Ragweed dermatitis and the distribution of ragweed in Australia

Distinctive foliar features and volatile profiles in three Ambrosia species (Asteraceae)

Ambrosia species differ both in their trichome types and in metabolic profiles of leaf volatiles. The current study provides tools for easier taxonomic identification of ragweed species. The genus Ambrosia (Asteraceae) includes some of the most noxious allergenic invasive weeds in the world. Due to high polymorphism in this genus, identification of species is often difficult. This study focuses on microscopic investigation of foliar features and GC-MS identification of the main leaf volatile components of three Ambrosia species currently found in Israel-invasive species Ambrosia confertiflora and A. tenuifolia, and transient A. grayi. A. confertiflora and A. tenuifolia have three trichome types: non-glandular trichomes, capitate glandular trichomes and linear glandular trichomes. Their non-glandular trichomes and capitate trichomes have distinct structures and can serve as taxonomic characters. A. grayi (the least successful invader) has only very dense covering trichomes. All three Ambrosia species have secretory structures in their leaf midrib. A. confertiflora, the most problematic invasive plant in Israel, had a ten times higher volatiles content than the other two species. In A. confertiflora, the most abundant volatiles were chrysanthenone (25.5%), borneol (18%), germacrene D and (E)-caryophyllene (both around 12%). In A. tenuifolia, the most abundant volatiles were β-myrcene (32.9%), (2E)-hexenal (13%) and 1,8-cineole (11.7%). In A. grayi, the most abundant volatiles were β-myrcene (17.9%), germacrene D (17.8%) and limonene (14%). The three examined species have distinct trichome types and metabolic profiles. Non-glandular trichomes show structural diversification between species and are a good descriptive character. Considering the anthropocentric significance of this highly problematic genus, the current study provides tools for easier identification of ragweed species.

Evolution of clinical pattern of parthenium dermatitis: a study of 74 cases

Our aim was to study the evolution of clinical pattern of parthenium dermatitis. Patients with clinical picture consistent with parthenium dermatitis for 3 years or more along with positive patch test to parthenium were studied. Patients were questioned regarding the site(s) of dermatitis at the onset and change in localization in the following years. Patients were classified into airborne contact dermatitis, chronic actinic dermatitis (CAD) pattern or mixed pattern dermatitis. There were 74 patients (49 men and 25 women) with an age range of 22-70 years and the mean duration of 7.7 years. 60 (39 men and 21 women) patients had airborne contact dermatitis, 5 mixed pattern and 9 CAD pattern at the onset. Of the 60 patients with airborne contact dermatitis, 27 (19 men and 8 women) changed to CAD pattern and 11 (6 men and 5 women) to mixed pattern after an average period of 4.2 years. Of the 19 patients photopatch-tested with parthenium, 3 showed photoallergic reaction and the other 3 showed photoaggravation. Our results suggest that the clinical pattern of parthenium dermatitis undergoes a significant change after the onset, i.e. progresses from airborne contact dermatitis to mixed pattern or CAD pattern.

Late summer and fall (March-May) pollen allergy and respiratory disease in Northern New South Wales, Australia

BACKGROUND

Many people in the subtropical Northern Rivers area of New South Wales, Australia, blame the pollen of Tibouchina tree, which flowers at the same time as ragweed, Bahia grass and Bermuda grass, for hayfever and asthma exacerbations during fall between March and May.

OBJECTIVES

To determine whether Tibouchina pollen is allergenic. To determine whether airborne ragweed pollen is present in this region for sufficient length of time and concentration to cause fall respiratory symptoms, and to determine if Bahia grass and Bermuda grass are associated with fall respiratory symptoms.

METHODS

Pollen and Alternaria spores were monitored using a Burkard 7-day spore trap. Two hundred and six volunteers in the Northern Rivers area filled in questionnaires before skin prick tests (SPT) were performed with a panel of skin testing extracts.

RESULTS

One hundred fifty-three (74.3%) subjects were atopic and reacted to one or more aeroallergens. Seventy were SPT positive to ragweed, OR 3.36 (CI 1.03 to 12.15) and 11 to Tibouchina (OR incalculable). Fifty of the 70 ragweed-positive subjects had fall hayfever or exacerbations of hayfever and/or asthma, OR 23.4 (CI 8.90 to 64.00). Eleven subjects were SPT positive to Tibouchina extract. There was a statistical association between Bermuda grass and hayfever, but not asthma OR 13.44 (CI 1.85 to 27.04).

CONCLUSIONS

Ragweed pollen was present for a sufficient length of time and concentration to sensitize and provoke fall hayfever and asthma exacerbations. Tibouchina pollen is an aeroallergen causing mild-to-moderate allergic symptoms in a few people. There is an association between Bahia grass and asthma in children, and between Bermuda grass and allergic rhinitis in adults.

Aero-allergens in canine atopic dermatitis in southeastern Australia based on 1000 intradermal skin tests

OBJECTIVE

To determine the most relevant aero-allergens involved in canine atopic dermatitis in southeastern Australia and provide information about these aero-allergens to the general practitioner.

PROCEDURE

Dogs presented to the Animal Skin & Allergy Clinic with history and clinical signs of atopic dermatitis were injected intradermally with 38 different allergens and negative and positive control. Intradermal skin tests in 1000 dogs were retrospectively evaluated.

RESULTS

One third of all patients reacted to the house dust mite Dermatophagoides farinae. Allergens reacting in more than 15% of the patients were wheat (Triticum aestivum), sweet vernal (Anthoxanthum odoratum), English couch (Agropyron repens), yellow dock (Rumex crispus), Mexican tea (Chenopodium ambrosioides), plantain (Plantago lanceolata), melaleuca (Melaleuca quinquenervia) and peppercorn (Schimus spp).

CONCLUSION

House dust mites are the most common allergens in canine atopic dermatitis in southeastern Australia and D farinae is involved most frequently. However, a number of grass, weed and tree pollens also are involved regularly.

Compositae dermatitis

Compositae dermatitis is an allergic contact dermatitis. The most important allergens in the Compositae family are sesquiterpene lactones (SL), which are present in the oleoresin fraction of leaf, stem, flower and possibly pollen. Compositae dermatitis is most frequently seen in middle-aged and elderly people in patterns reflecting airborne or direct contact with the allergens. The pattern typically starts in summer and disappears in the autumn or winter. Repeated exposure over many years may lead to a chronic and, at times, a disseminated pattern. Seasonal variation does not occur in occupational Compositae dermatitis. In addition to the classically described airborne pattern of face, 'V' of neck, hands and forearms, hand dermatitis is now recognized to be an equally common presentation. This variability of clinical features, and the frequent occurrence of atopic dermatitis and contact allergy to one or more compounds, highlights the need for routine patch testing with sesquiterpene lactone mix 0.1% (Thermal, Hamburg, Germany), combined with aimed patch testing with Compositae plants and extracts. Avoidance of the plants and plant extracts of this large family can be difficult due to its widespread occurrence in flower, herb and vegetable gardens, urban and rural weed population and native vegetation. Importantly, Compositae plant extracts are present in many cosmetics, shampoos, herbal creams and ingested herbal remedies and tonics.