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Author: Dr Marius Rademaker, Dermatologist, Waikato Hospital, Hamilton, New Zealand, 2003.

Common name: Lichens
Botanical name: There are over 15,000 lichen species, comprising 60 families with over 400 genera.
Family: Alga + fungus
Origin: Lichens are widely distributed from the tropics to the high arctic and from the sea shore to high altitudes
Description: Lichens are dual organisms composed of a symbiotic relationship between an alga and a fungus. The fungus, usually an Ascomycete, provides the plant its shape, and the alga provides the ability to photosynthesis. This successful combination is able to produce a more elaborate and durable organism than either partner alone. Lichens are able to colonise inhospitable areas such as bare rock. As pioneer plants, lichens break down the rock surface and, together with decaying material from the lichen, eventually form soil conditions suitable for other plants. Many lichens are epiphytic (able to grow on trees), gaining nutrition from rain running down tree trunks. Only a few species tolerate air polluted with sulphur dioxide so few survive in cities. Lichens are variable in shape, either tubular, upright and branching, or flat and leaf-like or forming an amorphous greyish crust.
Uses: Lichens are used as fodder, particularly the Reindeer lichens: Cladonia raniferina, C. alperstris and C. sylvatica. Other fodder species include Cetraria, Stereocaulon and Alectoria. Cetraria islandica has been made into bread, porridge or gruel for human consumption. Lichens have been used instead of hops for brewing beer and was the basis of a large Swedish brandy industry in the 19th Century; 10 kilograms of lichen yielding five litres of 50% alcohol. Lichen dyes were renown for their high quality and colour but have largely been replaced by synthetic aniline dyes. Litmus paper was originally manufactured by the Dutch from lichens. Since the 16th century, members of the families Cladoniaceae, Stictaceae, Parmeliaceae and Usneaceae have been used as raw materials in the perfume and cosmetic industries. As manufacturing techniques improved, lichen extracts have been combined into toilet powders and scented sachets. Today the principal species still used in perfumery are Evernia prunastri (Oak moss), E. furfuracea and several Ramalinae spp.
Allergens: Usnic acid, atranorin, evernic acid
Allergy: Allergic contact dermatitis. In 1907, a patient with crocodile hands (‘mains de crocodile’) from contact with the bark of chestnut trees was described. It was postulated that the lower order plants (lichens) growing on the trees might have been responsible for dermatitis. A report of a man who developed dermatitis on the side of his neck and ear after carrying freshly cut oak logs on his shoulder followed shortly. A similar case was reported from Italy where it was observed that the rash recurred on each time on returning to work with wood. Since this time there have been numerous reports of contact dermatitis from lichens growing on the bark of firs (Abies), larches (Larix) and chestnuts (Castanea). Most occupational contact dermatitis to lichens occurs in forestry workers who have contact with lichens growing on the bark of trees. The rash is usually confined to exposed skin surfaces but less obvious patterns can occur when lichens get inside an open shirt and lodge at the waist-line or when the clothes are saturated with rain. Usnic acid is insoluble in water but is carried down tree trunks by rainwater and is present in the soil until degradation occurs.

Lichen sensitivity may also develop from non-occupational contact with wood, for example from carrying fire-wood at home or from contact with lichens whilst climbing a tree.

Some ground lichens can also sensitise. A third of ‘lichen pickers’ who harvest Cladonia stellaris, used in Christmas decorations, flower arrangements, toy trees in model railway layouts, etc, suffer from allergic contact sensitisation. Other cases have been reported from arranging reindeer moss as a Christmas decoration. Today the main cause of contact dermatitis to lichens is through exposure to perfumes containing oakmoss.
Cross-reactions: A number of patients are allergic to both lichens and liverworts. This probably represents multiple sensitisations, rather than cross-sensitisation, as both lichens and liverworts (Frullania) coexist on trees. The allergens in Frullania are sesquiterpene lactones which are probably not present in lichens.
