Which are the most frequent allergic diseases and why are they increasing in recent years?

Allergic diseases, be they respiratory or caused by food or drugs, are increasingly frequent in recent years, mostly in western countries. One of the primary causes is most certainly the “western lifestyle” - the greater part of the day is spent in a closed environment that is often polluted by tobacco smoke and other chemical agents, with no fresh air from outdoors where the air we breath is polluted by traffic exhaust. Another important factor that encourages the increase of this pathology is also the gradual decrease of infections especially in childhood. As a matter of fact, it is thought that the immune system of modern man, lacking the stimuli of infectious agents such as bacteria and mycobacteria, but subject to the stimuli of numberless allergenic substances, does not produce protective antibodies, but compensates instead by producing IgE, the antibodies that mediate allergic reactions. Clinically, if food allergies mainly cause urticaria and angioedema, the aeroallergens instead, carried by pollens, mites, dandruf and mould, mainly cause respiratory symptoms such as rhinitis and asthma. Lastly, some drugs can cause a many-sided symptomatology, ranging from spiloplania to anaphylactic shock, in sensitized individuals.

How do allergic reactions take place?

The IgE, the antibodies I mentioned before, produced excessively by the immune system of allergic individuals, bind with certain inflammatory cells, in particular those defined “mast cells”, which are real “bombs” that can “explode” if the allergic reaction is triggered. Let me describe what takes place in the respiratory system, which is certainly the organ that is most involved in allergic reactions presenting clinical symptoms such as rhinopathy (itching in the nose with prolonged sneezing and rhinorrhoea), asthma and its equivalents (extremely troublesome, intense, protracted coughing). The mast cells are present in the mucous of the airways with IgE bound to particular receptors on the cell membrane. As soon as the sensitizing allergen, whether it be seasonal (for example those released by the pollens of Gramineae, Parietaria, Birch and Olive) or the perennial type (mites such as Dermatophagoides, cat and dog dander etc.) penetrates into the airways with the air inhaled, it interacts with these antibodies. This triggers an antigen-antibody-IgE reaction that in turn triggers the very explosive reactions I mentioned before. The mast cells release various pro-inflammatory chemical mediators. Among these are preformed ones such as histamine, which are stored within the cytoplasmic granules of these cells. Other mediators such as cysteine-leukotriene, prostaglandin and tromboxane are synthesized from scrap. All these substances act on one hand by directly causing airway inflammation and on the other hand they also attract other inflammatory cells such as eosinophils, macrophages, lymphocytes etc. When the latter reach the site of the allergic reaction, they magnify the inflammatory effects which become clinically evident with sneezing, coughing and asthma.

Spring is a troublesome season for those who suffer from allergies. Why is this the case?

For many a century spring has been the most traditional season for the onset of respiratory allergies. These involve the respiratory system and often the eyes too, with conjunctivitis. These are, as we have already stated, the so-called seasonal allergies, which arise when pollens ( equivalent, broadly speaking, to human sperm cells) of some herbs (Gramineae and the Parietaria, Urticaceae family, present in Naples and in Campania) or trees (Olive, Birch etc.) are released in the atmosphere in order to guarantee the reproduction and the continuation of the vegetal species. Well, once these pollens come to rest on the conjunctiva or on the nasal or bronchial mucous tissue of passers by, they rapidly release their protein content; if this contains allergens and if the individual is allergic, the reactions we have described will be triggered. It must however be said that spring is not the only season that carries allergic reactions since other plants, for example those belonging to the Composite family (Absinth and Ambrosia) release their allergenic pollen in autumn. On the other hand even the Gramineae, besides the Parietaria, can pollinate again in autumn. There are also some trees, such as the Cypress, which release pollen in winter, causing winter pollinoses, with rhinopathies which resemble those caused by viruses, while they are of an allergic nature instead. Another point we must consider is the role played by air pollution in cities with heavy traffic. It has been proved that the agents of urban pollution (dust, ozone etc.) increase the effects of the allergens by increasing their allergenic power or by enhancing their penetration into the airways by means of their pro-inflammatory action. It is thus evident that those who suffer mostly from pollinoses are city dwellers and on the other hand the periods characterized by clinical symptoms are becoming longer, and they are not limited anymore to the season in which the allergenic pollen is present in the atmosphere.

Can the onset of allergic diseases be forestalled?

