5.FB.1. Introduction

An allergy is an exaggerated reaction by the patient’s immune system to an allergen that triggers different reactions in several organs and tissues. Allergy has developed into a major health concern in Europe, with over 80 million people affected by some form of allergy and two-thirds of them stating that allergy presents a serious handicap in their day to day life. Different expressions of allergic disorders include allergic rhinitis or hay fever, asthma, atopic dermatitis - eczema - and other skin complaints, conjunctivitis, food and drug hypersensitivities. Allergens are usually proteins, that get in touch with the human organism through food, airways and contact with the skin or the mucosae.

Atopy is a personal and/or familial tendency to, usually in childhood or adolescence, become sensitized and produce IgE antibodies in response to ordinary exposure to low doses of allergens, usually proteins. As a consequence, atopic individuals can develop typical symptoms of allergic asthma, allergic rhinitis and allergic conjunctivitis or atopic eczema/atopic dermatitis.

5.FB.2. Data sources

The data presented in this section are:

- derived from papers published on peer reviewed journals

- GA2LEN

- EFA-European Federation of Allergy and Airways Diseases Patients

   Associations

- The SCALE strategy

- WP5: Clustering of European food allergy research

- World Allergy Organization

5.FB.3. The “allergy march”

This disease often progresses from atopic dermatitis to allergic rhinitis and then to asthma. This evolution, known as “allergy march”, needs to be carefully followed. Usually, the clinical symptoms of atopy appear early in life, persist over years or decades and often remit spontaneously with age (Figure 5.FB.1).

Figure 5.FB.1. Symptoms of allergic march

Allergic diseases can currently be managed effectively but not cured. Most of them are seldom lethal, but they can heavily affect the patients’ quality of life and have a considerable socio-economic burden, in terms of health care utilization, medication and missed school or work days. Allergic rhinitis is often underestimated by patients and underdiagnosed by physicians. However, it can evolve in asthma; thus, prompt diagnosis and treatment are required to stop the allergic march.

5.FB.4. Epidemiology of allergic diseases

Prevalence of allergic diseases

More and more people are developing allergic diseases and it is estimated that,

by 2015, one out of two Europeans will suffer from at least one form of allergy. Furthermore, allergic diseases are often underestimated, under-diagnosed and do not receive adequate treatment. Allergic diseases are considered “global” diseases not only because they are rapidly developing all over the world but also because they affect the body as a whole. Allergic diseases can arise at any age, although they more often begin during childhood. At present, one out of four European children under the age of ten is affected by a form of allergy. The problem of diagnosis and treatment compliance by health professionals is linked to the fact that allergic diseases require the health care system to ensure regular follow-up. An early and accurate diagnosis is crucial as some allergic diseases can be risk factors for further allergic reactions and asthma,.

There are still some enigmas in the epidemiology of allergic diseases. First of all, despite the quite homogeneous lifestyles throughout Europe, allergy prevalence among teenagers ranges from 3.7% in Greece, to 16% in Finland and up to 32% in UK. Secondly, among children, boys are more prone to develop an allergy, but this gap is balanced out during adolescence. Finally, office workers are more subject to allergies than outdoor workers. Data about the overall prevalence of atopic-related allergies among Europeans are few. At present, more than 80 million people across Europe are estimated to suffer from a form of allergy. Significant higher prevalence of atopy and allergic asthma was observed in the early 1990s among populations living in Western Europe compared to those living in Eastern European countries. Changes in lifestyle after the fall of the communist system were associated to an increasing trend of atopy and hay fever in former East Germany only 6 to 8 years after the Germany reunification. It has been hypothesized that a similar "converging" trend in the prevalence of allergic asthma and of bronchial hyperresponsiveness may take longer periods and may be observed in the next future.

5.FB.5. Risk and protective factors

The development of allergies is mostly linked to the immune system producing a particular kind of antibody known as IgE. For reason yet to be elucidated, allergic patients produce an excess of IgE in response to the exposure to substances that usually do not elicit any response in non allergic individuals.

Allergic diseases have a multifactorial aetiology, with both genetic background and environmental triggers playing a pivotal role in their development. The dramatic increase of the incidence of allergic diseases in Europe seen particularly in the latest two decades could be accounted to environmental factors, since it is very unlikely that genetic/hereditary factors could change in such a short period. However, the continuously increasing incidence of allergic diseases across Europe could be partially explained by the higher physicians’ awareness of these conditions, exposure to indoor and outdoor pollutants and, most of all, by the Western lifestyle. In particular, the reduced exposure to microbes seen in Europe in the last decades, due to the improved hygienic and social conditions, causes a significant increase of the incidence of allergic asthma, rhinitis and food allergies. This correlation is explained by the shift from Th-1 phenotype (the immune response that occurs during bacterial and viral infections) to Th-2 phenotype of immune response (the immune response causing allergies) by T–lymphocytes, a shift that occurs when infection rates decline.

