Colophony: Rosin in unmodified and modified form

Abstract

Colophony (rosin) is the non-volatile fraction of the oleoresins from coniferous trees, mainly pine trees. The composition varies depending on the source but also on the way it is produced. There are three types of rosin based on the way of recovery: gum rosin, wood rosin, and tall oil rosin. Rosin is present in unmodified and modified form in many products with various usages and is ubiquitous in our daily life. The main usages are printing ink, adhesives, and sealants, as well as paper size. Colophony (rosin) is a common cause of contact allergy and allergic contact dermatitis (ACD) based on its widespread usage and the skin sensitizing capacity. The main allergenic components are oxidized resin acids of the abietadiene-type which are formed on air exposure. 15-Hydroperoxyabietic acid was the first oxidation product identified as a contact allergen in gum rosin and is still considered to be the major sensitizer in colophony. Various allergenic compounds are also created in chemical modification processes performed to obtain improved technical rosin products. One of those is maleopimaric acid which is a strong contact allergen present in commonly used modified rosins. Studies on the prevalence of ACD caused by modified rosins and the major allergens should be performed in dermatitis patients and in the population. Colophony (rosin) has a harmonised classification as a skin sensitizer in category 1. This means that products containing rosin at a concentration of at least 0.1% should be labelled with the statement EUH208 - “Contains rosin; colophony. May produce an allergic reaction” and a safety data sheet is required. Products containing at least 1% rosin must be classified and labelled as “H317: May cause an allergic skin reaction”.