Prevention is one of the most important stages in the attempt to decrease the onset or severeness of allergic diseases. Since the topic is very vast, I will only state that allergies resulting from seasonal pollens can be forestalled only by moving from the area where allergenic pollens are present. It is obvious that the majority of people find this hard to do. Concerning chronic allergies, especially the most widespread ones caused by house dust mite allergens, much can be done today by using appropriate coverings around mattresses, doing away with carpeting and cuddly toys and so on. It is then essential to stop smoking. It has been proved that smoke, even passive smoking, enhances the onset and exacerbation of allergic diseases.

Is it true that allergies change with time?

Allergies present a tendency to recede during certain stages of life and to increase during others. For example childhood asthma often tends to recede at puberty while on the contrary it can arise or worsen in menopause. Many are the reasons behind these events and not all of them have yet been identified. Such cases are caused by hormonal triggers besides anatomical peculiarities, as happens in puberty with the increase in the bronchial calibre. It is also said that allergic diseases tend to recede after the age of fifty and sixty. This is only partly true. As a matter of fact, some allergies, such as bronchial asthma arise in adulthood in some patients, at times even in those who had never suffered from it previously. It must however be stressed that even when the clinical symptoms recede or disappear completely, as happens, for example, in puberty, there however remains, in the allergic individual a certain degree of “aspecific” hyperreactivity in the organ that has undergone shock, in our case the airways, and this predisposes new crises. This means that asthma can reappear if these individuals, feeling strong without symptoms and thus forgetting their previous suffering, expose themselves to high concentrations of allergens or other agents that irritate the airways.

How do you cure allergic diseases?

If, despite all attempts at prevention, allergic diseases set in with more or less severe clinical symptoms, it is necessary to resort to the appropriate drugs. Today these enable us to treat patients adequately and to make a decided improvement in the quality of life of those who suffer from such diseases. In the drug context we must differentiate the symptomatic ones, such as antihistamines for rhinitis and B-2 adrenergic bronchodilators for asthma, both short acting ones (salbutamol, terbutaline, phenoterol) and long acting ones (formoterol and salmeterol), from drugs defined “basic”, which can reduce the allergic airway inflammation. Corticosteroids rank first among the latter (budesonide, beclomethasone, flunisolide, fluticasone, mometasone etc), especially those that can be administered by inhalation (nebulizers). Among useful drugs in the treatment of asthma we must also consider the antileukotrienes (montelukast and zafirlukast), the anticholinergic ones (ipratropium and oxitropium bromide), and so on.

Is it true that anti-allergic vaccines are often ineffective?

The use of allergen extracts in specific immunotherapy (SIT), incorrectly defined “antiallergic vaccines”, has been currently reduced as compared with the past. Despite the scientific reasoning behind subcutaneous administration of SIT, the use of this method is not widespread since it must compulsorily be administered by specialized doctors in a hospital environment that is equipped for possible emergencies such as anaphylactic shock, though these cases are luckily quite rare. The necessity to be vaccined weekly at least during the first months and then monthly for 4-5 years, with the need to wait awhile in hospital after the injection, discourages many from starting this treatment, especially when the symptoms are limited to brief periods in the course of the year. We must also say that the sublingual use of SIT is spreading. Since SIT however represents a “hyposensitizing” remedy and not a “desensitizing” one, it must be combined with drug treatment. More immunologic therapies against allergies will be available in the years to come. Among these are anti-IgE - particularly active in reducing bloodstream IgE, these will soon be on sale.

Can one heal from allergic diseases or do patients have to “put up with them” for life?

This is the most frequent question asked by those who suffer from allergies and unfortunately we are forced to answer that these diseases cannot be cured, due to their constitutional nature. But if the appropriate prevention and drug treatment is scrupulously and regularly followed, you can reach an absence of symptoms. But as we have already stated before, in allergic diseases “where there’s smoke there’s fire” even when clinical symptoms are absent for years. This means that even when the patient feels well, he must always watch out, steering clear of exposure to allergenic triggers or other airway irritants, in order to avoid the reappearance of a pathology that despite its silence, has not disappeared permanently. Persistent bronchial asthma patients often make the mistake of curing the symptoms when these appear, by using short acting bronchodilators. The irregular use of anti-inflammatory drugs in such cases unavoidably leads to a deterioration of respiratory functions, the process becomes chronic and is often associated with irreversible reshaping of the airways.

Translated by interpres sas