made food, before you taste it. Do this even for

very simple things such as flavoured yoghurts
•    only have a very tiny mouthful at first, and if you have any tingling of the lips or other

symptoms, however mild, stop eating immediately (this is helpful for true food allergy only, not for

coeliac disease)
•    be especially cautious about vegetarian food if you are allergic to nuts or soya.
Latex in food
Those with latex allergy may react to very small traces of it in food. This sometimes occurs with

packaged food or restaurant food that has been prepared by workers wearing latex gloves. On one

occasion a highly allergic individual reacted to a water glass that had been handled by someone wearing

latex gloves. The amounts of latex involved are minuscule, and only affect those with severe latex

allergy. However, there is a strong case for workers handling food to wear non-latex gloves, especially

with the rise in cases of latex allergy.
There are also reports of people with latex allergy reacting (usually very mildly) to cold-seal

adhesives in food
wrappers, such as those used for ice cream. The reaction only occurs if the wrapper actually touches

the lips or mouth.

`I can’t think of any of our friends where there isn’t at least one member of the family with asthma, and often it’s both children,’ says Dee Gill, a university lecturer from Melbourne, and herself asthmatic. Australia is one of the countries worst affected by the allergy epidemic. ‘If you go to a primary school sports day, you’ll see the teachers going along the line of kids, saying, “Have you taken your asthma medication?” It’s so much a part of everyday life now.’
The word ‘epidemic’ is now being freely used, even by the most conservative of medical scientists. All the classical allergic diseases seem to be on the increase, including:
• atopic eczema – in the United States, up from 3% of children in the 1960s to 10% in the 1990s; in Britain, more than 16% of 12- to 14-year-olds are now affected
• hayfever – extremely rare in the 1930s (26), affecting 3% of children in 1964, and now seen in 18% of 12- to 14-year-olds in many parts of the world
• asthma – the figures for children in one Scottish city are: 4% in 1964, 10% in 1989, nearly 20% in 1994
• peanut allergy has clearly been on the increase since the 1960s; a very alarming UK study shows that rates of allergy to peanuts have doubled in less than a decade (between children born in 1989 and those born in 1996).
To the question ‘why?’ there is no simple answer – the causes are many and various. But one thing is abundantly clear: this is a disease of modern, Westernised society. Travel to rural Africa or
Are other immune diseases increasing?
These two pages deal solely with the classical allergic diseases . Many doctors have the impression that eosinophilic disorders are also becoming more common, and some think that there are more cases of adult-onset coeliac disease than previously.
Asia, among people living a simple subsistence lifestyle, and you will find little or no sign of allergic diseases. There are no words in their languages for asthma or hayfever, because these are virtually unknown.
As soon as these people become more affluent, and change their lifestyle, allergic diseases appear, and the number of cases steadily rises over the years. Sometimes this coincides with a move to the towns, but it can also occur when people stay right where they are – as in Taiwan, where allergies rose dramatically with increasing affluence and a more Westernised way of life.
In the case of asthma, everyone is keen to blame air pollution, particularly traffic pollution. But a look at the research shows the link to be largely a myth. Certainly, polluted air can trigger off attacks in someone who already has asthma – but the effect is not huge, and this is not the same as causing asthma to develop in the first place. And while growing up in polluted air can increase the chances of children developing asthma, it makes only a small difference, one that simply cannot account for the massive asthma epidemic. The hollowness of the pollution argument is spectacularly evident when you consider rural New Zealand, where asthma rates are among the highest in the world, yet there are no factories, and sheep heavily outnumber motor cars.
Allergy to house-dust mites has also received a lot of publicity, and it does play an important part. Our warm, draught-free and thickly carpeted homes allow these tiny creatures to breed with abandon and many people with perennial rhinitis, asthma or atopic eczema have an allergy to dust mites. Recent research shows that dust mites play a far larger role than anyone previously suspected: the dust-mite allergen actually provokes immune cells, and once an allergy to dust mite has begun, other allergies become more likely.
