Allergy to pellitory
Allergy to pellitory is the leading cause of hay fever in the Mediterranean region and one of the most significant in Italy, particularly in the central andand along the coasts southern regions . It differs from other pollen allergies in one unique respect: a pollination season so long that, in many areas, it behaves almost like a perennial hay fever, with symptoms that can persist for much of the year. It is not uncommon to identify cases of monosensitisation to pellitory ( ), which constitutes an allergic profile with significant implications for diagnosis and for the selection of candidates for allergen-specific immunotherapy (AIT).
Ref
D'Amato G. et al. Pollen-related allergy in the Mediterranean area. Allergy, 2007.
Liccardi G, Visone A, Russo M, Saggese M, D'Amato M, D'Amato G. Parietaria pollinosis: clinical and epidemiological aspects. Allergy Asthma Proc. 1996 Jan-Feb;17(1):23-9.
What is parietaria and where does it grow?
Parietaria (genus Parietaria, family Urticaceae) is a perennial weed characteristic of the Mediterranean region. The species of greatest allergological significance are Parietaria judaica – the most widespread in central and southern Italy and on the islands – and Parietaria officinalis, which is more common in the northern regions.
Parietaria grows preferentially in disturbed, nitrogen-rich environments: cracks in walls, rubble, uncultivated land, roadside verges, and peri-urban and rural areas. Its ability to colonise vertical wall surfaces – even in historic city centres – makes it a widespread allergen that is difficult to avoid for those living in urban areas of central and southern Italy.
The plant is widespread throughout Italy, from sea level up to an altitude of around 900 metres, with higher concentrations in the central and southern regions, in Sicily and Sardinia, but also in Liguria and along the coasts, where it is the main cause of pollen-induced respiratory allergies.
Pollen season: an almost year-round pollen allergy
The most characteristic and clinically significant aspect of pellitory allergy is the extraordinary length of the pollination season, which clearly distinguishes it from all other pollen allergies.
- First pollen peak: spring (March–May)
- Second period of high concentration: from mid-summer to early autumn (July–October)
- In regions with a milder climate (southern Italy, Mediterranean coasts): pollen may be detectable almost all year round, with brief interruptions during the coldest winter months
For this reason, in areas where it is most prevalent, pellitory allergy is defined as a perennial or quasi-perennial pollen allergy: patients may experience symptoms for 8–10 months of the year, with a cumulative impact on quality of life comparable to that of allergies to perennial indoor allergens such as house dust mites.
Daily pollen concentrations are strongly influenced by weather conditions: hot, windy and dry days correspond to peaks in exposure; rainfall temporarily reduces concentrations.
Ariano R, Cecchi L, Voltolini S, Quercia O, Scopano E, Ciprandi G; AAIITO Study group on Pollen Allergy Parietaria pollination duration: myth or fact? Eur Ann Allergy Clin Immunol. 2017 Jan;49(1):6-10.
Ariano R, Panzani RC, Chiapella M, Augeri G. Pollinosis in a Mediterranean area (Riviera Ligure, Italy): ten years of pollen counts, correlation with clinical sensitization and meteorological data. J Investig Allergol Clin Immunol. 1994 Mar-Apr;4(2):81-6.
The molecular allergens of pellitory
The main allergens in parietaria pollen are Par j 1 and Par j 2 (and their analogues Par o 1 and Par o 2), —proteins belonging to the LTP (Lipid Transfer Proteins) family, which have been extensively characterised at a molecular level. Both are recognised as clinically relevant sensitisation markers and are responsible for the vast majority of allergic reactions associated with parietaria.
Colombo P, Bonura A, Costa M, Izzo V, Passantino R, Locorotondo G, et al. The allergens of Parietaria. Int Arch Allergy Immunol. 2003;130(3):173-9.
Dorofeeva Y, Colombo P, Blanca M, et al. Expression and characterization of recombinant Par j 1 and Par j 2
resembling the allergenic epitopes of Parietaria Judaica pollen. Sci Rep. 2019;9(1):15043
Monosensitisation: a specific allergic profile
Compared with other pollen allergens, itfor is not uncommon allergy to Parietaria to present as monosensitisation: in such circumstances ,a proportion of patients are sensitised exclusively to Parietaria allergens, without significant co-sensitisation to other pollens.
