Grass allergy
Grass allergy is the most common form of hay fever in Italy and Europe. It affects a significant proportion of the adult and paediatric population, with a significant impact on quality of life during the spring and summer months. It is a chronic but manageable condition, for which effective treatment strategies exist, including allergen-specific immunotherapy, which may be able to alter the natural course of the disease.
Ref
D'Amato G. et al. Allergenic pollen and pollen allergy in Europe. Allergy, 2007.
Bousquet P-J, Chinn S, Janson C, Kogevinas M, Burney P, Jarvis D. Geographical variation in the prevalence of positive skin tests to environmental aeroallergens in the European Community Respiratory Health Survey I. Allergy 2007;62:301–309.
What is grass pollen allergy?
Grass allergy is an IgE-mediated respiratory allergic condition caused by the inhalation of pollen produced by plants belonging to the Poaceae (or Graminaceae) family, one of the most widespread botanical families in the world.
Grasses are found in urban, rural and natural environments and represent one of the main causes of respiratory allergic sensitisation due to their wide geographical distribution and high pollen production.
Among the most clinically relevant and common species, Phleum pratense (timothy grass) is considered the reference allergen for the diagnosis and treatment of sensitisation to grass pollens of the Pooideae subfamily.
García-Mozo H. Poaceae pollen as the leading aeroallergen worldwide: A review. Allergy. 2017 Dec;72(12):1849-1858
Grass allergens
Grass allergens are proteins and, for classification purposes, are normally organised into molecular groups of varying clinical significance. The most important are:
- Group 1 (e.g. Phl p 1), specific to the Poaceae family, and present in over 90% of individuals sensitised to grasses
- Group 5 (e.g. Phl p 5), specific to the Pooideae subfamily, affects 65–90% of patients sensitised to grasses
Group 1 and Group 5 are considered markers of primary sensitisation to grass pollen and, in some rare cases where IgE specific to the first group is absent, the second group provides reliable evidence of actual sensitisation.
These allergens are involved in the vast majority of allergic reactions to grass pollen and are also relevant for molecular diagnosis and the selection of patients suitable for immunotherapy.
There are also pan-allergens (such as Phl p7 and Phl p12), which underlie cross-reactivity with pollens from other families and various foods.
The allergenic particles associated with pollen are small in size, a characteristic that facilitates their penetration into the lower airways, with possible bronchial involvement in susceptible individuals.
Bokanovic D, Aberer W, Hemmer W, Heinemann A, Komericki P, Scheffel J et al. Determination of sIgE to rPhl p 1 is sufficient to diagnose grass pollen allergy. Allergy Eur J Allergy Clin Immunol 2013;68:1403–1409.
Popescu F-D. Molecular biomarkers for grass pollen immunotherapy. World J Methodol 2014;4:26.
Darsow U, Brockow K, Pfab F, Jakob T, Petersson CJ, Borres MP et al. Allergens. Heterogeneity of
molecular sensitization profiles in grass pollen allergy - implications for immunotherapy? Clin Exp
Allergy 2014;44:778-786.
Roberts G. et al. EAACI Guidelines on Allergen Immunotherapy. Allergy, 2018.
Arshad SH. Does allergen immunotherapy for allergic rhinitis prevent asthma? Ann Allergy Asthma Immunol. 2022 Sep;129(3):286-291
When symptoms appear: the pollen calendar
Grass allergy is a seasonal allergy: symptoms appear during the pollination season, which in Italy follows a predictable pattern, with possible variations depending on the climate and geographical location.
- Start of flowering: generally between late March and April
- Pollen peaks: mainly in May
- End of the season: pollen may remain present until August–September
Fluctuations in pollen concentration — linked to weather variables such as temperature, wind and rainfall — can lead to significant variability in the severity of symptoms from one day to the next and throughout the season.
How the allergic reaction develops
In genetically predisposed individuals, the first exposure to grass pollen, which acts as an allergen, triggers the production of specific antibodies (IgE) by the immune system (a process known as sensitisation). Upon subsequent exposure, the IgE antibodies bound to the surface of mast cells recognise the allergen and trigger the release of inflammatory chemical mediators — primarily histamine — which cause the symptoms to appear.
Due to their physical characteristics, grass allergens can settle on both the nasal and ocular mucous membranes and reach the lower airways. In susceptible individuals, intense or prolonged exposure may be associated with the onset or worsening of asthmatic symptoms.
This mechanism underpins the ‘one airway, one disease’ model, which describes the frequent co-existence of allergic rhinitis and bronchial asthma as manifestations of the same inflammatory process affecting the entire respiratory tract.
Bousquet J, et al; Aria Workshop Group; World Health organization. Allergic rhinitis and its effect on asthma.
J Allergy Clin Immunol 2001; 108: S147–S334.
Symptoms of grass pollen allergy
Symptoms appear or worsen during the pollen season and may affect the upper airways, the eyes and, in susceptible individuals, the lower airways.
Nasal symptoms
- Repeated sneezing
- Itchy nose
- Profuse watery nasal discharge
- Nasal congestion
Eye symptoms
- Redness of the eyes
- Itchy and burning eyes
- Excessive tearing
Bronchial symptoms
- Dry cough
- Wheezing
- Dyspnoea (shortness of breath)
- Tightness in the chest
Oral allergy syndrome (OAS)
In some sensitised individuals, grass allergy may be associated with oral allergy syndrome, characterised by itching and discomfort localised in the mouth following the ingestion of specific raw plant-based foods. This is a manifestation of allergenic cross-reactivity caused by pan-allergens, and is generally mild and self-limiting.
