There are numerous case observations of allergic contact dermatitis to unmodified colophony in instrumental musicians, in particular string players such as violinists and cellists 13141516171819. Colophony dust may cause dermatitis of the fingers and hands, as well as of the face and neck. In 1930 Ramirez and Eller 13 first described a chronic fissured hand dermatitis of a violinist who applied colophony to the bow of his instrument. Wahlberg 14 found that 6 of 15 musicians allergic to colophony were also allergic to abietic acid. Colophony also known as rosin (INCI no. 280-192-2) is a naturally occurring material obtained from different species of coniferous tree (family Pinaceae). It is a complex mixture of resin acids and neutral substances. Abietic acid and its derivates are however thought to be the principal sensitizers of colophony 1516. Unmodified colophony is commonly used by string players (e.g., violin, viola, cello) to wax the strings in order to increase the attrition between the bow and the strings. There are many brands of colophony with various ingredients, so string players with sensitivities should find a different colophony that is better tolerated. For example, Nethercott and Holness 6 reported a 63-year-old male violinist with a 5-year history of an eczematous eruption on the left side of his neck. Patch testing revealed a strong reaction to colophony, both 20% and 60% in petrolatum. Despite his attempts to use as little colophony as possible, the eruption continued. In this case combination of fiddler's neck (see next paragraph) and colophony allergy was however likely. A musician may be exposed to colophony in numerous products including adhesive tapes, furniture polish, cosmetics, and varnishes as well. Moreover cross-reactions between turpentine, chrysanthemum, and balsam of Peru are well known.

Nickel, a common metal, is the most frequent contact sensitizer in the population at large. Nickel sensitivity has been observed in 4.5% in the general population, in 8% of females and 0.8% of males 2021. It plays a great role in contact dermatitis of musicians, as well, and may cause dermatitis of the fingers and hands, as well as of the lip and neck area. Nickel contact dermatitis has been reported in string players (e.g., violinists, cellists, guitarists) and wind and brass instrumentalists such as flautists and trumpet players 22232425262728293031. Woodwind or brass instrumentalists with nickel allergy may switch to gold or plastic mouthpieces. The release of nickel from metal devices is favored by friction, heat or galvanic factors. This may also happen during exposure to various bodily fluids including sweat and saliva. Consequently chronic mechanical irritation and maceration may not only cause irritant dermatitis but can also promote allergic contact eczema. Combined reactions to nickel, and chromium are not uncommon in the population at large and do present a simultaneous, distinct, and specific sensitization.

Marshman and Kennedy 24 reported a classic guitar player who experienced a dermatitis of the fingers due to a combined allergy to nickel and metal guitar strings. Notably, this affluent patient substituted 24-karat gold strings. Bronze, copper, nylon, or organic strings are available for less affluent, nickel-sensitive acoustic string instrumentalist. However there are not much alternatives for the common electric guitar or bass player who usually uses nickel-wound and stainless steel strings which are characterized by optimal electromagnetic properties (Fig. 1). Stainless steel used for thin strings such as the E-string of a violin or guitar is basically an iron-chromium solid solution alloy with nickel and other ingredients added to increase resistance to corrosion and pitting. Fisher 27 described a patient with an allergic cheilitis from nickel-plated harmonica. The patient had a strongly positive patch test reaction to nickel sulphate and the metallic parts of the instrument showed a strongly reaction to the dimethylglyoxamine test. Furthermore Ingue et al. 22 reported a 19-year-old female flautist who developed eczema on her chin 2 months after developing earlobe dermatitis from an earring. Inductively coupled plasma atomic emission spectrometry revealed that her flute contained 0.067% nickel, though a dimethylglyoxamine spot test on the flute was negative. Patch tests showed a positive reaction to 2.5% nickel sulphate in petrolatum. The authors discussed that their case was due to nickel sensitivity of the alloy enhanced by pressure, friction, and moisture of sweat, breath condensation and saliva. Accordingly, Moreno et al. 31 described a 24-year-old viola player who had developed allergic contact dermatitis to nickel that was contained in metal pieces of the chin rest – a similar case has also been reported by Pencelli 25.