Other information: Theophrastus used the term Lichen (derived from the Greek leprous) to describe a superficial growth on the bark of olive trees. Initially, lichens also included the liverworts (Hepaticae), but Diocorides ascribed the term to true lichens on account of their resemblance to the cutaneous disease (presumably lichen planus) for which they were supposed to be specific. The medicinal use of lichens can be traced back to the 18th dynasty (1700-1800 BC) when Evernia furfuracea was first used as a drug. Herbal lore often used plants which looked like a disease to treat that disorder. Xanthoria parietine, being yellow, was supposed to cure jaundice, while Peltigera aphthosa, the thallus of which is dotted with small wart-like tubercles, was recommended for children who suffered from thrush. The long filaments of Usnea barbata were used to strengthen the hair, although Hippocrates prescribed it for uterine ailments. Boerhaven used Lobaria pulmonaria for haemorrhage and asthma. Other species of Evernia, Peltigera, Parmelia, Cladonia, Roccella and Pertusaria were used to control fevers, diarrhoea, infections, skin diseases, epilepsy, convulsions and as purgatives.

The Maori of New Zealand dried and then reduced lichens or ‘Kohukohu’ to powders for application onto cutaneous eruptions. The active ingredient, like that of the Chinese drug ‘shi-hoa’ and the Japanese ‘seki-ka’, is usnic acid which is known to be antibacterial.
Patch test: Lichen (specific plant) as is; 1% D-usnic acid; 1% Evernic acid; 0.5% Atranorin; 2% Oak moss; 1% stitic acid; 1% fumarprotocetraric acid

Contact allergy to usnic acid



  • Gilbert, O. L., Lichens as indicators of air pollution in the Tyne Valley, in Ecology and the Industrial Society, Goodman, G. T., et al., Eds., Blackwell, Oxford, 1965, 35.
  • Ainsworth, G. C., Ainsworth and Bisby's Dictionary of the Fungi, 6th ed, Kew, Commonwealth Mycological Institute, 1971.
  • Ahmadjian, V., A guide to the algae occurring as lichen symbionts: isolation, culture, cultural physiology and identification, Phycologia, 6, 127, 1967.
  • Bylicka, H., Antibiotics of lichens, Acta Microbiol Polon, 1, 185, 1952.
  • Kerry-Nicholls, J. H., The origin, physical characteristics, and manners and customs of the Maori race, from data derived during a recent exploration of the King Country, New Zealand, J R Anthrop Inst, 15, 187, 1886.
  • Shibata, S., Relation between chemical constitution and antibacterial effects, of usnic acid and its derivatives, J Pharm Soc Japan, 68, 298, 1948.
  • Perez-Llano, G. A., Lichens. Their biological and economic significance, The Botanical Review, 10, 1, 1944.
  • Arctander, S., Perfume and flavor materials of natural origin, Elizabeth, N.J. Publ. by author, 1960.
  • Lovell, C. R., Plants and the Skin, Blackwell Scientific Publications, Oxford, 1993.
  • Mitchell, J. C., Maibach, H. I., Sensitizing capacity of usnic acid derived from lichenized fungi, Acta Derm Venereol, 49, 498, 1969.
  • Mitchell, J. C., Shibata, S., Immunologic activity of some substances derived from lichenized fungi, J Invest Dermatol, 52, 517, 1969.
  • Thune, P., Allergy to lichens with photosensitivity, Contact Dermatitis, 3, 213, 1977.
  • Thune, P., Solberg, Y. J., Photosensitivity and allergy to aromatic lichen acids, Compositae oleoresins and other plant substances, Contact Dermatitis, 6, 64, 1980.
  • Thune, P., Solberg, Y., McFadden, N., Staerfelt, F., Sandberg, M., Perfume allergy due to oak moss and other lichens, Contact Dermatitis, 8, 396, 1982.
  • Asahina, Y., Shibata, S., Chemistry of Lichen Substances, Japanese Society Promotion of Science, Tokyo, 1954.
