Allergenic pollen records (15 years) and sensitization in patients with respiratory allergy in Thessaloniki, Greece

Authors


Dimitrios Gioulekas
Pulmonary Department
G. P. Hospital ‘G. Papanikolaou’
Aristotle University of Thessaloniki (A.U.Th.)
Mitropolitou Iosif 5
Thessaloniki 54622
Greece

Abstract

Background:  Very limited allergenic pollen records exist in Greece so far; moreover, there is a lack of investigation on patient sensitization. The above data are necessary for respiratory allergy diagnosis and treatment worldwide.

Methodology:  Daily records and identification of 16 airborne pollen species were made using a Burkard trap (1987–2001). Skin sensitivity to 13 most common pollen extracts was investigated, in a sample of 1311 asthmatics with atopy, admitted to the Out-Patient Clinic for Asthma (1990–2001). Skin sensitivity to 55 allergens, including 13 pollen extracts, was detected by skin prick test.

Results:  The following pollen concentrations were recorded: cypress (24.9% of the total), oak (20.8%), wall pellitory (13.6%), olive (9.1%), pine (8.9%), grasses (6.3%), plane (5.4%), hazel (3%), goosefoot (2.5%) and poplar (1.4%). The respective percentages of birch, ragweed, mugwort, willow, alder and elm were lower than 1%. The highest counts of airborne pollen grains were detected from March to June. Regarding patient sensitization, sensitivity was detected to: grasses in 530 patients (40.4%), olive 417 (31.8%), goosefoot 240 (18.3%), wall pellitory 201 (15.3%), mugwort 198 (15.1%), plantain 194 (14.6%), cypress 166 (12.7%), hazel 126 (9.6%), pine 122 (9.3%), poplar 111 (8.4%), plane 107 (8,2%), oak 99 (7.6%) and to birch 89 patients (6.8%). The sensitivity to pollen grains displays preponderance (57.9%) to males.

Conclusions:  For the first time in Thessaloniki, Greece, 15-year allergenic pollen records were conducted. Clinical observations confirm that the pollen mainly implicated in respiratory allergy symptoms are grasses, olive and wall pellitory.

Epidemiologic surveys support that asthma affects 5–30% of children and 2–30% of adults (1, 2). This wide range of intersurvey fluctuation is mainly the result of different geographic distribution and is due to the use of different criteria among studies. Nevertheless, the prevalence of asthma in children, even in the absence of smoking as risk factor, is higher compared with adults. Rhinitis affects 40% of the population; 30% of it concerns seasonal and 10% perennial rhinitis (3). Many studies refer to the interrelationship between asthma and rhinitis; in one report asthmatic patients were asked to fill in questionnaires about rhinitis and the results revealed that asthma occasionally coexisted with rhinitis up to 98.9%. The authors characterize it as ‘a chronic allergic disease of airways’ (4).

Pollen allergy (hay fever, pollinosis) is a common disease caused by hypersensitivity reaction of the respiratory tract and eye conjunctivae to pollen grains. It concerns seasonal allergic manifestations affecting patients during plant pollination season and includes allergic rhinitis, allergic conjunctivitis, allergic bronchial asthma and less frequently urticaria. The characteristic of seasonal allergy is the recurrent occurrence of symptoms.

The term respiratory allergy refers to clinical manifestations of both upper and lower respiratory tract due to allergy. Patients experience symptoms only during the circulation season of aeroallergens to which they are sensitive.

It is well established that inhalation of pollen grains induces respiratory allergy symptoms in sensitized individuals. These are clinically manifested as rhinitis, rhinoconjunctivitis and bronchial asthma. Dr Sir Charles Blackley, in the nineteenth century for the first time, laid the foundations of the diagnosis and appropriate treatment of seasonal allergic diseases (5); a lot of his observations are still being used by a lot of researchers to date (6).

Many different species of pollen grains disperse in the atmosphere and they are correlated with the flora of each region. Pollen grains are highly specialized microspores of the male structure of the plant flower, necessary for the reproduction of plants (7, 8). Their atmospheric presence is strongly influenced by meteorologic conditions in each area (9). The recording and forecasting of pollen dispersion in the atmosphere attract the majority of scientists and specialists interest for several reasons. In medicine the main aim of scientific research is the creation of pollen calendars, used for the estimation of the flowering and pollen circulation season during which clinical symptoms occur and, moreover, the forecasting of different allergenic pollen species in various regions.

