| Common name: | Lichens |
| Botanical name: | There are more than 15,000 species of lichens, comprising 60 families with more than 400 genera. |
| Family: | Algae + fungus |
| Origin: | Lichens are widely distributed from the tropics to the high arctic and from the seashore to high altitudes. |
| Description: | Lichen are dual organisms composed of a symbiotic relationship between an algae and a fungus. The fungus, generally an ascomycete, gives the plant its shape, and the algae provides the capacity for photosynthesis. This successful combination is capable of producing a more elaborate and durable product. organism than either partner alone. Lichen can colonize inhospitable areas like bare rocks. As pioneer plants, lichens break the rock's surface and, together with the decaying material of lichen, eventually form suitable soil conditions for other plants. Many lichens are epiphytes (capable of growing on trees), drawing nourishment from the rain that falls down the tree trunks. Only a few species tolerate sulfur dioxide-contaminated air, so few survive in cities. Lichens are variable in shape, either tubular, vertical and branched, or flat and leaf-shaped or forming a amorphous grayish Cortex. |
| Applications: | Lichens are used as forage, particularly reindeer lichens: Cladonia raniferina, C. alperstris and C. sylvatica. Other forage species include Cetraria, Stereocaulon and Alectoria. Cetraria islandica has been turned into bread, porridge or porridge for human consumption. Lichens have been used in place of hops to brew beer and it was the basis of a large Swedish brandy industry in the 19th century; 10 kilograms of lichen producing five liters of alcohol at 50%. Lichen dyes were known for their high quality and color, but have largely been replaced by synthetic aniline dyes. Litmus paper was originally made by the Dutch from lichen. Since the 16th century, members of the Cladoniaceae, Stictaceae, Parmeliaceae and Usneaceae families have been used as raw materials in the perfumery and cosmetic industries. As manufacturing techniques improved, lichen extracts were combined into toilet powders and scented sachets. Today the main species that are still used in perfumery are Evernia prunastri (oak moss), E. furfuracea and several Ramalinae spp. |
| Allergens: | Usnic Acid, Atranorine, Evernic Acid |
| Allergy: | Allergic contact dermatitis. In 1907, a patient with crocodile hands ("crocodile net") in contact with chestnut bark was described. Lower-order plants (lichens) growing on trees were postulated to have been responsible for dermatitis. A report of a man who developed dermatitis to the side of his neck and ear after carrying freshly cut oak logs on his shoulder soon followed. A similar case was reported from Italy, where it was observed that the eruption He resorted each time when working with wood again. Since then, there have been numerous reports of lichen contact dermatitis growing on the bark of spruce (Abies), larch (Larix), and chestnut (Castanea). Most occupational contact dermatitis with lichens occurs in forest workers who have contact with lichens that grow on tree bark. The rash is generally limited to exposed skin Less obvious patterns may appear when lichens enter an open shirt and lodge at the waist line or when clothing is saturated with rain. Usnic acid is insoluble in water but is carried by tree trunks by rainwater and is present in the soil until degradation occurs. Lichen sensitivity can also develop from non-occupational contact with wood, for example, when transporting firewood at home or from contact with lichen while climbing a tree. Some ground lichens can also sensitize. A third of the "lichen gatherers" that harvest Cladonia stellaris, used in Christmas decorations, flower arrangements, toy trees in model railroad designs, etc., suffer from allergic contact sensitization. Other cases have been reported for arranging reindeer moss as Christmas decorations. Today, the main cause of lichen contact dermatitis is through exposure to perfumes containing oakmoss. |
| Cross reactions: | Several patients are allergic to lichens and liver. This probably represents multiple sensitizations, rather than cross sensitization, as both lichens and liverworts (Frullania) coexist on trees. The allergens in Frullania are sesquiterpene lactones that are probably not present in lichens. |
| Other information: | Theophrastus used the term Lichen (derived from the Greek leper) to describe superficial growth in the bark of olive trees. Initially, lichens also included liverworts (Hepaticae), but Diocorides attributed the term to true lichens because of its resemblance to the cutaneous disease (presumably lichen planus) for which they were supposed to be specific. The medicinal use of lichens dates back to the 18th dynasty (1700-1800 BC) when Evernia furfuracea it was first used as a drug. Herbal tradition often used plants that looked like a disease to treat that disorder. Xanthoria parietine, being yellow, it was supposed to heal jaundice, While Peltigera aphthosa, whose stem is dotted with small wart-shaped tubers, was recommended for children with thrush. The long strands of Usnea barbata were used to strengthen the hairAlthough Hippocrates prescribed it for uterine ailments. Boerhaven used Pulmonary lobaria for hemorrhage and asthma Other species of Evernia, Peltigera, Parmelia, Cladonia, Roccella and Pertusaria were used to control fevers, diarrhea, infections, skin diseases, epilepsy, seizures and as purgatives. New Zealand Maori dried and then reduced lichens or “Kohukohu” to powders for application to the skin rashes. 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; D-usnic acid 1%; 1% of Evernic Acid; Atranorine 0.5%; 2% Oak Moss; 1% of aesthetic acid; 1% acid smoking protocetraric |
Usnic acid contact allergy
Usnic acid allergy patch test
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