Summary

The long-lived perennial common reed (Phragmites australis, previously known as P. communis) is one of the most widely distributed flowering plants and can be found in stationary or slow-moving aquatic habitats throughout the world. Flowering occurs in late summer in Europe, and the pollen can induce respiratory and cutaneous symptoms in sensitized individuals, however few studies have been reported to date. Variable degrees of cross-reactivity have been reported between the common reed and grasses of other subfamilies within the Poaceae.

Route Of Exposure

Main

Pollen from common reed is an aeroallergen that can elicit respiratory and cutaneous symptoms in sensitized individuals.

Clinical Relevance

IgE-mediated reactions

Anecdotal evidence suggests that pollen from common reed can induce asthma, allergic rhinitis, allergic conjunctivitis and cutaneous symptoms in sensitised individuals; however, few studies have been reported to date.

A study in Spain reported that 90% (27/30) of patients with respiratory symptoms during grass pollen season were sensitized to common reed (cited by the authors as P. communis). Of the 31 patients initially recruited into this study (one patient was excluded), all had rhinitis, 20 had conjunctivitis, 6 had asthma and 6 had cutaneous symptoms.

Cross-Reactivity

A certain degree of cross-reactivity among members of the Poaecea family may be expected as most species of grass pollen contain at least the Group 1, Group 5 and Group 13 grass allergens. However, the extent of cross-reactivity between common reed and other grass species may depend on their taxonomic relationship, with significantly higher average inhibition of IgE binding likely for pollen extracts of grasses within the same group, and lower levels of inhibition seen for grasses that are more distantly related. For example, Duffort et al. (2008) demonstrated that antigentic similarity among Group 1 allergens is very high among grasses in the Pooideae subfamily, but lower among grasses from other subfamilies such as Arundinoideae (common reed, P. communis) and Chloridoideae (Bermuda grass, C. dactylon).

Timothy grass pollen Phl p2 cross-reacted weakly with Group 2 allergens from cultivated oat and common reed pollens.

Pollen from 17 grass species including common reed (cited by the authors as P. communis) was used to test IgE reactivity of sera from 800 individuals suspected of an inhalant allergy in North America and Europe. Within this cohort, specific IgE antibodies against one or more grass species were detected in about a quarter (26.1%, 209/800) of sera, however IgE responses to P. communis were lower - by a factor of approximately 5 - than those to species in the Pooideae subfamily such as Kentucky bluegrass (Poa pratensis), creeping fescue (Festuca rubra), timothy grass (Phleum pratense), orchard grass (Dactylis glomerata) and ryegrass (Lolium perenne).

A study in Spain reported that 90% (27/30) of patients with respiratory symptoms such as rhinitis and/or asthma during grass pollen season and specific IgE to a grass mixture extracted from grasses from the Pooideae subfamily were also sensitized to common reed (cited by the authors as P. communis), and 80% (24/30) were sensitized to Bermuda grass (Cynodon dactylon). Of the 31 patients initially recruited into this study (one patient was excluded), all had rhinitis, 20 had conjunctivitis, 6 had asthma and 6 had cutaneous symptoms.