But blaming house-dust mite as the supreme cause of the allergy/asthma epidemic (as some do) is as mistaken as blaming pollution. The proof in this case comes from the highlands of New Mexico where dust mites cannot survive because the air is much too dry. Allergies, including asthma, are just as common as elsewhere in the Western world.
Spoiling the immune system
Thanks to discoveries made during the past decade, we are now beginning to understand what has made the younger generations – those born since the early 1960s – so much more susceptible to allergies. The new data reveal that the way you bring up a child’s immune system matters as much as the way you bring up the child itself. You can ’spoil’ an immune system all too easily, by protecting it from life’s natural challenges and obstacles.
As a small child, I ate a spoonful of soil. My mother was horrified (she was still telling the story twenty years later) but research now shows that she should not have been. Exposure to certain bacteria in the soil, known as mycobacteria, is probably just the kind of education that a young immune system needs. These bacteria cause no 111-health, no symptoms at all, but they are thought to have an effect on the immune system, pushing it away from allergic reactions.
Children playing outdoors have probably always eaten soil, either intentionally or by accident – licking a grubby finger. Country people used to say, philosophically, ‘You eat a bushel of dirt before you die’, and they were probably right. Indeed, you may well need to eat a bit of dirt before you can live happily in an allergen-packed world. Now researchers are trying to make a vaccine using soil bacteria, to simulate this effect.
A study from the University of Bristol shows that children who wash their hands more than five times and have two baths a day are almost twice as likely to get asthma as children who wash their hands less than three times a day and have a bath every other day. The grubbier children are probably being protected from asthma by acquiring minor infections, with few or no symptoms. These infections could include both soil bacteria and germs that are spread from one child to another.
Other research reveals that children with older brothers and sisters are less likely to suffer from certain allergic diseases than only children or firstborn children. This may be due, in part at least, to the spread of infectious diseases, because mixing with lots of
other children in a nursery produces more infections but also gives protection against allergy. Studies from the former East Germany, where sending children to day nurseries at an early age was once the norm, demonstrate that if children from small families went to nursery aged 6-11 months they were substantially less allergy-prone than if they went later. The allergy risk was highest for only children who did not go to nursery until they were over two years.
Researchers in Colorado have recently tackled this subject from a different angle completely, analysing house-dust for the levels of bacterial endotoxin – substances that come from certain kinds of bacteria and which have a powerful effect on the immune system. If the house-dust contained high levels of endotoxin, babies brought up in that house were less likely to give positive skin-prick tests to common allergens such as cats, milk or house-dust mite. The babies from very clean houses, with low levels of endotoxin in the dust, were the ones with allergic reactions. (Fortunately, it is possible to have a dusty house with very little house-dust mite)
The hygiene hypothesis, as it is known, could also explain the strange history of hayfever. For the first century of its existence, hayfever was a disease of the urban upper classes, only gradually working its way down to the poor and to rural communities: this fits in well with the gradual spread of more hygienic ways of life. In most parts of the developed world today, it shows no class distinctions, but recent investigations have found a lower rate of hayfever among children raised on a farm with animals compared to children living in the same villages without farm animals.
In addition to greater hygiene, the following aspects of modern living appear to promote an allergic tendency in children:
• smoking by the mother during pregnancy and after, which may boost IgE levels
• breathing nitrogen dioxide from gas cookers, and formaldehyde from various household sources ; exposure to substances called phthalates, from plastics, may also be important; the poor ventilation of many modern houses, and the far greater time spent indoors aggravates the problem by increasing exposure to these irritants, and to allergens such as house-dust mite and moulds.
• taking antibiotics during the first two years of life
• bottle-feeding and/or abrupt and early weaning
• exposure to a virus called Respiratory Syncytial Virus (RSV) during infancy, which provokes an IgE-reaction (37)
• caesarean births; simply being born in a hospital might also raise the risks by exposing newborn babies to Staphylococcus, which adversely affects the immune system.