Allergic contact dermatitis (ACD) is an important disease that notably affects 14.5 million Americans each year.1 The economic impact of this disease is high in terms of both patient morbidity and loss of income, school and work and significant expenditures for visits to healthcare providers and for medicaments. A correct diagnosis of ACD will improve, prevent or “cure” the dermatitis and decrease overall costs to the healthcare system.1 Once patch testing is performed and a culprit has been identified, education becomes the critical intervention to ensure adherence to an avoidance regimen. With allergen avoidance, remission of the dermatitis ensues. Patients who are unable to comply with the avoidance regimen are at risk for recurrent or sustained dermatitis or progression to a systematized presentation.2,3
The 2 main types of contact dermatitis are irritant and allergic, with irritant contact dermatitis (ICD) being the most common. ICD may occur in anyone who is exposed to an irritating substance with significant duration or in significant concentrations such as chronic or frequent water exposure, abrasive cleansers, detergents and soaps. It is important to note that ICD can at times precede or be a concomitant diagnosis with ACD.4,5 ACD is a delayed-type IV hypersensitivity reaction that can occur to a large number of chemicals from poison ivy to fragrances in shampoos.
Epicutaneous patch testing provides a theranostic, or individual, assessment of each patient. Although ACD is not “curable,” many individuals will achieve complete remission with assiduous avoidance. In this section focus, we highlight ACD and explore top relevant allergens, regional-based dermatitis presentations, topic-based dermatitis presentations and clinical tips and pearls for diagnosis and treatment. This article focuses on colophonium.
History of the Tree’s Scab
Colophony surrounds us. It is in the makeup we apply to our faces, the tennis rackets we clutch and the cleaning products we use to scrub our homes. Colophony’s ubiquity likely contributes to its prevalence as one of the most common allergens in ACD.
Plant resins are uniquely different in composition from sap and other plant-based secretions. While saps have an intrinsic nourishing function (containing water, glucose, minerals and hormones), resins support the plant through important protective functions.6 Primarily, they ward off pathogens, insects and other animals by sealing puncture sites on the tree. This blocks entry for invasive organisms. The puncture wound could be secondary to an assailing animal or a blunt trauma from a neighboring tree. Sticky resins can also flush out or trap unwelcome organisms. The volatile turpentine oils of the secreted resin quickly evaporate. The remaining resin forms a scab. Additionally, resins have antiseptic and water retaining properties.7,8
Rosin (also known as colophony) is the term collectively used for the solidified, distilled form of resins from pines, cedars, spruce, firs and junipers. The proper name, colophonium, is noted by the International Nomenclature of Cosmetic Ingredients.9,10 Both names are derived from colophon. Colophon, which means summit, was an ancient city of Ionia, modern day Turkey. Colophon was situated along a ridgeline with surrounding pine trees. The term Colophonia resina has been traced back to these pines.7 Colophony is also known by several other names listed in Table 1.
There are 3 methods of procuring rosin, which result in different forms of rosin; all forms can cause ACD. Gum rosin is the most common form, which is obtained from live trees in the form of tapped fresh resin oils. These are then distilled to yield turpentine oil and gum rosin. Alternatively, dead pine stumps can be distilled to produce wood rosin. However, this labor-intensive method, with low yield, is the least common form of procurement. Lastly, tall oil rosin is a processed, liquefied byproduct of tree pulp. This pulp is more cellulose and used to make paper. Tall is Swedish for pine.11-13
The term “resin” that is also applied in modern day to denote synthetic resins, like epoxy, which share the physical property of being a thick liquid that hardens into a lacquer or enamel. However, that is the limit of the similarity, as these compounds have no relation to plant-derived resins.
Historical Notations on Colophony
Historically, mankind has long utilized resins for their sealant properties. In fact, rosin varnished and lacquered objects have been found in ancient cultures including Egypt, China and Japan. Prior even to its success as a varnish, it has been traced back to the Egyptian embalming methods of the Old Kingdom era (3050-2181 bc). Notably, through scientific analysis of ancient artifacts, it was discovered that they would soak strips of linen in rosin prior to molding them around the corpse.14 The researchers also noted that the Egyptians would often use powdered limestone in the mummification wrapping technique as a composite cement to improve adhesive properites.14
Interestingly in Genesis 6:14, Noah was instructed to “Make for yourself an ark of gopher wood; you shall make the ark with rooms, and shall cover it inside and out with pitch.” Pitch is a colloquialism for non-wood resources derived from conifers.15,16 Leonardo da Vinci is documented to have used colophony in a remedy for ailments. “A remedy for scratches taught me by the Herald to the King of France. Four ounces of virgin wax, 4 ounces of colophony, 2 ounces of incense. Keep each thing separate; and melt the wax, and then put in the incense and then the colophony, make a mixture of it and put it on the sore place.”17
Also, after decades of debate regarding the composition of the wood and the famous luthier Stradivarius’ methods, a 2009 study laid the query to rest by determining that the violins indeed contained a pine resin in the varnish.18 At the time, Stradivarius’ painting resin onto the wood of the violin’s body was novel and innovative — setting them above the rest and forever changing the sound of music. Today, it is common to apply rosin to the bows of stringed instruments. The reason resin is applied to the strings is to produce friction and augment vibration, and thus sound quality. In 1982, epoxy resins for bows were patented. This patent has lapsed and synthetic resins in bow making are now common.19
Stringed instruments are not the only area where rosin is frequently added to augment friction. In sports, colophonium is used to improve the traction of ballet shoe tips and racket handles.8 When allergy to wood products is in question, both the wood pulp and the varnish should be suspect.