This profile has important practical implications for both diagnosis and treatment. Patients with monosensitisation to parietaria present a well-defined allergic picture, with a clear correlation between seasonal exposure and the onset of symptoms, which facilitates both diagnosis and the assessment of suitability for allergen-specific immunotherapy.
Monosensitisation is also one of the most desirable profiles for potential allergen-specific immunotherapy (AIT), as expectedthe reduction in symptoms and in the use of symptomatic medication is not hindered by allergy to other inhalants. However, suitability for immunotherapy must be assessed by a specialist allergist.
Ciprandi G, Cirillo I. Monosensitization and polysensitization in allergic rhinitis. Eur J Intern Med. 2011 Dec;22(6):e75-9.
Ciprandi G, Puccinelli P, Incorvaia C, Masieri S. Parietaria Allergy: An Intriguing Challenge for the Allergist. Medicina (Kaunas). 2018 Dec 7;54(6):106.
Symptoms of parietaria allergy
Symptoms, which are particularly acute during peak pollen seasons, can be especially intense and prolonged due to the long duration of the season. In regions with higher exposure, untreated patients may experience an almost continuous burden of symptoms for much of the year.
Nasal symptoms
- Profuse watery nasal discharge
- Intense nasal itching
- Repeated sneezing
- Nasal obstruction
Eye symptoms
- Redness of the eyes
- Itchy and burning eyes
- Excessive tearing
Bronchial symptoms
- Dry cough
- Wheezing
- Dyspnoea (shortness of breath)
- Chest tightness
In Mediterranean regions, a significant proportion of patients sensitised to pellitory-of-the-wall experience bronchial involvement, with asthmatic symptoms documented in a significant percentage of allergic individuals. This finding highlights the importance of early diagnosis and a treatment plan that also includes preventing progression to asthma.
Parietaria and asthma
In patients with bronchial asthma, the long pollination season of parietaria represents a prolonged risk factor for disease stability. Continued exposure to allergens may promote bronchial hyperresponsiveness, contribute to the worsening of respiratory symptoms and influence seasonal clinical variability.
The international consensus documents ARIA and GINA on the management of rhinitis allergicand asthma emphasise the bidirectional link between allergic rhinitis and bronchial asthma (the ‘one airway, one disease’ model): controlling parietaria-induced allergic rhinitis is an integral part of optimal asthma management. In patients with both conditions, the parietaria season requires an integrated treatment plan, agreed with a specialist before the start of the pollen peaks.
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.
Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention, 2025. Updated 15 November 2025. Available from: www.ginasthma.org.
Pollen and food cross-reactivity
In a significant proportion of sensitised individuals, allergy to pellitory may be associated with cross-reactivity with other allergens, including pollen and food allergens.
Cross-reactivity with other pollens
Cross-reactivity with other members of the Urticaceae family, particularly stinging nettle, has been documented. In environments where both plants are present, this can prolong the symptomatic period. Cross-reactivity with allergens from other is also possible families and species, such as trees, weeds or grasses, making it difficult to determine which pollen is responsible for the symptoms if exposures occur during the same period. Parietaria pollen also contains pan-allergens, such as profilins and polcalcins.
Asero R, Mistrello G, Roncarolo D et al. Parietaria profilin shows only limited cross-reactivity with birch and grass profilins. Int Arch Allergy Immunol. 2004; 133: 121-4.
Bonura A, Gulino L, Trapani A, et al. Isolation, expression and immunological characterization of a
calcium-binding protein from Parietaria pollen. Mol Immunol. 2008;45(9):2465-2473.
Cross-reactivity with foods
The literature reports cross-reactions with certain plant-based foods, including basil, mulberries, melon, figs, peas, pistachios and cherries. Symptoms typically present as oral allergy syndrome (OAS): itching and discomfort localised in the mouth, which appear within a few minutes of ingesting the raw food and resolve spontaneously.
The LTP nature of the main allergens in pellitory (Par j 1, Par j 2) implies that, in some individuals, food cross-reactions may potentially be more widespread than oral reactions alone, although systemic reactions remain rare. It is known, in fact, that LTP from pellitory not iscross-reactive with other LTPs, such as those from peaches and hazelnuts; consequently it is not considered a marker of LTP-induced food syndrome,. Its clinical significance must be assessed on a case-by-case basis by a specialist.
The presence of cross-reactivity does not necessarily imply the onset of clinical symptoms in all sensitised individuals. Any food reactions must always be reported to an allergist for an individualised assessment.
