Generality
Grass allergy is an abnormal and exaggerated reaction of the immune system, induced by the inhalation of pollen grains dispersed in the environment.
The allergy induced by grass pollen is characterized by the appearance of symptoms similar to those of a common cold, such as sneezing, redness and itching of the eyes, abundant nasal discharge and difficulty in breathing.
The onset, intensity and duration of the symptoms depend mainly on the variations in the concentration of pollen present in the atmosphere.
In addition to symptomatic therapy with antihistamine and corticosteroid drugs, there are several preparations for allergenic immunotherapy, with optimal results especially if it started early.
Pollini: what are they?
- Pollens are male reproductive cells (dermatophytes) produced by plants during flowering. These small and light grains have the task of fertilizing other vegetables of the same species.
- Given their small size, anemophilous (airborne) pollens are carried by the air even at great distances and can be easily inhaled, so they are able to penetrate the respiratory tract. The pollen contains special substances, called antigens, capable of "sensitizing" genetically predisposed subjects.
- Allergens are released upon contact with the granule with the moist surface of the respiratory tract. The same pollens have enzymatic activities that facilitate the penetration of allergens through the mucous membranes.
Causes
At the base of grass allergy there is a hypersensitivity reaction of the immune system, mediated by a particular class of antibodies: Immunoglobulins E (IgE). In predisposed subjects, this response is triggered by the inhalation of the allergenic pollen to which it is found to be sensitized (eg. Mazzolina, codolina, grass of the lawn, etc.) during the period of flowering (or pollination).
Note : during the diagnostic phase, IgE can be searched and dosed in the patient's serum to confirm allergic sensitization.
The immune system is activated by mistakenly detecting grass pollens as dangerous substances. The production of IgE stimulates the release of chemical mediators of inflammation: histamine, prostaglandins, leukotrienes, bradykinin and others. These substances act by causing an inflammatory process: they dilate the capillary vessels and attract particular defense cells from the blood and tissues, which participate in the reaction. The end result is the induction of the typical symptomatology of grass allergy.
The presence of allergenic granules is influenced by the climate and the spread of vegetation in the territory. Grasses are herbs characterized by the presence of spikelets of various sizes, which mainly pollinate in spring.
The hottest months for reaching atmospheric pollen concentrations are the hottest: between March and September, with a peak in April and May.
| Pollen calendar | |
| grasses | Pollination period |
| Oats | from May to August |
| Wheat, chaff | from May to June |
| Maize, sorghum | from July to September |
| Rye | from June to July |
| Cannarecchia | from August to September |
| Weedy grass | from June to August |
| Canine grass | from June to October |
| Capellini, agroside | from June to August |
| Caprinella, Small grass | from May to September |
| Tail grass | from May to July |
| Paleo of the meadows | from April to June |
| Paleo, spigolina | from April to June |
| Paleo odorous | from March to July |
| Logliarello | from May to August |
| Gramigna of the streets | from February to November |
| Gramigna of the meadows and barley | from April to August |
Risk factors
Grass allergy is caused by pollen from one of the most widespread vegetable families in the world: there are about 9, 000 different species, including many wild and herbaceous, annual or perennial weeds, which grow spontaneously even in gardens, meadows, uncultivated land and roadsides.
Furthermore, the risk of introducing the same allergens with the diet should not be underestimated: in fact, the cereal-based foods belonging to the grass family are often also present at the table.
| allergen | Main allergenic families | Some examples |
| Grass pollen | Spontaneous grasses | Small grass, tail, paleo odorous, logliarello, grass of the meadows |
| Cultivated grasses (cereals) | Oats, wheat, corn, barley, rye | |
| Grass allergy and foods for which a possible cross-reactivity is described | ||
| Melon, watermelon, orange and citrus fruits, kiwi, tomato, aubergine, peach, apricot, cherry, plum, peanuts, almond, wheat, cereals and their derivatives (bread and pasta). | ||
Symptoms
When the concentration of grass pollen dispersed in the environment reaches a certain threshold, the typical manifestations of allergy may occur in predisposed subjects.
Symptoms vary from person to person and can be mild or severe. The manifestations associated with grass allergy can quickly and abruptly disappear, as they occurred, but sometimes persist for as long as they are exposed to allergens. In some cases, the ailments can already manifest themselves in closed environments (habitation or work place), and then worsen outside; if the allergic person returns indoors, the situation improves, but it takes time before the symptoms disappear.
Grasses mainly cause disturbances in the respiratory system:
- Itchy nose;
- Repeated sneezing attacks;
- Abundant light-colored nasal discharge;
- Congestion of nasal mucous membranes;
- Difficulty breathing (dyspnea);
- Smell reduction.
An attack of grass allergy can cause other signs and symptoms, such as:
- Eye irritation with annoying itching and profuse tearing;
- Itching in the conjunctivae, which appear reddened and edematous;
- Light annoyance (photophobia);
- Itching at the throat, ears and / or palate;
- Sense of general malaise.