  • Culberson, C. F., Chemical and botanical guide to lichen products, Chapel Hill, University of North Carolina Press, 1969.
  • Dahlquist, I., Fregert, S., Atranorin and oak moss contact allergy, Contact Dermatitis, 7, 168, 1981.
  • Gonçalo, S., Contact sensitivity to lichens and Compositae in Frullania dermatitis, Contact Dermatitis, 16, 84, 1987.
  • Gonçalo, S., Cabral, F., Gonçalo, M., Contact sensitivity to oak moss, Contact Dermatitis, 19, 355, 1988.
  • Fernandez de Corres, L., Photosensitivity to oak moss, Contact Dermatitis, 15, 118, 1986.
  • Fernandez de Corres, L., Leaniz Barrutia, I., Munoz, D., Bernaola, G., Fernandez, E., Audicana, M. T., Multiple sensitizations to plants in a farmer, Contact Dermatitis, 17, 315, 1987.
  • Fregert, S., Dahlquist, I., Patch testing with oak moss extract, Contact Dermatitis, 9, 227, 1983.
  • Hahn, M., Lischka, G., Pfeifle, J., Wirth, V., A case of contact dermatitis from lichens in southern Germany, Contact Dermatitis, 32, 55, 1995.
  • Lorenzi, S., Guerra, L., Vezzani, C., Vincenzi, C., Airborne contact dermatitis from atranorin, Contact Dermatitis, 32, 315, 1995.
  • Quirino, A. P, Barros, M. A., Occupational contact dermatitis from lichens and Frullania, Contact Dermatitis, 33, 68, 1995.
  • Pecegueiro, M., Menezes-Brandao, F., Airborne contact dermatitis to plants, Contact Dermatitis, 13, 277, 1985.
  • Robertson, W. D., Mitchell, J. C., Allergic contact and photodermatitis, Can Med Assoc J, 97, 380, 1967.
  • Sandberg, M., Thune P., The sensitizing capacity of atranorin, Contact Dermatitis, 11, 168, 1984.
  • Tan, K. S., Mitchell, J. C., Patch and photopatch tests in contact dermatitis and photodermatitis, a preliminary report of investigation of 150 patients, with special reference to "cedar-poisoning", Can Med Assoc J, 98, 252, 1968.
  • Thune, P., Eeg-Larsen, T., Contact and photocontact allergy in persistent light reactivity, Contact Dermatitis, 11, 98, 1984.
  • Wennersten, G., Photodynamic reactions induced by compounds derived from lichens, Acta Derm Venereol, 59, 197, 1979.
  • Thune, P., Contact allergy due to lichens in patients with a history of photosensitivity, Contact Dermatitis, 3, 267, 1977.
  • Hausen, B. M., Emde, L., Marks, V., An investigation of the allergenic constituents of Cladonia stellaris (Opiz) Pous & Vezda ('silver moss', 'reindeer moss' or 'reindeer lichen'), Contact Dermatitis, 28, 70, 1993.
  • Mitchell, J. C., Stereoisomeric specificity of usnic acid in delayed hypersensitivity, J Invest Dermatol, 47, 167, 1966.
  • Thune, P., Solberg, Y. J., Photosensitivity and allergy to aromatic lichen acids, Compositae oleoresins and other plant substances, Contact Dermatitis, 6, 81, 1980.
  • Heine, A., Tarnick M., [Allergic contact eczema caused by usnic acid in deoderant sprays], Dermatol Monatsschr, 173, 221, 1987.
  • Salo, H., Hannuksela, M., Hausen, B., Lichen picker's dermatitis (Cladonia alpestris (L.) Rab.), Contact Dermatitis, 7, 9, 1981.
  • Dahlquist, I., Fregert, S., Contact allergy to atranorin in lichens and perfumes, Contact Dermatitis, 6, 111, 1980.
  • Horand, R., Mains de crocodule, dermatose professionelle produite par le bois de chataignier, Gaz Hop, 80, 255, 1907.
