Substance Info: (and synonyms)|
Common names: White Mulberry, Russian Mulberry, Silkworm Mulberry
M. nigra L. - Black Mulberry tree
M. rubra L. - Red Mulberry tree
M. multicaulis Loud
Broussonetia papyrifera - Paper Mulberry
Mulberry tree pollen is a highly allergenic and is an important allergen in urbanised and rural communities where this tree is planted. In these places the prevalence of atopic sensitisation to pollen from this tree is expected to be high.
The Mulberry tree origins are China, Japan, Thailand and Malaysia. The tree is now found throughout the world, including eastern and midwestern USA.
The Mulberry tree is a deciduous tree growing to 18 m - 20 m by 10m, with a wide-spreading, round-top. The trunk is light grey. The green leaves are alternate, simple and toothed, and usually smooth above, glabrous or pubescent along veins beneath. They may be un-lobed, mitten- shaped, or 3-lobed.
The tree flowers in spring, producing small, greenish-yellow flowers, in dense spikes up to 2 cm long. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant). The plant is self-fertile. It is wind-pollinated and is a dominating pollen in its region. The pollens are highly allergenic. The seeds (fruit) ripen from summer. The fruit is an aggregate fruit, 1-5 cm long, and is white, becoming pink, and purplish to nearly black.
These trees are extensively grown in locations such as southern Europe and India for their leaves as food for silkworms. Mulberries are popular for street planting, and as ornamentals in the eastern US and in Europe. In some countries it is extensively cultivated along roadsides, in agricultural fields and in gardens. Having escaped, trees often appear on roadsides and along fencerows.
Fruits may be eaten raw or cooked. The wood is valued for sporting goods due to its elasticity and flexibility when steamed.
The family has small unisexual flowers, typical of nettle order to which it belongs, but its members are distinguished from other members of the order by the presence of milky sap containing latex. The female flowers are often borne inside the receptacle, which expands as the fruit matures, creating compound fruits. Other members are figs, bread-fruit and the American tropica rubber-tree (Castilia elastica).
In studies of the diurnal pollen periodicity, Morus shows an early morning pattern. It can be assumed that M. alba to varying degrees cross-reacts with other species of the same family, and cross-reactivity cannot be excluded with the elm family, Ulmacea. Furthermore, it is very likely that M. alba to a high degree cross-reacts with the Paper mulberry.
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Asthma, allergic rhinitis and allergic conjunctivitis occur following contact with pollen from this tree. (Navarro 1997 ref.5775 1)
Navarro AM, Orta JC, Sánchez MC, Delgado J, Barber D, Lombardero M. Primary sensitization to Morus alba. Allergy 1997;52(11):1144-5
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The relationships of asthma and allergic rhinitis with individual immediate skin test responses were examined for preferential associations and for changes with age in children raised in a semiarid environment. Immediate skin test responses to Bermuda grass were the most prevalent among children with allergic rhinitis and control subjects, whereas responses to the mold, Altenaria alternata, were the most prevalent among asthmatics. Skin test responses for crude house dust, Dermatophagoides farinae, and cat had low prevalences in all groups. Allergic rhinitis showed independent association with sensitization to Bermuda grass and mulberry tree pollen at age 11. The study concludes that Alternaria is the major allergen associated with the development of asthma in children raised in a semiarid environment and that skin test responses at age 6 are more closely linked to asthma than those at age 11. (Halonen 1997 ref.4810 8)
Halonen M, Stern DA, Wright AL, Taussig LM, Martinez FD. Alternaria as a major allergen for asthma in children raised in a desert environment. Am J Respir Crit Care Med 1997;155(4):1356-61
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Airborne contact urticaria due to Mulberry (Morus alba) pollen occurs. (Munoz 1995 ref.2584 3)
Muñoz FJ, Delgado J, Palma JL, Giménez MJ, Monteseirín FJ, Conde J. Airborne contact urticaria due to mulberry (Morus alba) pollen. Contact Dermatitis 1995;32(1):61
Information supplied from an abridged section of:
Allergy Advisor - Zing Solutions
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