Tordesillas L, Sirvent S, Díaz-Perales A, et al. Plant lipid transfer protein allergens: no cross-reactivity
between those from foods and olive and Parietaria pollen. Int Arch Allergy Immunol. 2011;156(3):291-296.
Liccardi G, Russo M, Mistrello G, Falagiani P, D'Amato M, D'Amato G. Sensitization to pistachio is common in Parietaria allergy. Allergy. 1999 Jun;54(6):643-5
Impact on quality of life
Parietaria is among the pollen allergies with the greatest cumulative impact on quality of life, due to the combination of high allergenicity and the exceptionally long exposure season. In areas of highest prevalence, patients who are not adequately treated may experience symptoms for much of the year.
The most significant consequences include:
- Persistent and long-lasting respiratory and ocular symptoms
- Sleep disturbances due to night-time and morning symptoms
- Reduced ability to concentrate and impaired work or academic performance over prolonged periods
- Restrictions on outdoor activities during the long pollen season
- l worsening of asthma and an increased risk of exacerbations
- Psychological impact linked to the perception of a quasi-perennial allergic condition
Active management of pellitory allergy – which includes appropriate drug therapy and, where indicated, allergen-specific immunotherapy – is particularly important in this form of hay fever due to the extent and duration of the impact clinical.
Reducing exposure: practical measures
Reducing exposure to pellitory pollen is made difficult by the plant’s widespread presence across the region. Unlike grasses – which are concentrated in meadows and open areas – pellitory grows directly on walls and in the cracks of buildings, making avoidance particularly challenging.
- Monitor regional pollen forecasts and limit outdoor activities on days when concentrations are high
- Avoid going out during the middle of the day on hot, windy days, when pollen concentrations are at their highest
- Keep windows closed during pollen peaks and use air conditioning with suitable filters
- Take a shower and change your clothes after being outdoors
- Wear wraparound sunglasses to reduce contact between pollen and the mucous membranes of the eyes
- Where possible, remove pellitory plants in the immediate vicinity of your home before they flower
These exposure-reduction measures are provided for information purposes and should be regarded as complementary to drug therapy and any immunotherapy, as part of a treatment plan agreed with your doctor.
Frequently asked questions
Parietaria is a perennial plant capable of producing pollen almost continuously from spring to late autumn. Unlike grasses — which have a flowering season concentrated into a few weeks — or birch — which flowers early but for a short period — parietaria maintains active pollen production for months. In Mediterranean regions with mild winters, there may be very few breaks in pollen release, making pellitory the only true pollen allergy with an almost year-round pattern.
Yes, although it is less prevalent than in the central and southern regions. Parietaria officinalis is found in the northern regions, particularly along the coasts and in urban and pre-Alpine areas. The pollen season is slightly shorter than in the south, but sensitisation to pellitory is nevertheless documented and clinically significant even in patients in northern Italy.
A patient with monosensitisation to pellitory is sensitised exclusively to this allergen, without cross-sensitisation to other pollens (grasses, birch, olive, etc.). This profile, which is not uncommon compared to other pollens, simplifies diagnosis and highlights the clinical correlation that is a key factor in selecting patients whoforare candidates allergen-specific immunotherapy.
Yes. The long duration of the pollen season and prolonged exposure to allergens contribute to the progression of the allergic condition, with a possible progression from allergic rhinitis to bronchial asthma (‘allergic march’). For this reason, early diagnosis and an active treatment plan – including an assessment of whether allergen-specific immunotherapy is indicated – are particularly important in cases of pellitory allergy.
Yes. Allergen-specific immunotherapy (AIT) using Parietaria extracts is a treatment capable of modifying the patient’s immune response, reducing sensitisation and the long-term progression of the disease. Suitability for this treatment must be assessed by an allergy specialist based on the patient’s clinical and molecular profile.
You should see a doctor if you experience nasal, ocular or bronchial symptoms that occur regularly in spring or summer–autumn, last for weeks or months, or do not respond adequately to symptomatic medication. An allergy assessment involving skin prick tests and, where indicated, molecular diagnostics, allows the diagnosis to be confirmed and the most appropriate treatment plan to be established.
Practical insights
Information notice
The information contained 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 choice and management of drug therapies and allergen-specific immunotherapy, you should consult your specialist doctor. The practical guidelines provided are intended as complementary measures to support exposure management, as part of an individualised treatment plan.