  • Spillmann, L., Dermite artificielle due è l'action du chêne, Bull Soc Franc Derm Syph, 6, 33, 1921.
  • Tommasi, L., Dermite dei boscaiuoli de ipersensibilita, Giornale Italiano di Dermatologie, 70, 1223, 1929.
  • Dubreuilh, W., L'eczéma des bûcherons, Ann Derm Syph , 7(S.2), 199, 1931.
  • Spillmann, L., Weis, N., Deux cas de dermite artificielles dues veraisemblablement à l'action de substances vágétales chez le bûcherons, Bull Soc Franc Derm Syph, 38, 339, 1931.
  • Senear, F. E., Dermatitis due to woods, J Am Med Ass, 101, 1527, 1933.
  • Tenchio, F., Etiologie de l' eczèma des bucherons, Dermatologica, 97, 72, 1948.
  • Champion, R. H., Wood-cutter's disease, contact sensitivity to lichen, Br J Dermatol, 77, 285, 1965.
  • Mitchell, J. C., Armitage, J. S., Dermatitis venenata from lichens, biology of lichens related to criteria for diagnosis of occupational dermatitis and to industrial exposure risk, Arch Environ Health, 11, 701, 1965.
  • Mitchell, J. C., 'Cedar poisoning' and lichen allergy, Br Columb Med J, 7, 489, 1965.
  • Mitchell, J. C., Allergy to lichens. Allergic contact dermatitis from usnic acid produced by lichenized fungi, Arch Dermatol, 92, 142, 1965.
  • LeCoulant, P., Lopes, G., Wood dermatitis. Experimental research on the allergy due to mosses, J Med Bordeaux, 133, 245, 1956.
  • Mitchell, J. C., Schofield, W. B., Singh, B., Towers, G. H., Allergy to Frullania. Allergic contact dermatitis occurring in forest workers caused by exposure to Frullania nisquallensis, Arch Dermatol, 100, 46, 1969.
  • Mitchell, J. C., Fritig, B., Singh, B., Towers, G. H., Allergic contact dermatitis from Frullania and Compositae. The role of sesquiterpene lactones, J Invest Dermatol, 54, 233, 1970.
  • Mitchell, J. C., Dupuis, G., Geissman, T. A., Allergic contact dermatitis from sesquiterpenoids of plants. Additional allergenic sesquiterpene lactones and immunological specificity of compositae, liverworts and lichens, Br J Dermatol, 87, 235, 1972.
  • LeCoulant, M. P., L'allergie au Frullania, son role dans la "Dermite du Bois de Chêne", Bull Soc Franc Derm Syph, 73, 440, 1966.
  • Mitchell, J. C., Industrial aspects of 112 cases of allergic contact dermatitis from Frullania in British Columbia during a 10-year period, Contact Dermatitis, 7, 268, 1981.
  • Knoche, H., Ourisson, G., Perold, G. W., Foussereau, J., Maleville, J., Allergenic component of a liverwort, a sesquiterpene lactone, Science, 166, 239, 1969.
  • Champion, R. H., Atopic sensitivity to algae and lichens, Br J Dermatol, 85, 551, 1971.
  • Gonçalo, S., Born, M., Pereira dos-Santos, A. P., Contact dermatitis due to lichens, Contact Dermatitis, 7, 118, 1981.
  • Wood, B., Rademaker, M., Allergic contact dermatitis from lichen acids, Contact Dermatitis, 34, 370, 1996.
  • Brasch, J., Jacobsen, P., Flechten und ihre Allergene, Allergologie, 14, 99, 1991.
  • Frosch, P. J., Pilz, B., Andersen, K. E., et al., Patch testing with fragrances, results of a multicenter study of the European Environmental and Contact Dermatitis Research Group with 48 frequently used constituents of perfumes, Contact Dermatitis, 33, 333, 1995.
  • Frosch, P. J., Pilz, B., Burrows, D., et al., Testing with fragrance mix. Is the addition of sorbitan sesquioleate to the constituents useful? Contact Dermatitis, 32, 266, 1995.
