Spring Allergies

by Renato Alberto Meduri

The immune system's wrong responses.

THE TWO LIFES OF PHLOGOSIS
The microbial and viral pathogenic agents are recognized, and activate the so-called path T1 by producing antibacterial and antiviral antibodies. Allergens, like pollen or mites, for example, are recognized by Th2 and induce the creation of immunoglobulins and stimulate Mast cells, eosinophilia (producing leucine and histamine). With the activation of Th1, there is also interferon production which inhibits the Th2 path.
In physiologic conditions, the T1 system, in charge of protecting bacteria and viruses, and the T2 system, appointed to protection from parasites and various antigens, are activated in a basically balanced manner. A reciprocal modulating effect is installed. Vice versa, in the case of an allergic subject, the T2 system has genetic characteristics which give the subject an excess of responsive capacity. With time, such system will entail abnormal responses, that are excessive in regards to the agent in cause, inducing inflammatory diseases called allergies.
The IgE defensive proteins produced on demand by the Helper T2 cells of B lymphocytes, stimulate special defensive cells called Mast cells, inducing the release of excessive quantities of a substance which, if adapted, protects us from parasites. But, if it is excessive, it will instead create an allergic phlogosis characterized by swelling, mucous secretion, irritation. The conjunctival mucous which is exposed mucous can become a target organ of allergens. The molecule in question is the histamine, the same one that creates the classic itchy hive after a mosquito bite. The allergic manifestation generally involves the skin, the ocular, respiratory or gastroenteric mucous membrane: dermatitis, conjunctivitis, rhinitis, bronchitis, colitis are possible clinical manifestations. It is particulary dramatic when the response is extreme, involving the whole body: hypertension, tachycardia, and choking because of acute swelling of the laryngeal mucous, paleness, hypothermia, unconsciousness. This is called anaphylaxis or anaphylactic shock.
More and more allergics
But this does not justify the increasing rate of allergies: 12% of the industrialized population suffer from allergies with a trend of progressive regular increment. Some studies have attributed this to home, urban and agriculture pollution: mites, engine waste, industrial waste, etc. In fact, it is unquestionable that any irritating stimulus makes the skin and mucous membrane more responsive, creating an allergic response. However, the overall polluting elements have, in the Western world, progressively reduced in the last 20 years so to identify pollution as the main cause for increasing levels of allergies is disputable. One hypothesis suggests an unforeseeable cause to increasing allergies: excessive hygiene. Cleaning products, water disinfection, food preservatives, and the increasing use of antibiotics have gradually reduced bacteria ad viruses. Such situation entails that, from birth, memorization and activation stimuli of the T1 lymphocyte system are reduced compared to the past, so the system adopts a minority position in comparison to the more stimulated T2 system.
For the normal subject, there are no particular consequences, but for subjects who have an overactive Th2 system, the lack of Th1 increases such overactiveness and induces allergic pathologies. In other words, the genetic predisposition can manifest itself more easily as a disease when there are favourable environmental conditions.
Are moms guilty?
Antonella Murano, allergist in the Pediatrics Department in Padova's hospital establishment, has demonstrated that allergic mothers' milk has a different composition than "normal" mothers.
In fact, maternal milk contributes to the maturation of the immune system of the newborn increasing the number of Th1 lymphocytes, thanks to the wealth of A immunoglobulins, cytokines, polyunsaturated fatty acids that are secreted. Allergic mothers' milk, however, is poor with such nutrients. The newborn's immune system begins immediately to receive unbalanced input: chances for allergies are increased.
The world of allergens
All substances can give allergies in various ways:
a) inhalation: pollen, dermatophagoides, spore fungi and epidermic derivatives of animals;
b) ingestion: food, chimical and pharmaceutical substances;
c) injection: pharmaceutical products and venoms;
d) contact: chimical and pharmaceutical substances for topic use, cosmetics, substances of vegetal origins.