Obesity also has been proposed to play a pivotal role in development of atopy. A recent study made in Great Britain reported an increase prevalence of atopic symptoms at the age of 42 in obese people. A meta-analysis including 12 studies examined the effect of high body weight during middle childhood on the outcome of subsequent asthma, showed a 50% increase in relative risk (RR 1.5, 95% CI 1.2 to 1.8). The combined results from nine studies that examined the effect of high birth weight on subsequent asthma had a pooled RR of 1.2 (95% CI 1.1 to 1.3) and concluded that children with high body weight, either at birth or later in childhood, are at increased risk for future asthma. Potential biological mechanisms include diet, gastro-oesophageal reflux, mechanical effects of obesity, atopy and hormonal influences. In addition, an increased prevalence of atopy (presence of specific serum IgE) has been found among obese women compared to normal weight women. However, the existence of the association of obesity with allergy or atopy and its meaning is still under debate (Plumb et al, 2007; Story, 2007)

There are contrasting data about a protective effect of breastfeeding on the development of atopy and allergic diseases. Exclusive breast-feeding reduces the incidence of allergic diseases at 18 – 47 ys of age (Bener et al, 2007). On the contrary, the Avon Longitudinal Study of Parents and Children (ALSPAC), performed on 2100 British children, reported a reduced incidence of wheezing at the age of 3 months in breast-fed infants with respect to bottle-fed ones, but no differences between the two groups were found regarding the incidence of atopy and asthma. As stated by the America Academy of Paediatrics, at present there are insufficient data to document a protective effect of any dietary intervention beyond 4 to 6 months of age for the development of atopic disease.

5.FB.6. Control tools and policies

Primary prevention

In many industrialized countries, the increase in the prevalence of allergic diseases has become a serious public health issue. If preventive intervention is to be at all effective, it would have to be applied early in life, most probably in early infancy. Unfortunately, our understanding of the natural history of the process of atopic and allergic disease is still very limited. The evaluation of risk factors and determinants is a necessary prerequisite for any effective intervention studies.

Interventions for primary prevention are aimed at a population that is still healthy although at risk. Unfortunately, all predictors investigated so far are insufficiently sensitive and specific. Therefore, possible preventive measures should be recommended only if they are applicable to the whole population, present no risk and have a low cost.

All exposure to tobacco smoke should be avoided, particularly during pregnancy and infancy, because maternal smoking during pregnancy is significantly associated to reduced respiratory function and recurrent wheezing in infancy and early childhood and the risk of developing IgE responses to food proteins early in life.

Since children with a positive family history for atopy in first-degree relatives are more susceptible to allergic sensitization, atopy and asthma, additional measures for primary prevention have been studied in this “high risk group” during the last decade. The majority of the studies investigating prevention during pregnancy have found no real evidence for a protective effect of any maternal exclusion diet during that time. The protective effect of maternal avoidance of potential food allergens (milk, eggs and fish) during the breast-feeding period is considered at best to be marginal. The use of hydrolysed formulas for atopy prevention has been extensively studied over the years in cases where the mother does not produce sufficient breast milk. Some studies indicate that in “high-risk” infants extensively hydrolysed formulas together with the avoidance of cow’s milk proteins and solid foods for at least four months in children has some protective effect. However, protection may only be related to the food proteins that were avoided but not for prevention of disease such as atopic eczema or respiratory allergy. A recent, large randomized prospective study (the German Infant Nutrition Intervention Study) reported that extensively and partially hydrolyzed formulas reduced the incidence of atopic dermatitis in infancy when compared to standard infant formulas.

Secondary prevention

The organization of health care should be reconsidered on a national and international basis in order to provide greater harmonization and effectiveness of health care systems and professional training in allergology. High quality assessment criteria must be introduced, together with scientific and evidence-based preventive measures and guidelines for ensuring effective diagnosis and treatment. Prevention requires a more precise identification of atopic individuals, even from the very first infancy - when possible - and a deeper knowledge of risk factors in the aetiology of allergic disorders. A deeper knowledge of the clinical course of allergies is also required to establish efficient prevention programmes on the general population. A better implementation of treatment guidelines requires more education of both patients and doctors that is crucial for the improvement of allergic diseases. The following measures have been documented to be effective: treat atopic eczema/atopic dermatitis topically, and possibly with systemic pharmacotherapy, to prevent respiratory allergy; treat upper airways disease (e.g. allergic rhinitis ) to reduce the risk of development of asthma; In young children already sensitized to house dust mites, pets or cockroaches, specific exposure should be reduced or abolished to prevent the onset of allergic diseases and finally, remove employees from occupational exposure if they have developed symptoms caused by occupational allergic sensitization.

5.FB.8. Future developments

Allergic diseases can have a heavy impact on the quality of life of affected people, besides increasing health care costs and lost productivity. The first step in dealing with allergic diseases is their prevention, mainly in atopic individuals. For this purpose, large and adequate multi-centric clinical studies are required. In addition, the definition of reliable and accurate diagnostic tools is important to identify the affected and at risk individuals to begin an early treatment. In Europe,,allergic patients are currently underestimated, improperly diagnosed and undertreated. Major efforts are needed to redress this situation: first by generating additional expenditure for health care systems for then reducing the cost of the allergenic care for society as a whole.

5.FB.9. References

Plumb J, Brawer R, Brisbon N (2007): The interplay of obesity and asthma. Current allergy and asthma reports 2007, 7:385-389.

Story RE (2007): Asthma and obesity in children. Curr. Opin. Pediatr. 19:640-4