Aim of the study

The aim of the study was the creation of a database including long-term records made on a daily basis and the identification of pollen with allergenic interest in the area of Thessaloniki, Greece (creation of pollen calendar). It was considered necessary to detect the skin sensitivity of asthmatic patients to pollen, which are the most frequently implicated to respiratory allergy symptoms (10).

Study area

Thessaloniki is an old city that celebrated its 2300-year anniversary of foundation in 1984. The city is built in the heart of Thermaikos Gulf in the Aegean Sea and its geographic location is 40°37′N and 22°57′E. Nowadays, Thessaloniki is an industrialized modern city of more than one million inhabitants, the second biggest city in Greece, the cultural and economic center of Macedonia and northern Greece and an important seaport.

In the north-east of Thessaloniki there is a large forest of pines, cypresses, cedars and oaks, called ‘Kedrinos Lofos’. In the western side, where the industrial zone is well developed, the city is in contact with extensive fields of cultivated cereals. The east part of the city is close to grass areas and olive trees, neighboring on the peninsula of Chalkidiki. In the south the city borders on the Mediterranean Sea.

Material and methods

The study design included:

  • 1Daily records and identification of more than 40 pollen grain species belonging to different plant taxa. Selection of the 16 most significant for presentation, as far as their allergenicity is concerned.
  • 2Creation and presentation of pollen calendar for the most allergenic pollen.
  • 3Detection of skin sensitivity to allergenic pollen in asthmatics.
  • 4Detection and presentation of start, peak and end dates of pollen circulation season.

Records, identification and presentation of pollen in the atmosphere of Thessaloniki

This study began in September 1986, when the Burkard volumetric spore trap was installed in the center of Thessaloniki. Daily sampling of airborne pollen started on February 1, 1987 and continues until today. In this study, 15-year records are being presented, a period long enough for the creation of pollen calendars in an area (11).

The records of pollen grains were made using a Burkard 7-day recording volumetric trap, equipment standard for aerobiologic sampling worldwide (7, 8, 12, 13). The trap was placed on the roof of a six-floor building in the center of Thessaloniki and at a height of 25 m above the ground, collecting pollen grains in the ambient air throughout the study (7). The Burkard trap is a compact unit with built-in vacuum pump, designed to sample airborne particles, such as pollen grains, continuously for periods of up to 7 days without attention. Particles are impacted on adhesive-coated transparent plastic tape supported on a clockwork-driven drum. The drum moves 2 mm/h and thus the concentration of airborne particles can be calculated hourly. The vacuum pump draws about 10 l of air/min through a thin orifice, a function that is not influenced by weather conditions. The tape is coated with a special type of silicone (‘Gelvatol’ silicone grease, Burkard Manufacturing Company Ltd, UK). The drum makes a complete revolution after a week; then, the tape is taken, it is cut into seven pieces – each piece representing a single day of sampling, that is 48 mm of tape and these are mounted on slides with glycerin and saffranine under cover slips. Recognition and counting of pollen grains is performed under a light microscope (40×). Pollen grain counts are expressed as pollen grains per cubic meter of air (7, 10, 12).

Data are presented as average values per 10 days in accordance with the International Association for Aerobiology (11). Sometimes these values are expressed as moving average values per 10 days (running means).

Running means or moving average values for a specific period of time is a statistic technique used for presentation of values with great variation, in order that their variance is smoothed. In this way, we are able to more easily observe the general trend, which is more valuable than the daily variation of values. In the occasion of airborne pollen, decrease of intervariations in recorded values allow us to predict the general trend of aeroallergen concentrations, a measure much more significant than the mere daily fluctuation.