Rosin is largely comprised of resin acids, namely abietic acid, dehydroabietic acid, neoabietic acid, dihydroabietic acid, palustric acid, levopimaric acid and pimaric acid.11,20 The specific balance of this mixture is dependent on the species of the tree, climate, method of extraction and how it is stored.21,22 The most common sensitizing resin acid is abietic acid.21,23
Colophony’s widespread applications exploit its properties of adhesion and hard enamel or lacquer finishes. These finishes require colophony to be first converted into solvents. It easily dissolves in alcohol or petrolatum, not water. These solvents can then be applied as a sealant paint layer. The non-resin compounds, typically turpentine oils, will soon evaporate, leaving the varnish.8
The spectrum of colophonium applications is immense (Table 2). Its pervasiveness likely contributes to its ranking as 1 of the top 10 allergens in many countries and make it an important source of occupational contact dermatitis.15,24,25 In the varnish industry, colophony is widely used. For example, a “light colored oak tree” toilet seat that was actually ash wood varnished with colophony to appear oaken was recently reported to trigger a localized buttock eruption that then generalized. The patient found resolution with a new non-wooden toilet seat.26
The 3 largest sources are paper printing industries, adhesives and varnishes.21,22 Pens and markers often incorporate colophony in the ink to prevent feathering and spreading.12 These have caused reactions at inked grids drawn for patch testing, which may limit the interpretation.27 There are some other important sources that may not be so obvious. For example, colophony has also caused airborne contact dermatitis, asthma, eye irritation and rhinitis.21,22,28 Furthermore, 3 documented sources of airborne contact dermatitis are linoleum floors, floor polish and a factory manufacturing dairy product cartons.28
Besides its use as a poultice for sores, dating back to da Vinci, colophony has been notably used in a wide range of medical applications, from the treatments for urinary problems, bronchitis and bone fractures, to boils, tinea corporis and rheumatism.29-31 In a recent report, a concoction named Tako-no-Suidashi, an old homeopathic remedy from Japan, was used to treat pustular skin dermatoses, such as carbuncles and cystic acne. Historically this salve contains a mixture, which is 31.5% rosin. In cases describing its use in cystic acne, side effects of significant facial erythema and edema are reported.11 Furthermore, an Italian woman developed generalized urticaria after applying an unnamed colophony containing homeopathic ointment to her wrist for tendonitis.21
In western medicine, colophony is commonly found in sutures, tape, dentistry products, namely sealants and topical medications.21 Cosmetics, including mascara, blush and lipstick potentially contain colophony. Much like ink, the colophony helps the makeup hold together and not “bleed.” Toiletries like dental floss, sunscreen and depilatories also commonly contain colophony. A recently reported source of colophony allergy is the absorbent core material of sanitary pads. The core materials may contain wood cellulose and or tall oil resin from spruce or pine trees.32 Glycerol esters of rosins may be applied to chewing gum as softeners.33
Recently in Turkey, neoprene thermal sauna shorts were reported to contain colophony. Because of this newly recognized source, it has been proposed that other neoprene products should be considered when assessing for colophony associated ACD. One of the principle components of neoprene surgical gloves is colophony. More specifically, they contain dehydroabietic acid. In neoprene, dehydroabietic acid is used in processing the aqueous dispersion of neoprene polymers into a gel.34-36
Sensitization and Testing
Patch testing is the diagnostic modality of choice in confirming a contact allergy to a number of agents. Colophony is included on the Thin-layer Rapid Use Epicutaneous test as 1200 mcg/cm2 of colophony, which corresponds to 972 mcg of colophony per patch. (T.R.U.E. Test, SmartPractice, Phoenix, AZ).13 The American Contact Dermatitis Society Core 80 allergen screening panel also includes colophony at a concentration of 20% in petrolatum.9
It is important to be aware of the increased prevalence of masked, yet relevant, contact allergies in patients with any component of the atopic triad (asthma, allergic rhinitis and atopic dermatitis). Colophony is one of the reported allergens of increased incidence in these patients. Therefore, avoidance of these allergens may improve their atopic-related conditions.37 Children with atopic dermatitis have a 41.3% to 52.6% incidence of contact allergies compared with 16% in children without.37-39 Table 3 identifies substances with cross-reacting components to colophonium.
Recall response is a lesser-known pearl of ACD. Exposure to a previously sensitized allergen cannot only induce an inflammatory response at the current site, but also at the previous sites of ACD to the particular substance.40 Patch testing can also elicit this response. Asking the patient about their chronic dermatitis severity during the patch test may be a clue that one of the positive results is clinically relevant.
Dr. Hamstra is clinical instructor in dermatology at Medical University of South Carolina, Department of Dermatology.
Dr. Jacob is the Section Editor of Allergen Focus and associate clinical professor and director of the Contact Dermatitis Clinic at Loma Linda University in Loma Linda, CA.
Disclosure: Dr. Hamstra reports no relevant financial relationships.
Dr. Jacob has served as an independent investigator on the safety and efficacy of T.R.U.E. Test™ (SmartPractice; Phoenix, AZ) panels 1.1, 2.1 and 3.1 in children and adolescents, Pediatric Research Equity Act (PREA-1) trial and now serves as an investigator on PREA-2. She has served as a consultant for Johnson & Johnson.
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