Background to Allergic Diseases

Background to allergic diseases

Fact 1: 18 million people in Britain suffer from allergies
Fact 2: There are 5.1 million asthmatics in the UK, it kills 1,500 of them each year.
Fact 3: The NHS drugs bill for allergies is £1.07 billion a year
Fact 4: 1 in 3 children develop eczema before age four

The predisposition to the allergic diseases of asthma, eczema, hay fever “seasonal allergic rhinitis”, perennial allergic rhinitis (year-round hay fever symptoms) is inherited as a group, along with the tendency to food allergy and severe allergic reactions causing the life threatening emergency of anaphylactic shock. About a third of humans (irrespective of race) inherit this tendency, but only a proportion go on to develop clinical disease. Asthma, eczema and hay fever are very rare in rural third world countries and were also rare in the UK and Europe until mid-Victorian times.

Babies with one affected parent have an approximately 50% chance of inheriting the tendency - The risks for one to get allergies when both parents have a problem exceeds 80%. Many doctors therefore recommend that preventative measures are taken in early life for babies with a strong family history – possibly the most important is that pregnant women should not smoke.

There are a number of factors in our developed lifestyle that has caused an increase in these diseases, so there has been a genuine increase in their frequency – a tendency which has been accelerating over the last twenty years. Some of these factors are not yet understood, but one is increased exposure to allergens in the home. There is evidence that exposure to these allergens in the first few months of life, possibly associated with decreased rates of prolonged exclusive breast feeding, is important in priming the baby for developing asthma and/or eczema later in life.

Eczema commonly starts soon after birth. Over half will grow out of it, but half will go on to later develop asthma or rhinitis. Food allergy is quite common in the first year or two of life, but the overwhelming majority of early food allergies are outgrown, often within a matter of months. Asthma often becomes evident between three and five years of age. Again, many sufferers will effectively grow out of it by puberty. Inhalant allergies (pollens, house dust mites, pets, etc) become increasingly more important than foods after three.

Important Warning: There is no such thing as a blood, hair, or other test that can accurately predict food allergy or intolerance. Do not be fooled into paying for such tests commercially – Not only will you be throwing away good money, but doctors report cases of malnutrition caused by diets based on some of these false claims.

Spring-time hay fever is due to tree pollen allergy. Patients with summer hay fever, or hay asthma don’t need telling their symptoms are due to grass pollen. Autumn symptoms are related to the seasonal release of mould spores.

Tips for Hay fever sufferers
Pet allergy is usually obvious, but can cause continual symptoms, as sometimes can moulds growing in damp houses.

The single most important allergy causing perennial (or year round) symptoms is that to house dust mites. At least 85% of patients with year round asthma or rhinitis are house dust mite allergic, whether or not they also have other allergies. Rubbing house dust mites into the skin is clearly important in some cases of eczema, especially in infants and children, but the extent of this problem is less certain. For more about mites and their allergens.

Medical research shows that allergen control measures can make a real difference to exposure levels, reduce symptoms and objective measures of disease activity, and the need for drug treatment. For more about what you can do at home.