Creation and presentation of pollen calendar

Data of pollen grain records were inserted in an automated computer worksheet and processed with Microsoft Excel for Windows. The pollen calendar was created according to the methodology referred to ‘Allergenic pollen and pollinosis in Europe’ (11). Pollen grains were expressed in average daily values and then, in our occasion, as average daily values per 10 days, for the 15-year period (1987–2001). They were presented on a specific scale, each level corresponding to a particular amount of pollen grains. These levels were: first: total sum of one to two pollen grains per 10 days, second: three to five pollen grains, third: six to 11 pollen grains, fourth: 12–24 pollen grains, fifth: 25–49 pollen grains, sixth: 50–99 pollen grains, seventh: 100–199 pollen grains, eighth: 200–399 pollen grains, ninth: 400–799 pollen grains, 10th: 800–1599 pollen grains and 11th: a sum of more than 1600 pollen grains per 10 days. In this way, all interactions between external factors and pollen concentrations were significantly decreased, enabling us to compare different pollen species concentrations throughout the year. The daily pollen grains average values per 10 days were presented for the 15-year period (1987–2001); they concerned only the main pollen season, that is, from February 1 to September 30.

Detection of skin allergic sensitization to pollen extracts in asthmatic patients

The study refers to 1744 patients admitted to the Out-Patient Clinic for Asthma of the Pulmonary Department of Aristotle University of Thessaloniki in the General Hospital ‘G. Papanikolaou’ from January 1, 1990 until the end of 2001. The patients included in the study were necessary to have presented annual periodicity, seasonal occurrence of symptoms and/or worsening of respiratory allergy symptoms. The examination of patients included:

  • 1Filling in a questionnaire of 200 questions specific for asthma. This can be electronically processed, thus enabling us to examine the relation between skin allergic sensitization (skin prick tests, SPT) and the onset of clinical symptoms.
  • 2Clinical examination.
  • 3Spirometry and, in some cases, bronchial challenge test with metacholine or histamine.
  • 4Chest X-ray film.
  • 5Specific IgE (detected only in some cases).
  • 6Skin tests.

Skin tests were performed by a modified skin prick technique. The most common inhalant and food allergens were used, a total of 55 extracts, including 13 pollen extracts. The selection of pollen species was made according to the local vegetation and to expected sensitization, as documented by past studies made in our country, Europe and the USA (10, 14–26). The allergens were either isolated or in groups. All the allergens were produced by Allergopharma J. Ganzer KG (Reinbek, Germany). The pollen extracts used were: grasses family – two mixes (f. Poaceae), olive family (c. olive, ash, f. Oleaceae), nettle family (c. wall pellitory, f. Urticaceae), cypress family (c. cypress, juniper, cedars, f. Cupressaceae), composites family (c. ragweed, mugwort, f. Asteraceae/Compositae-Tubuliflorae), plane family (c. plane, f. Platanaceae), goosefoot family (c. goosefoot, f. Chenopodiaceae), hazel (Corylus spp., f. Corylaceae), plantain (f. Plantaginaceae), pine (f. Pinaceae), poplar (Populus spp., f. Salicaceae), oak (Quercus spp., f. Fagaceae) and birch (Betula spp., f. Betulaceae). Skin positivity was recorded 15 min after the test and the wheal and flare reactions were impressed on transparent cellophane. Positivity was expressed in wheal diameter >3 mm and flare diameter >10 mm compared with negative and positive controls (6, 10, 27, 28).

Presentation of start, peak and end of pollen circulation season

As the start of pollen circulation season, we regard the time when the amount of pollen grains count up to 5% of total average amount of pollen grains recorded during the previous years, that is, the 15-year period (1987–2001). The peak is considered to be the specific day on which the greatest number of pollen grains was recorded – always compared with the 15-year period of sampling. Likewise, we consider the 95% to be the end of pollen circulation season, also compared with the average values of pollen grains records of the previous years (29, 30).

This ‘prediction system’, called 5–95%, actually takes into consideration not only the time when pollen begin to disperse in the atmosphere, but also the time when the first clinical symptoms – because of them – occur. Therefore, this appears to be the clinical onset and end of the pollen circulation season, which appeals to the beginning and end of the clinical symptoms of allergic patients with moderate sensitivity to pollen allergens.

