Birch bark
Birch bark or birchbark is the bark of several Eurasian and North American birch trees of the genus "Betula". The strong and water-resistant cardboard-like bark can be easily cut, bent, and sewn, which has made it a valuable building, crafting, and writing material, since pre-historic times. Even today, birch bark remains a popular type of wood for various handicrafts and arts. Birch bark also contains substances of medicinal and chemical interest. Some of those products (such as betulin) also have fungicidal properties that help preserve bark artifacts, as well as food preserved in bark containers . Collection and storage. Removing birch bark from live trees is harmful to tree health and should be avoided. Instead, it can be removed fairly easily from the trunk or branches of dead wood, by cutting a slit lengthwise through the bark and pulling or prying it away from the wood. The best time for collection is spring or early summer, as the bark is of better quality and most easily removed. Removing the outer (light) layer of bark from the trunk of a living tree may not kill it, but probably weakens it and makes it more prone to infections . Removal of the inner (dark) layer, the phloem, kills the tree by preventing the flow of sap to the roots. To prevent it from rolling up during storage, the bark should be spread open and kept pressed flat. Working. Birch bark can be cut with a sharp knife, and worked like cardboard. For sharp bending, the fold should be scored (scratched) first with a blunt stylus. Fresh bark can be worked as is; bark that has dried up (before or after collection) should be softened by steaming, by soaking in warm water, or over a fire. Uses. Birch bark was  a valuable construction material in any part of the world where birch trees were available. Containers such as wrappings, bags, baskets, boxes, or quivers were made by most societies well before pottery was invented. Other uses include: Birch bark also makes an outstanding tinder, as the inner layers will stay dry even through heavy rainstorms. Medical uses. On 22 April 2022, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Filsuvez, intended for the treatment of epidermolysis bullosa (EB ). The applicant for this medicinal product is Amryt Pharmaceuticals DAC. Filsuvez will be available as a gel for cutaneous use. The active substance of Filsuvez is birch bark extract (as dry extract, refined) from "Betula pendula" Roth/"Betula pubescens" Ehrh. (equivalent to 0.5‑1.0 g birch bark), including 84‑95 mg triterpenes calculated as the sum of betulin, betulinic acid, erythrodiol, lupeol and oleanolic acid. It is thought to work by modulating inflammatory mediators and stimulating keratinocyte differentiation and migration, thereby promoting wound healing and closure.