Summary

Cocksfoot (Dactylis glomerata) is a cool-season grass and one of the most common grasses, portraying its wide use as forage and hay. Cocksfoot very well abides sensitive to extreme conditions of temperature and adapts to the Mediterranean climate. The most common subspecies of cocksfoot accepted includes D. glomerata – ssp. glomerata and ssp. lobata (Drejer) H. Lindb. Cocksfoot belongs to the order: Cyperales; Family: Poaceae; Genus: Dactylis and Species: Dactylis glomerata. The size range of cocksfoot pollen generally varies between 10 microns to 10 nanometers. Pollen exposure of cocksfoot may cause hay fever, asthma, allergic conjunctivitis, or atopic dermatitis. In the US, 75% of the population is exposed to cocksfoot. Allergic rhinitis is a major risk factor for the development of asthma. According to a study conducted in Germany, sensitivity to allergic pollens was observed in 19.7% of patients and the allergic rhinitis diagnosis was present in 8.7% of the population. Out of the allergenic components, Dac g 4, is a major 60 kDa protein. Dac g 4 reports allergenicity, as the majority of plasma samples demonstrated IgE binding to Dac g 4 on IEF-immunoprint. Cocksfoot pollens can be cross-reactive with other pollen allergens such as timothy grass and ryegrass and with wheat. Specific allergen immunotherapy may include administration of the allergen extract, either subcutaneously or sublingually along with other routes

Epidemiology

Worldwide distribution

Cocksfoot is of the most widespread genera to cause grass pollen allergy in the Northern Hemisphere, along with other species. An alarming rise in the seasonal pollen-associated asthma and hay fever has been observed in Australia, wherein, around 10% of adults and 30% of children are identified with respiratory disease.

Within the US, 75% of the population is exposed to cocksfoot. Noticeable exposure patterns are observed based on varied geographic regions, for example, 43% of the population across the southeastern US was exposed to cocksfoot. Moreover, heterogeneous exposure to cocksfoot in the Northwestern US and East Central region was noted with 94% and 98%, respectively.

Risk factors

Globally, aeroallergens play a vital role in causing pollinosis. The airborne pollen aims at the respiratory system directly, which results in hypersensitivity disorders in genetically compromised patients. However, it causes late hypersensitivity in patients with allergic rhinitis, allergic alveolitis, asthma, atopic dermatitis, etc.

The pollens belonging to the Gramineae family are at the top list of causing allergic diseases. According to a study conducted in Germany, a total of 1101 children (aged 8-11 years) showed sensitivity to pollens. Sensitivity was observed in 19.7% of patients and the allergic rhinitis diagnosis was present in 8.7% of the population. Another study performed in adults in Austria, revealed that the most affected age group by the Gramineae family’s pollen allergy was 21-30 years wherein, 17% of healthy individuals were sensitized to grass.

Route Of Exposure

Main

Airway Inhalation

The main route of exposure for cocksfoot pollen is through inhaling which in relay cause hypersensitivity response in cocksfoot pollen-allergic patients. Patients exposed to cocksfoot through inhalation in the airways are likely to suffer from allergic rhinitis, asthma, conjunctivitis, atopic dermatitis, etc.

Clinical Relevance

Allergic rhinitis

Patients with exposed grass pollens exhibit rhinorrhea, nasal obstruction, nasal itching and sneezing. The cytokine levels are reported to increase in nasal secretions in patients with allergic rhinitis after a trigger by an antigen. The elevated levels are reported to play a role in diagnosing the inhalant allergens. According to a study, exposure of cocksfoot resulted in elevated levels of eosinophils, interleukin (IL) 5, IL-6, IL-13, and macrophage inflammatory protein 1β in patients with allergic rhinitis.

Specific chromosome regions are reported to be linked with seasonal allergic rhinitis. A study was conducted, in a genomic search including 48 Japanese families (188 members) with at least 2 siblings with AR due to cocksfoot, the associated chromosomal regions observed were 1p36.2, 4q13.3 y 9q34.3 along with a weak linkage to 5q33.1

Asthma

Allergic rhinitis is a major risk factor for the development of asthma.

Conjunctivitis

Exposure of pollen allergens to the conjunctiva results in itching, injection, and tearing.

Allergic rhinoconjunctivitis is associated with morbidity and further, it also impairs quality of life. Allergen immunotherapy, including extracts of cocksfoot along with other extracts, is efficacious in improving symptom, medication, and combined symptom and medication scores in patients with ongoing treatment pertaining to allergic rhinoconjunctivitis.

Atopic Dermatitis

Exposure to cocksfoot is reported to worsen the existing condition of atopic dermatitis. A first controlled double-blind study was conducted in 34 patients with atopic dermatitis. The exposure of cocksfoot resulted in worsening of the cutaneous symptoms. A flare-up in eczema was observed on the air-exposed skin areas as compared with the covered skin areas. Serum analysis, using the biomarkers such as chemokine C-C motif ligand 17 (CCL17), chemokine C-C motif ligand 22 (CCL22), and interleukin (IL)-4 serum, is used to determine the immune response induced by the exposure of grass pollen. Patients exposed to cocksfoot showed a noticeable elevation of CCL17, CCL22, and IL-4 serum levels.

Prevention And Therapy

Allergen immunotherapy

Specific allergen immunotherapy includes administration of the allergen extract, either subcutaneously or sublingually to decrease the need for other medications. The other options available include via oral, intranasal, epicutaneous, intra-dermal, or intra-lymphatic route.

Prevention strategies

Avoidance

A randomized, double-blind, placebo-controlled, partial-crossover study conducted in 146 patients with seasonal allergic rhinitis exposed to cocksfoot pollens demonstrated a reduction in seasonal allergic rhinitis symptoms with an oral antagonist and thus increasing the effectiveness of the therapy. Controlled exposure of the cocksfoot can help in the reduction of atopic dermatitis associated symptoms.

Cross-Reactivity

According to a study the data reported a high percentage of cross-reactivity between the allergens from cocksfoot, timothy grass and ryegrass that were tested in the population compared to the mixture of grass pollens and to single pollens using the sera of patients. It is also noted to be cross-reactive with wheat pollens.