Results

Aerobiologic records of pollen

More than 40 pollen species were recorded and identified during the 15-year period of sampling. However, only 16 of them, the most common implicated in respiratory allergy symptoms worldwide, are being presented in this study. The airborne pollen records in the area of Thessaloniki during the 15-year period (1987–2001) are presented in Table 1. Significant variations are observed among different species each year. The annual average pollen total concentration is displayed in Fig. 1, in moving average values per 10 days (running means) for the 15-year period of records. The concentrations of each pollen species (moving average values per 10 days) are presented in Figs 2 and 3. In Fig. 4, the pollen calendar including all recorded aeroallergens is displayed.

Table 1.  Total annual concentrations of each pollen species, annual sum of all species concentrations and their percentages (%) for each one of the 16 pollen species recorded in the area of Thessaloniki during 1987–2001
Pollen species198719881989199019911992199319941995199619971998199920002001TotalAverage%
Cypress (Cupressaceae)64326589016191216304416341850177211533660262176511865406939 145261024.9
Oaks (Quercus spp.)1532254415931958157514655791078156815433693109131057422191132 657217720.8
Wall pellitory (Urticaceae)21727017142291513302134261437920012925231833322517175921 432142913.6
Olive, Ash (Oleaceae)1554092364071201139812264133891636133965923991490102214 3799599.1
Pine (Pinaceae)4036048055876599321111405661110511456961482267277914 0469368.9
Grasses (Poaceae)3654303984396032413463032678771267784195697967499296626.3
Plane (Platanaceae)4432832128726531828616450111734143318191528121085115675.4
Hazel (Corylus spp.)1003633012872471361901508037973435043025365646563103.0
Goosefoot (Chenopodiaceae)7715415025633315618812513445350138637837628139482632.5
Ragweed, Mugwort (Compositae)  1181332831761791641211691629320929713822421721.4
Poplar (Populus spp.)22920917818612684122109107132192422166510422091471.4
Plantain (Plantaginaceae)161837101033568357521271072961981291229820.8
Willow (Salix spp.)19863121754666293413773127736165943630.6
Alder (Alnus spp.)5314810852558841140107107676697895600.6
Elms (Ulmaceae)25163210424037292109479864356610410.4
Birch (Betula spp.)177147313854243565875129341494330.3
Total96846110683754468264843474745624578910 70016 47410 14423 52819 86612 951157 3259625 
Figure 1.

Ten-day moving average values of the total amount of pollen grains for the 15-year period of records in the area of Thessaloniki.

Figure 2.

Group of graphs I: Ten-day moving average values of eight pollen species for the 15-year period of records in the area of Thessaloniki.

Figure 3.

Group of graphs II: Ten-day moving average values of eight pollen species daily for the 15-year period of records in the area of Thessaloniki.

Figure 4.

Pollen calendar of 18 pollen species in summed 10-day average values for the 15-year period of records in the area of Thessaloniki. It is also presented the scale with the specific levels of pollen concentrations.

Detection of skin allergic sensitization to pollen

From a sample of 1744 patients examined for allergic sensitization to pollen, 1569 (90%) were born and lived in the area of Thessaloniki. The other 175 (10%) have lived in the study area for the last 10 years. Their average age was about 35 years old (6–68 years old) and average duration of asthma was 23 months (3 months to 10 years). Skin positivity to one or more allergen extracts of the 55 tested occurred in 1311 (75.2%) patients, while 433 patients (24.8%) had a negative reaction. About 552 of the 1311 patients reacting positively to skin prick tests were women (42.1%), whereas 759 (57%) were men. On the contrary, concerning the 433 patients having presented negativity to skin prick tests, 260 were women (60%) and 173 patients (40%) were men. The majority of patients with a positive reaction to pollen simultaneously presented a positive medical history and clinical symptoms, occurring mostly during March–May and, partially, July–August (Table 2).

