Route Of Exposure

Allergen Exposure

The genus Taraxacum is a member of the family Asteraceae, subfamily Cichorioideae, tribe Lactuceae. The Asteraceae includes Chrysanthemum, Dandelion, and Mugwort.

The Dandelion is a perennial weed that originated in Europe and Asia and is now naturalised throughout the world. It is particularly abundant in most of the northern hemisphere. In many countries such as Australia, Poland, Italy and Turkey it is considered a weed seriously interfering with agriculture.

Dandelion grows to a height of 0.5 m and a width of 0.3 m. Stems are hollow, very short and wholly underground, producing a rosette of leaves at the ground surface. The leaves are deeply toothed and 5 to 40 cm long.

Dandelion flowers in spring and early summer, sometimes with a secondary flowering in autumn. Flowering occurs for the whole year in warmer climates. The 2-3 cm in diameter flower heads are solitary at the end of naked, hollow stalks. Stalks can reach heights up to 60 cm. One head contains from 100 to 300 yellow ray flowers. The flowers have an unpleasant odour, are hermaphrodite (have both male and female organs) and are pollinated by insects. The plant is apomictic (reproduces by seeds formed without sexual fusion) and self-fertilising.

The seeds are brown and connected to white, feathery structures that are easily carried by the wind or by touch. The seeds ripen from May to June. A parachute of bristles aiding in dissemination tops Dandelion seeds. Seeds travel up to several hundred meters.

The Dandelion is an abundant weed found in lawns, meadows, fields, highways, waste places and the vicinities of railroads. It may also be cultivated.

The small tender leaves can be eaten as salad, the roots can be ground as a substitute for coffee (but are bitter), wine can be fermented from extracts of the flowers, and various parts may be used as medication.

Clinical Relevance

Allergen description

A 18 kDa Bet v 1 related-protein has been isolated from the root of the plant. Whether a similar protein exists in Dandelion pollen was not determined. No allergens from this plant have yet been characterised.

Potential Cross Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a certain degree among members of the family Asteraceae.

Many patients found to be sensitive to Dandelion are likely to have been sensitised by other members of the Asteraceae (Compositae) family, such as the wind-pollinated Mugwort or Ragweed, due to a close botanical relationship. Cross-reactivity has been confirmed between sunflower and other Compositae pollens (Mugwort, Marguerite, Dandelion, Golden rod, and Short ragweed) by RAST and immunoblotting inhibition experiments. Mugwort pollen exhibited the greatest degree of allergenic homology (cross-reactivity) with sunflower pollen, whereas at the other end of the spectrum, Short ragweed showed fewer cross-reactive epitopes.

A study investigated the sensitisation and cross-allergenicity of Chrysanthemum, Dandelion, and Mugwort by reviewing the records of 6,497 respiratory allergic patients who underwent skin prick tests, and concluded that in individuals with respiratory disease, Chrysanthemum and Dandelion were frequently co-sensitised with Mugwort, and that these 2 species also showed extensive cross-allergenicity with Mugwort.

Clinical Experience

IgE-mediated reactions

Anecdotal evidence suggests that asthma, allergic rhinitis and allergic conjunctivitis are common following exposure to pollen from Dandelion; however, few specific studies have been reported to date. A Korean study investigated the sensitisation and cross-allergenicity of Chrysanthemum, Dandelion, and Mugwort by reviewing the records of 6,497 respiratory allergic patients who had been skin prick tested, and found that sensitisation to Mugwort, Chrysanthemum, and Dandelion occurred in 13.4%, 10.0%, and 8.5% of patients, respectively. Co-sensitisation to all three pollens was found in 5.2%. Some patients were monosensitised to 1 species (1.5% to Chrysanthemum, 1.4% to Dandelion, and 4.5% to Mugwort). The study concluded that in individuals with respiratory disease, Chrysanthemum and Dandelion were frequently co-sensitised with Mugwort, and that these 2 species also showed extensive cross-allergenicity with Mugwort. Seasonal allergic contact dermatitis in a florist has been described.

Other reactions

Contact dermatitis due to Dandelion has been described. A 32-year-old atopic patient with allergic rhinitis developed a severe anaphylactic reaction following the ingestion of a pollen compound prepared in an herbalist’s shop. The patient was found to be sensitised to Artemisia vulgaris, Taraxacum officinalis or Salix alba. All three were components of the pollen compound, in the ratio of 15% Taraxacum officinalis, 5% Artemisia vulgaris, and 15% Salix alba. The allergen responsible for the reaction could not be identified with certainty, but the authors caution that a food-induced systemic reaction due to a pollen compound is possible.

Adverse reactions to pollen following ingestion have been documented in other studies. Immediate allergic reactions occurred in 3 patients following the ingestion of a health food known as ”bee pollen”. The bee pollen contained Dandelion pollen. In vivo and in vitro studies demonstrated that the patients were sensitive to several family members, rather than to insect-derived antigens.

Dandelion pollen in honey may also result in allergic reactions. Other pollen, e.g., from other members of the Compositae family, may also result in allergic reactions. However, other possible causes for adverse reactions to honey include bee venom and the presence of bee pharyngeal glands and other bee body components. The authors caution that in individuals allergic to honey, primary sensitisation may be due to the honey itself, to airborne Compositae pollen or even to cross-reacting bee venom components.

Ingestion of other parts of the Dandelion plant has also resulted in adverse reactions, attributed to the presence of sesquiterpene lactonespresent in the leaves and stems.