MOST COMMON ALLERGENS
Pollen
Pollen are fine dustlike grains discharded from vegetal sources during springtime. But, not quite always in the spring: some pollen like those of cypress trees are discharged as early as December. In recent years, it has been observed an increase of early pollen because of herbaceous species with summer bloom. Beyond these phenomenons, during spring season, the pollen concentration in the air is higher and this justifies why these allergies are seasonal.
Mites
Microscopic animals of very few microns love the home environment: beds and carpets are their preferred refuge. They feed like gluttons on our leftovers: desquamated skin, dandruff, hair, etc. Our sweat creates conditions for growth. Unfortunately, their discharged excrements in the air are powerful allergens. When we say that we are allergic to home dust, we are simply allergic to the excrements of these very tiny animals.
Pets
Pets urinate, have dead skin flakes and flees. Through hair these waste come into contact with our skin and with our mucous membrane, and are powerful allergens. Recent studies have demonstrated that children who live with dogs, cats, or animals in general, have less probabilities to develop allergies. The reason was identified in some bacteria found in dogs and cats. Endotoxins produced from such germs are characterized to attenuate lymphocytic responses.
Mould
In basements, woodsheds, but also in the home, in humid corners or on food that is not well preserved, there can be found a variety of mycetes that are characterized for developing spore, frequent cause of allergies. The air in some work environments is particulary rich with spore: libraries, paper mills, farms, greenhouses, dairies, etc.
New allergens all the time
A recent study reported a new intolerance: the rubber elongation factor of rubber trees as the major allergen in latex (in protective gloves, for example). Such protein adheres to the corn dust used to lubricate gloves, it is disseminated in the air reaching conjunctival, nasal and lung mucous membranes. Another emerging phenomenon is "cross" allergies. It was demonstrated that the presence of some form of allergy predisposes to other allergies. For example, allergy to latex, which was discussed above, may increase risks for allergies to bananas or kiwis; others who are allergic to pollen can more easily be susceptible to the cherry, tomato, fennel and watermelon.

Atopy
Some subjects demonstrate a strong reaction to molecules that are not found in vegetal or animal allergens, which are called haptens. In such subjects, haptens induce an excessive synthesis of IgE and proinflammatory cytokines. This genetic situation increases allergies significantly. A characteristic of children with atopy would seem to be milk crust.

THERAPY
The main pharmaceutical product for treating allergies is antihistamine.
It works by counteracting the effects of histamine on a receptor site preventing the inflammatory response. The secondary effect, which is not always pleasant, is drowsiness. The antihistamine represents nevertheless a good solution for rapid and efficient action, for external use: collyrium, inhaling spray, ointment.
Corticosteroid
This provides an anti-inflammatory action that is more generic, blocking or reducing the lymphocyte response and also of particular lymphocyte typical of allergic phlogosis like eosinophilia. This product may be used alone or together with an antihistamine. Prolong use may cause stomach problems, high blood sugar, cataract and endocrine problems; it proves however particulary useful in emergency situations.
Cromolyn sodium
This is a type of medicine that prevents the release of histamine. It can be inhaled through the mouth or nose. There are no important secondary effects so prolong use is possible. This may also be a treatment for small children.
Cyclosporin: inhibition of T lymphocyte
This is an anti-proliferating pharmaceutical product which blocks replication of cells and, therefore, also those causing an allergic response. It is indicated most of all when other immune pathologies are involved.
Monoclonal antibodies
These are proteins obtained in labs. They are binded to immunoglobulins E (IgE) blocking every successive activation. The treatment products mentioned above are for symptomatic therapy, that is that they work only during the time the product is administered: they eliminate symptoms, but they do not cure the disease.
Vaccination
In special cases, when it is possible to exactly identify the substance that creates the allergic situation, it is possible to resort to specific desensitisation even with numerous offending allergens. This strategy, however, does not always have the desired success.
Various therapeutic strategies
As it is recognized that in the allergic subject there subsists a responsive redundancy of the T2 system, it is justified to associate symptomatic therapies, mentionned above, to a stimulus of the T1 system which, if adequately prolonged, allows balanced relationships and therefore the normalization of the T2 system's response: the subject becomes less allergic. A simple lab test: the dosage of IgE allows treatment control. This type of vaccination improves generically the defense capacity of the mucous membrane surface, hence protecting it from bacterial and viral aggression.