Table 2.  Patient sensitization to 13 pollen, presented as percentages of the total 1311 patients with respiratory allergy examined. Distribution of sensitization to two sexes
Pollen speciesSensitization, n (%)Sex distribution
Men (%)Women (%)
Grasses (Poaceae)530 (40.4)285 (53.8)245 (46.2)
Olive, Ash (Oleaceae)417 (31.8)225 (54.0)192 (46.0)
Goosefoot (Chenopodiaceae)240 (18.3)135 (56.3)105 (43.7)
Wall pellitory (Urticaceae)201 (15.3)108 (53.7)93 (46.3)
Ragweed, Mugwort (Compositae)198 (15.1)112 (56.6)86 (43.4)
Plantain (Plantaginaceae)194 (14.8)115 (59.3)79 (40.7)
Cypress (Cupressaceae)166 (12.7)91 (54.8)75 (45.2)
Hazel (Corylus spp.)126 (9.6)73 (58.0)53 (42.0)
Pine (Pinaceae)122 (9.3)84 (68.9)38 (31.1)
Poplar (Populus spp.)111 (8.4)63 (56.7)48 (43.3)
Plane (Platanaceae)107 (8.2)68 (63.6)39 (36.4)
Oaks (Quercus spp.)99 (7.6)52 (53.0)47 (47.0)
Birch (Betula spp.)89 (6.8)57 (64.0)32 (36.0)

A total of 530 patients (40.4%) presented positive skin allergic reaction to grasses (Poaceae), 417 allergic patients (31.8%) to olive (Olea europaea), 240 patients (18.3%) to goosefoot (Chenopodiaceae), 201 (15.3%) to wall pellitory (Parietaria spp.), 198 (15.1%) to ragweed and mugwort (Compositae), 194 (14.8%) to plantain (Plantaginaceae) and 166 patients (12.7%) to cypress (Cupressaceae). Moreover, 126 allergic patients (9.6%) presented skin sensitivity to hazel pollen, 122 (9.3%) to pine (Pinaceae), 111 (8.4%) to poplar (Populus spp.), 107 (8.2%) to plane (Platanaceae), 99 (7.6%) to oak (Quercus spp.) and 89 allergic patients (6.8%) displayed skin sensitivity to birch (Betula spp.).

Start, peak and end date of pollen circulation season in the area of Thessaloniki

According to the ‘prediction system 5–95%’ (Table 3), seven pollen species begin their circulation season in February, one pollen species in March, six in April, one in May (Chenopodiaceae) and one pollen species in July (Compositae). The respective end of pollen circulation season was observed for one species in March (Alnus), for one species in April (Ulmaceae), for six in May, for four in June and for four pollen species in September. The highest levels of pollen grains in the atmosphere of Thessaloniki occurred for 13 species from February to May, whereas for the rest three species between June and August. May is the month with the highest concentrations of airborne pollen (five species) (Table 3).

Table 3.  Dates of start, peak and end of each pollen species circulation season, according to the ‘prediction system 5–95%
Pollen speciesStart (5%)PeakEnd (95%)
  1. In brackets, the concentration of each species is presented for the respective date. For 5 and 95%, these concentrations correspond to the sum of pollen grains adding up to the 5 and 95%, respectively, of the total annual amount of pollen, whereas for the peak it represents an actual daily value.

Cypress (Cupressaceae)February 11 (123)  March 5 (151)May 17 (2346)
Oaks (Quercus spp.)April 14 (109)   May 5 (78)June 10 (2080)
Wall pellitory (Urticaceae)  April 5 (70)   May 5 (101)June 29 (1335)
Olive, Ash (Oleaceae)  April 8 (48)May 28 (39)June 14 (908)
Pine (Pinaceae)March 31 (47)April 25 (27)June 19 (900)
Grasses (Poaceae)April 17 (33)May 26 (17)September 6 (628)
Plane (Platanaceae)  April 2 (26)April 10 (48)May 12 (495)
Hazel (Corylus spp.)February 20 (14)  May 4 (14)May 15 (271)
Goosefoot (Chenopodiaceae)May 27 (13)August 27 (7)September 24 (249)
Poplar (Populus spp.)February 15 (8)  April 6 (6)May 5 (143)
Ragweed, Mugwort (Compositae)  July 9 (9)August 17 (6)September 27 (166)
Plantain (Plantaginaceae)April 12 (4)  June 4 (2)September 11 (75)
Willow (Salix spp.)February 21 (3)March 15 (2)May 12 (58)
Alder (Alnus spp.)February 12 (3)February 22 (6)March 26 (55)
Elms (Ulmaceae)February 15 (2)February 24 (3)April 25 (38)
Birch (Betula spp.)February 12 (2) March 4 (2)  May 4 (33)

