What is Parietaria judaica? – Botanical characteristics and distribution
Jewish parietaria It is a perennial herbaceous plant belonging to the family Urticaceae., the same family as the nettle, although unlike the latter, the hairs of the parietaria are not stinging. It is also widely known by common names such as wall grass, snail grass, basil, hair grass, ruin grass or paleograss, depending on the region and language. Its scientific names include variants such as Parietaria diffusa, Parietaria officinalis subsp. judaica, and other botanical synonyms.
This plant stands out for its reddish or pinkish stems covered with fine hairs and green leaves with a rhomboidal shape and smooth edges. flowers They are small, white or pink, and cluster close to the stem. At the end of flowering, they produce fruits in the form of small, dark-colored achenes.
La Jewish parietaria It is native to the Mediterranean region, although its distribution currently includes Central and Southeastern Europe, in addition to being present in Great Britain, the Canary Islands, Australia and non-tropical areas of America, especially in humid regions. It is a true urban and rural weeds frequently found in walls, rocks, fissures, cliffs, vacant lots, old houses and uncultivated areasIt is also recognized for its ability to grow in nitrogen-rich areas.
Similar species and names in different regions
Within the genus Parietaria there are several species similar to judaica, highlighting parietaria officinalis, Parietaria mauritanica y Parietaria lusitanica. They all belong to the Urticaceae family, along with nettles (Urtica urens, Urtica pilulifera, Urtica dioica). Commonly, the Jewish parietaria It receives multiple names depending on the language or region:
- Catalan: rocamorella, herba de paret, herba de mur, herba de cargol, granadella, morella
- Spanish: Parietaria, wall herb, snail herb, basil, hairy herb, river basil, wild basil
- Basque: orma-belarr, odar, zigu, muru-belarr, andredena
- Galician: pulitaria
Life cycle and flowering
It is a plant perennial that can reach between 30 and 100 cm highIts flowering is prolonged and variable, covering most of the year depending on the geographical location and climatic conditions. In many regions, the Jewish parietaria It can bloom from late winter to autumn, which means a constant pollen release throughout most of the year. In Mediterranean areas, flowering usually extends from March to October, with peaks in spring and sometimes a rebound in autumn.
The plant has a curious mechanism of pollen propulsion which allows it to disperse even without the aid of wind, which contributes to the persistence of the allergen in the atmosphere. Parietaria pollen is very small (13-19 microns) and can remain suspended for long periods, making exposure easier for people with allergies.
Allergenic importance of Parietaria judaica
Pollen of the Jewish parietaria is one of most potent allergens in Mediterranean coastal regions, being the main cause of allergies in these areas, unlike inland areas where its impact is less severe. The plant can cause allergy symptoms almost year-round, although symptoms are especially intense in spring and, to a lesser extent, in autumn.
El major allergen of the Parietaria judaica is a glycoprotein called Par j, present in the majority (up to 95%) of sensitized patients. It is important to note that there is no cross-reactivity significant with other urticaceae such as nettle, despite its botanical closeness and macroscopic similarity; this means that people allergic to parietaria do not usually experience symptoms upon contact with nettle.
The extraordinary persistence of pollen in the atmosphere, combined with the location of the plant in urban environments, makes allergy to Parietaria judaica common and causes symptoms. multi-seasonal or, in some cases, almost perennial.
Symptoms of Parietaria judaica pollen allergy
La Parietaria pollen allergy It can affect both children and adults, although a higher start frequency of symptoms between the ages of 15 and 30, with a slight predominance in women over men. Symptoms can vary in intensity and are usually more pronounced in people who live in coastal cities and areas with a high presence of the plant.
- El most frequent symptom is allergic rhinoconjunctivitis (up to 80% of those affected), manifested by nasal congestion, sneezing, nasal and eye itching, watery mucus, tearing and redness of the eyes
- El bronchial asthma and spasmodic cough They are also common (up to 48% have asthma), being more intense in monosensitized people, although it is usually associated with rhinoconjunctivitis.
- Some people experience skin symptoms such as itching and redness of the skin, although they are less common
- It is characteristic the velopalatine itching (itching in the soft palate area)
- In severe cases it can trigger asthmatic crisis with a feeling of chest tightness and difficulty breathing
Because pollen is extremely light and persistent, discomfort can last longer than with other seasonal allergies. Furthermore, contact with pollen can be direct (outdoors) or indirect (through unwashed food, clothing, or pet hair).