Ref.
[Asero R. et al. Oral allergy syndrome: an update for the clinician. Eur Ann Allergy Clin Immunol, 2013.
Popescu FD. Cross-reactivity between aeroallergens and food allergens. World J Methodol. 2015;5(2):31-50.]
Pollen and food cross-reactivity
Grasses may exhibit cross-reactivity with other allergens, both pollen and food-based. This means that certain allergenic proteins in grasses share similar structures with those found in other pollens or foods, which can trigger cross-reactions in individuals who are already sensitised. Cross-reactivity is also present between different members of the Poaceae family.
Cross-reactivity with other pollens
- Olive pollen
- Birch pollen
Cross-reactivity with plant-based foods
Cross-reactions have been documented with certain foods belonging to the Rosaceae family (apple, peach, pear), the Cucurbitaceae family (melon, watermelon), the Actinidiaceae family (kiwi), Apiaceae (carrots, celery), Rutaceae (citrus fruits), Leguminosae (peanuts, soya), Solanaceae (tomatoes), Bromeliaceae (pineapple), Corylaceae (hazelnuts), Asteraceae (sunflowers) and Moraceae (figs).
Symptoms are generally limited to the mouth (oral allergy syndrome). However, consuming large quantities may lead to gastrointestinal or systemic symptoms.
It is important to emphasise that the presence of cross-reactivity does not necessarily imply the onset of clinical symptoms: the clinical significance of any reactions must be assessed on a case-by-case basis by a specialist doctor.
Hauser M, Roulias A, Ferreira F, Egger M. Panallergens and their impact on the allergic patient. Allergy Asthma Clin Immunol 2010;6:1.
Cases B, Ibañez MD, Tudela JI, Sanchez-Garcia S, Del Rio PR, Fernandez EA, Escudero C, Fernandez-Caldas E. Immunological cross-reactivity between olive and grass pollen: implication of major and minor allergens. Immunological cross-reactivity between olive and grass pollen: implication of major and minor allergens.
Asero R, Mistrello G, Roncarolo D, Amato S, Zanoni D, Barocci F, et al. Detection of clinical markers of sensitization to profilin in patients allergic to plantderived foods. J Allergy Clin Immunol 2003; 112: 427-32Barber D, de la Torre F, Lombardero M, Antépara I, Colas C, Dávila I, Tabar AI, Vidal C, Villalba M, Salcedo G, Rodríguez R. Component-resolved diagnosis of pollen allergy based on skin testing with profilin, polcalcin and lipid transfer protein pan-allergens. Clin Exp Allergy 2009;39:1764-1773
Impact on quality of life
Grass allergy can have a significant impact on quality of life during the pollen season. The variability and severity of symptoms can interfere with:
- Sleep quality and night-time rest
- The ability to concentrate and performance at work or school
- Participation in outdoor and sporting activities
- Asthma control in patients with bronchial comorbidities
According to the ARIA guidelines for the management of allergic rhinitis, seasonal respiratory allergies represent a condition with a measurable impact on patients’ well-being and functional capacity, and warrant active, personalised management.
Laurent Laforest , Jean Bousquet, Guilhem Pietri, Vasilisa Sazonov Kocevar, Donald Yin, Yves Pacheco, Eric Van Ganse. Quality of life during pollen season in patients with seasonal allergic rhinitis with or without asthma. Int Arch Allergy Immunol. 2005 Mar;136(3):281-6
Bousquet J, et al; Aria Workshop Group; World Health organization. Allergic rhinitis and its effect on asthma.
J Allergy Clin Immunol 2001; 108: S147–S334.
Frequently asked questions
So-called ‘hay fever’ is a colloquial term describing seasonal allergic rhinitis caused by pollen, including that from grasses. It does not involve a fever in the strict sense: the name derives from the sensation of heat and malaise that the symptoms can cause during the flowering season.
A grass allergy can be distinguished from the common cold by the absence of a fever, by the fact that it occurs during the pollen season, by the frequent presence of intense itching of the eyes and nose, and by the prolonged duration of the symptoms. If in doubt, it is advisable to consult a doctor for an allergy assessment.
A grass allergy can develop at any age and is more common in people with a family history of atopic conditions (such as asthma, allergic rhinitis or atopic dermatitis). Initial sensitisation often occurs during childhood or adolescence.
Yes. Without appropriate treatment, allergic rhinitis caused by grasses can progress to involve the lower airways (bronchial asthma), a phenomenon known as the ‘allergic march’. For this reason, early diagnosis and active management of the condition are essential.
Yes. Allergen-specific immunotherapy (ASIT) — available in subcutaneous (SCIT) or sublingual (SLIT) form — is a treatment that has the potential to modify the patient’s immune response to grass allergens, reducing sensitisation and the long-term progression of the condition. Suitability for immunotherapy must be assessed by a specialist doctor.
You should see your doctor if you experience nasal, eye or bronchial symptoms that occur regularly in spring or summer, which limit your daily activities or do not respond adequately to symptomatic medication. An allergy assessment will confirm the diagnosis, identify the allergens responsible and help establish the most appropriate treatment plan.
Practical insights
Information notice
The information on this page is for educational purposes only and is not a substitute for the advice of a doctor or other qualified healthcare professionals. For a clinical assessment and any treatment decisions, including the selection and management of drug therapies and allergen-specific immunotherapy, you should consult your specialist. The practical guidelines provided are intended as complementary measures to support exposure management, as part of an individualised treatment plan.