Discussion

All components of atmosphere do not present the same allergenic significance for human. Pollen grains have been studied as aeroallergens. Pollen allergy is involved with local vegetation and depends on the way and duration of exposure to aeroallergens, provided of course that there is a genetic predisposition to respiratory allergy (23, 31, 32). Many researchers relate the occurrence of respiratory allergy symptoms with the presence of pollen grains in ambient air; besides, it is well documented that inhalation of specific species of pollen grains causes clinical symptoms of respiratory allergy (5, 6).

Concentrations of airborne pollen in the atmosphere of Thessaloniki vary both for the annual total amount of pollen and for the annual values of different species for the 15-year period of records. This is not a rare incidence in the plant world; on the contrary, it happens every year and is due to several reasons. Therefore, it is necessary to obtain long-term records, so as to ensure the stability of predicted pollen grain concentrations in the atmosphere (11). Recorded pollen counts and their annual variability from 1987 to 2001 are presented in Table 1. Allergenic airborne species appear in the area of Thessaloniki only from the end of January to the end of September (Fig. 1). The highest concentrations of pollen were observed from the beginning of March until the start of June (Fig. 2); during that period, it is estimated that 81% of the total annual amount of pollen grains circulates in the air of the city.

A wide range of factors affects the production, dispersion and transportation of airborne pollen. It is widely documented that a favorable combination of air temperature, relative humidity and sunshine (‘growth degree days’ or ‘day degree units’) is needed by each plant to shed its leaves, flowers and fruits every year. As long as each plant is under these ‘excellent’ conditions for a minimum period of time, it is capable of reproduction (33). The exact number of pollen grains expected to disperse in the atmosphere and the duration of their circulation season in a specific region depend on wind direction and speed, rainfall height and duration and relative humidity during the flowering season (8). Hence, plant growth conditions may be reproduced in a laboratory; however, the conditions of pollen grain circulation in the atmosphere cannot be easily reproduced and seem to be specific for each different species. Moreover, the presence of pollen in ambient air is significantly influenced by inner functions of the plant's flower that have been referred to as the result of meteorologic parameter interactions (7). Many studies suggest that it is necessary to record and correlate the airborne pollen concentrations with the most important meteorologic parameters values (34). As annual intervariations can be really high, the average values are preferably used, for a period of sampling as long as possible (11). Thus, we used the average values of pollen concentrations (Table 1, Fig. 1) for the 15-year period of records (1987–2001), in order to ensure the production of safe results. An example of a great annual internalization can be seen between year 1987 (9684 total pollen grains) and year 1994 (5624 total pollen grains), concentrations almost half of those in 1987. Furthermore, in 1999, that is 2 years after a great fire in a large forest in our area, called ‘Kedrinos Lofos’ the highest values in the whole 15-year period were observed, despite the fact that about 60% of the forest's area had been burnt. Other researchers have also documented similar very significant differences in annual pollen counts (7). It is therefore concluded that nature follows its own rules, which are very hard for us to understand and explain thoroughly. It is strongly believed that more studies on ‘middle height’ atmospheric phenomena would draw safer conclusions about airborne pollen circulation.