  • Johansen, J. D., Menne, T., The fragrance mix and its constituents; a 14-year material, Contact Dermatitis, 32, 18, 1995.
  • Angelini, G., Vena, G. A., Giglio, G. et al., Contact dermatitis due to cosmetics, J Appl Cosmetol, 3, 223, 1985.
  • Santucci, B., Cristaudo, A., Cannistraci, C. et al., Contact dermatitis to fragrances, Contact Dermatitis, 16, 93, 1987.
  • de Groot, A. C., Liem, D. H., Nater, J. P., van Ketel, W. G., Patch tests with fragrance materials and preservatives, Contact Dermatitis, 12, 87, 1985.
  • de Groot, A. C., van der Kley, A. M., Bruynzeel, D. P., et al, Frequency of false negative reactions to fragrance mix, Contact Dermatitis, 28, 139, 1993.
  • Garrett, R. M., Studies on some aspects of ascospore liberation and dispersal in lichens, Lichenologist, 5, 33, 1971.
  • Petterrson, B., Experimentelle Untersuchungen über die evenemochore Verbreitung der, Sporenflanzen Acta Bot Fenn, 25, 1, 1940.
  • Philippe, J., Guibert, L., Combes, R., Considérations sur les allergies sylvaines, Rev Fr Allergol, 5, 95, 1965.
  • Fernandez de Corres, L., Munoz, D., Leaniz Barrutia, I., Corrales, J. L., Photo contact dermatitis from oak moss, Contact Dermatitis, 9, 528, 1983.
  • Mitchell, J. C., Absence of psoralen-type phototoxicity from usnic acid, some lichens, and lichen substances, J Invest Dermatol, 47, 61, 1966.
  • Thune, P., Lichens, compositae and photosensitivity, Photodermatol, 4, 1, 1987.
  • Held, J. L., Ruszkowski, A. M., Deleo, V. A., Consort contact dermatitis due to oak moss, Arch Dermatol, 124, 261, 1988.
  • Rafanelli, S., Bacchilega, R., Stanganelli, I., Rafanelli, A.. Contact dermatitis from usnic acid in vaginal ovules, Contact Dermatitis, 33, 271, 1995.
  • Schmidt, R. J., Allergic Contact Dermatitis to liverworts, lichens, and mosses, Semin Dermatol, 15, 95, 1996.
  • Krauskopf, J., [Contact hypersensitivity to Hypogymnia physodes],Cesk Dermatol, 51, 217, 1976.
  • Bhalme, A. Y., Pasricha, J. S., Irritant and sensitizing potential of some common Indian cacti, succulents, lichens and aquatic plants, Indian J Dermatol Venereol Leprol, 52, 89, 1986.
  • Guin, J. D., Jackson, D. B., Oakmoss photosensitivity in a ragweed-allergic patient, Contact Dermatitis, 18, 240, 1988.
  • Novak, M., Contact sensitisation to constituents of perfume composition in antiphlogistic ointment, Cs Derm, 49,375, 1974.
  • Favennec, F., Sensibilisation su lichen, à la Candidine et a Frullania, L'Ouest Médical, 27: 1647, 1974.
  • Favennec, M. J., Favennec, F., Les maladies cutanes en agriculture, L'Ouest Médical, 29: 395,1976.
  • Leonardi, G., Spore di lichens boschivo (Palmeria caperata) causa di al ergosi cutanea, Folia Allerg, 1: 219, 1954.
  • Champion RH. Dermatitis from pollens and lichens. Br J Dermatol 1969; 81: 869-70.
  • Thune, P., Sandberg, M., Allergy to lichen and compositae compounds in perfumes. Investigations on the sensitizing, toxic and mutagenic potential, Acta Derm Venereol Suppl (Stockh), 134, 87, 1987.
  • Rycroft, R. J. G, Menne, T., Frosch, P. J., Benezra, C. Textbook of contact dermatitis, Springer Verlag, Berlin, 1992.


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