Frequency of sensitization and polysensitization
La sensitization to Parietaria pollen It is not always isolated. Many patients present sensitization to several types of pollen (polysensitization). In these cases, the allergy to Parietaria is usually associated especially with grasses (about 85% of cases), Olea europaea (around 41%), and house dust mites (dermatophagoides farinae and pteronyssinus, with 37% and 36% respectively).
The persistence and overlap between the cycles of different pollens can make it difficult to identify the allergen responsible for the symptoms without a specific study performed by an allergist.
Differences between Parietaria and Urtica
Although the nettle (Urtica) belongs to the same family, the pollen of both plants does not present cross reactivity significant, meaning that a person can be allergic to Parietaria but not to nettle, and vice versa. Both types of pollen may look similar under a microscope, but their antigenic components differ enough not to provoke cross-immune responses in most cases.
Diagnosis of allergy to Parietaria judaica
El diagnosis Allergy screening is performed by skin prick tests or, if necessary, specific blood IgE tests against the main components of Parietaria pollen (especially the glycoprotein Par j). For an accurate diagnosis, it is advisable to consult a allergist, who will be able to assess the need to confirm sensitivity through controlled exposure testing, especially if there is polysensitization or persistent symptoms outside the expected time period.
Treatment of Parietaria judaica allergy
The treatment is based on several strategies, combining the allergen avoidance, the use of symptomatic medications and, in selected cases, immunotherapy specific:
- Avoid exposure to pollen It is essential, although it can be complicated due to the wide dispersion and duration of pollination. It is recommended to stay indoors during times of high concentration, especially during dawn, dusk, and on windy days.
- antihistamine drugs: useful for controlling nasal, ocular and skin symptoms
- Topical nasal corticosteroids and bronchodilators: in cases of intense rhinoconjunctivitis or bronchial asthma
- Specific immunotherapy (vaccines): is the only treatment that can modify the natural progression of allergic disease. It consists of administering increasing doses of the allergen under medical supervision to induce tolerance.
Immunotherapy is recommended for patients with severe, prolonged, or treatment-resistant symptoms and should be personalized after an appropriate sensitization study.
Preventive measures for those allergic to Parietaria judaica
- Keep the windows closed from home and car, especially during periods of high pollination
- wear sunglasses when going outside to reduce pollen contact with the eyes
- Wash fresh vegetables before consuming them, as they may have pollen on their surface
- Shower and change clothes when you get home, especially after having been outside
- Do not hang clothes outside during the pollination season to prevent pollen from sticking to clothing
- Avoid walks and outdoor activities During dawn and dusk, and especially on dry, sunny and windy days, which is when the pollen concentration is highest.
- Install pollen filters in air conditioning systems and in the car
- Check pollen levels in your geographic area to take additional precautions
- Avoid exposure to other irritants such as smoke, tobacco, hairspray, insecticides, perfumes, pollution and intense physical exertion during pollination, as they can aggravate the symptoms
- In all cases, tobacco is totally discouraged
Additional curiosities and considerations about Parietaria judaica
In some areas, Parietaria judaica is nicknamed asthma weed due to the high frequency of respiratory symptoms in sensitized individuals. It is also an important habitat for certain butterfly species, and its presence on urban walls and crevices makes it a particularly bothersome plant for people with allergies.
The amount of pollen suspended in the air can vary considerably from year to year, depending on environmental factors such as temperature, rainfall, CO2 concentration, and ultraviolet radiation. This means that in some years the symptoms can be much more intense, with pollen counts much higher than average.
The study and cloning of the major allergens in Parietaria has improved allergy diagnosis and treatment, offering greater safety and efficacy in specific immunotherapy. Furthermore, recent developments in diagnostic reagents (DVIs) allow for faster and more accurate identification of sensitization.
Despite the discomfort that it may cause, Jewish parietaria For those who suffer from pollen allergies, it's important to remember that proper identification, medical follow-up, and preventive measures can significantly improve quality of life. If the discomfort persists, consultation with an allergist is essential to establish the most appropriate diagnosis and treatment.