As far as skin prick tests are concerned, they present a high diagnostic value, especially if combined with the patient's medical history. Positivity in skin tests is not usually observed to individuals lacking clinical symptoms (30). The method of modified SPT proves to be a reliable tool for detection of type I sensitivity in humans worldwide (10, 28, 35). In addition, the results can be stored in transparent cellophanes, enabling us to compare the results of the test at a given time with those at different periods or with other patient tests, even from abroad. The positivity of skin prick tests strongly correlates with bronchial hyper-responsiveness and other clinical aspects of bronchial asthma (36). Moreover, it is reported that skin prick tests are more reliable than detection of total and special IgE tests (35). In everyday medicine and asthma, the problem of respiratory allergy caused by pollen inhalation is very common. Few references exist in Greek literature about the incidence of pollen allergy and skin sensitivity in Greek citizens. Only very recent studies conducted in Greece refer to this problem (15, 25, 26). Our data concern a significant number of patients suffering from respiratory allergy (1744 patients), who live in the county of Thessaloniki, the area of the 15-year allergenic pollen study. The pollen species selected are regarded as mainly implicated in respiratory allergy symptoms in the most European countries (7, 8, 10, 12, 15, 20–22, 24). SPTs were performed during the period 1990–2001, which coincides with the period of pollen sampling. Among the 1744 asthmatic patients tested, 1311 (75.2%) of them presented skin positivity, whereas only 433 (24.8%) were negative to SPTs (Table 2). Similar results were taken both from Greek (26) and international studies (20, 21). According to every patient's medical history, they displayed increased asthma symptoms during the peak of pollen circulation season, that is between March and May. Furthermore, skin positivity to pollen was more often observed to men (759, 57.9%) than to women (552, 42.1%). This fact has been referred to by other scientists as well (15, 26) and is mainly due to genetic and hormonic factors, probably in addition to the impact of some external factors.

Frequency of SPT sensitization did not necessarily present a positive relationship with pollen grain concentrations in the air of Thessaloniki. Therefore, although many asthmatics presented a high SPT sensitivity (40.4%) to grasses (Table 2), pollen concentrations are only ranked at the sixth position of aeroallergen circulation in the area of Thessaloniki (Table 1). On the contrary, SPT sensitivity to oak was only 7.6% (Table 2), although it is the second most frequently detected aeroallergen in the region (Table 1). All these data are also documented by international references (6–8, 14).

By means of clinical observations – including SPTs – and medical history of patients, it was clearly observed that annual variability of pollen grains in the ambient air coincided with respective increase or decrease of allergic symptoms in sensitized individuals, whenever the latter were highly exposed to aeroallergens, as referred to references worldwide (7, 10, 14).

Forecasting of allergenic pollen season in an area is a crucial pursuit for all developed countries, in order to minimize clinical symptoms of patients suffering from respiratory allergy. This can be achieved through public announcements by the mass media (radio, television, teletext, telephone, Internet, etc.), aiming to protect allergic individuals. Thus, the total cost of disease treatment is finally reduced; in fact, it is assessed that this kind of massive protective treatment can decrease the number and frequency of visits to medical doctors by 50% (37). In this direction, we used the ‘prediction system 5–95%’ as the start and end, respectively, of the flowering season for each pollen species studied. Therefore, it is possible for every researcher to specify the onset and end of pollination season, during which the first clinical symptoms are expected to occur. Moreover, the particular day of the highest average pollen concentration for each species was detected. These predictions may vary significantly among different regions and for each plant species and they surely depend on previous years records (29, 30). The longest the sampling period, the more reliable and accurate the prediction of the ‘clinical’ start and end dates will be. Clinical start refers to the onset of symptoms of patients who live inside the city and present a moderate sensitivity. This had been examined with special questionnaires filled in by patients sensitive to allergenic pollen grains (cypress, wall pellitory, olive and grasses) and simultaneous comparison with the amount of airborne pollen in this area for the respective period of time (38). The knowledge of the start, peak and end of pollen circulation season for every allergenic pollen species is undoubtedly essential both for doctors and patients.

Conclusions

Records of 16 allergenic pollen species were conducted in the area of Thessaloniki during the last 15 years (1987–2001) and are presented in a pollen calendar, a fact very important for our city and country both from medical and biologic view. The most frequently recorded pollen grains in the region were of: 1) cypress, 2) oak, 3) wall pellitory and 4) olive.

Skin sensitivity to 13 pollen species was detected in patients with respiratory allergy in the region of Thessaloniki. The main pollen involved in respiratory allergy symptoms were selected. The most frequently implicated pollen in SPT sensitization of patients were: 1) grasses, 2) olive, 3) goosefoot and 4) wall pellitory.

All data are presented in our area for the first time and could comprise the infrastructure of many medical, biologic and other scientific fields’ applications.

Ancillary