Long-term or repeated exposure to grass pollens results in obstruction of the nasal passages and ears after three or four days.
In some people, exposure to grass can trigger the typical symptoms of asthma, such as:
- Shortness of breath (air hunger);
- Sense of chest constriction;
- Wheezing during breathing;
- Dry, angry and persistent cough.
Sometimes, fatigue, irritability, difficulty concentrating, headache, diarrhea, cutaneous manifestations (hives or dermatitis), worsening sleep quality, weakness, states of anxiety and depression appear.
In allergic subjects, in addition to ocular, rhinitic and / or asthmatic symptoms, implications may sometimes occur due to pollen-food cross-reactivity, which occurs with:
- Itching and swelling of the oro-labial mucosa;
- Burning on the palate and throat;
- Swallowing disorders.
These manifestations occur within minutes of ingestion of plant foods, in particular with some types of fresh fruit and vegetables, containing antigens that cause cross-reactions with antigenic pollens: this is the so-called oral allergic syndrome (SOA).
In case of grass allergy, there is also the risk of anaphylactic shock, a rare complication that can cause a cardiovascular collapse and must be treated promptly.
Diagnosis
In the presence of signs and symptoms that suggest grass allergy, it is essential to consult an allergist specialist to confirm the diagnostic hypothesis and rule out other medical problems.
To define the condition, therefore, are indicated:
- History and physical examination : the doctor can reconstruct the patient's medical history, as well as gather information on the symptoms and evaluate the signs present. During the collection of these data, it is necessary to investigate when the disturbances began, their nature, periodicity and any triggers already identified. The elements that can influence the occurrence of a reaction to grasses are the familiarity (ie the existence of allergic relatives), the living conditions and the working activity of the subject in question.
- Prick test (skin test): consists in reproducing to a reduced extent the allergic reaction on the patient's skin. A drop of the suspected allergen is applied to the forearm or back and is penetrated into the dermis thanks to a small puncture in the area. If the person is allergic to the substances tested, a skin reaction occurs (in particular, a red and itchy swelling appears similar to a mosquito bite) within a short time;
- Rast test (specific IgE assay): highlights the reaction of antibodies directed against particular antigens on a blood sample and provides an indication of the patient's sensitivity to exposure to the allergen.
Therapy
The best treatment is to take appropriate measures to avoid exposure to the allergen responsible for the allergic reaction.
For the management of symptoms, the following are mainly prescribed:
- Antihistamines : histamine receptor antagonists that block the release of histamine (produced by the immune system and active during the allergic reaction), alleviating most of the symptoms, in particular itching, sneezing, nasal congestion or watery eyes.
- Corticosteroids : sprayed through spray dispensers or taken orally in the form of tablets, they can reduce the symptoms associated with inflammation of the upper respiratory tract.
- Spray decongestants : they can be used for short periods, to provide rapid relief for nasal congestion.
- Antileukotrienes : drugs for oral use that help to quickly block the action of certain chemicals of the immune system that cause certain symptoms, such as the formation of excess mucus and nasal congestion.
- Desensitizing therapy or specific immunotherapy with allergenic extracts: the results of diagnostic tests can favor the development of a long-lasting desensitization treatment (3-5 years) which allows the "immune" response to allergy to be gradually "trained" reducing the number and intensity of acute episodes.
Prevention
To control the symptomatology of grass allergy, it is important to adopt some preventive behaviors:
- Consult the pollen calendar to know the periods of the year at risk, during which it will be necessary to implement precautionary measures, such as the use of masks.
- During the grass pollination period, avoid going out especially in the morning hours, on sunny, windy days and in dry weather. The pollen grains are mostly present in the atmosphere with a temperature of 25-30 ° C, a relative humidity higher than 60% and a wind with a speed of 5-15 Km / h. For susceptible individuals, it is also risky to go out after a storm: the rain breaks the pollen grains into smaller fragments that easily reach the airways.
- To prevent pollen from entering the home during the flowering season, keep the windows closed during sunny hours, approximately between 10 am and 4 pm. Do not spread the sheets outdoors to prevent them from collecting pollens.
- Avoid parking your car under trees or near gardens and / or lawns. While traveling, instead, preferably keep the windows closed and equip the car with pollen filters, taking care to replace them periodically.
- Shower and wash hair and face more frequently, as pollen grains can remain on the skin or in the hair and be deposited on the pillow from where they are inhaled during sleep or can cause dermatitis.
- Take care of the cleaning of pets: if they go out in the open they can become carriers of grass pollen through the hair.
- Avoid frequenting parks, gardens and lawns, especially if they have just been mown.
- Beware of alcohol: they stimulate the production of mucus and dilate the vessels, threatening to worsen the nasal secretion and congestion associated with grass allergy.