A variety of exotic woods are present in musical instruments and may cause allergic contact dermatitis 3233343536373839. East Indian and Brazilian rosewood is used for manufacture of string and reed instruments such as violins, violas, guitars, recorders, and flutes. Makassar ebony and ebony woods are used for crafting violin and guitar fingerboards. Moreover Cocobolo wood and African blackwood are utilized for the production of recorder, oboe, and other reed instruments. For example, Hausen and Mau 35 reported a 19-year-old female violinist who developed an allergic contact dermatitis at her chin corresponding to the site of the wooden chin rest. The timber of the chin rest was identified botanically as an East Indian rosewood species (Dalbergia latifolia Roxb.). Patch tests with compounds of both standard series and ethanol extract of the chinrest wood revealed positive reactions. Accordingly, Haustein 38 described a case of allergic chinrest dermatitis to East Indian rosewood in a violinist. Furthermore Hausen et al. 323336 reported on allergic contact dermatitis in musicians (recorder player, violinist) that was caused by a rosewood substitute Machaerium scleroxylum (Pao ferro), Brazilian rosewood (Dalbergia nigra All), or Cocobolo wood (Dalbergia retusa), respectively. Patients should be advised of cross-sensitivity between similar woods containing structurally related allergens. For example, the sensitizing agent (R)-4-methoxydalbergione is present in Brazilian and East Indian rosewood as well as Cocobolo 37. For string players, boxtree wood has been recommended as an alternative chin rest wood because it does not contain any known allergens 9.

Several case reports on cane reed contact allergies in musicians have been reported 40414243. Ingoue et al. 40 described a 32-year-old man with a 6-month history of severe cheilitis that developed 2 months after starting to play the saxophone for a few hours several times a week. The patient showed scaly erythema with erosions and fissures on the median lower lip, and the distribution matched the area in contact with the saxophone cane reed which was made of the reed grass Arundo donax which is related to bamboo. The stems of the plants are used, for example, as lathes, for fishing rods, or in crafting of wind instruments such as saxophone or clarinette. Accordingly McFadden et al. 41 reported a similar case in a clarinetist who showed the same patch testresults. Apart from irritant contact dermatis, both immediate and delayed allergic aetiologies have been observed in cane reed cheilitis 40414243. Notably, an immediate-type allergic, contact urticaria-like reaction to a reed made of Arundo donax has been observed in an atopic saxophonist. This patient had a positve prick test but not patch test result 43. Plastic polysterene reeds are available for wind instrumentalists with cane reed hypersensitivity.

There have been few case reports of allergic contact dermatitis to propolis cera (INCI no. 288-130-6) in musicians and instrument makers 44454647. Liebermann et al. 44 described a case of a stringed instrument craftsman and violinist who developed allergic contact dermatitis to propolis, a component of Italian varnish. Besides, this patient had positive patch test results to colophony as well. Hausen et al. 46 reported that propolis has been used as an ingredient in violin varnish for centuries. Stradivari is said to have used it in the varnish of his instruments. Propolis, also known as bee glue, is produced by bees during hive construction to fill structural gaps. It has approximately 50 constituents, primarily resins and vegetable balsams (50%), waxes (30%), essential and aromatic oils (10%), and pollen (5%). Since ancient times, this agent has also been incorporated into numerous medical and cosmetic products since it is believed to be a potent antiseptic and anti-inflammatory substance, local anaesthetic, adstringent, and antioxidant. Moreover propolis may be found in toothpaste, mouthwash preparations, facial creams, chewing gum, polishes, and varnishes. Because string players such as violinists and cellists as well as stringed instrument makers may be significantly exposed to propolis in varnish, the differential diagnosis of a recalcitrant, chronic eczema in these individuals must include allergic contact dermatitis 45. Moreover, patients with an allergy to propolis may be at risk for cross-sensitization with balsam of Peru 47.

Bork 48 described skin eruptions on the neck of a violinist which have been caused by para-phenylenediamine allergy. Chin rests made of ebony wood that are black enough have been coloured with a stain containing "Ursol-Echtschwarz", which consists of para-phenylenediamine, a common allergen with cross-reactivity to parabens, benzocaine, and sulfonamides. Furthermore O'Hagen and Bingham 49 reported a 11-year-old cellist with dermatitis on the right thumb, index and middle finger of her right hand that held the bow. On patch testing she was positive on para-phenylenediamine which was used to stain her bow string.

Nethercott and Holness 6 reported a 25-year-old harpist with a 5-month history of an eczematous rash on the tips of her fingers on her right hand. Patch testing showed a strong reaction to potassium dichromate. The authors found out that this common allergen was used as a tanning agent for the strings of her harp. Buckley and Rogers 50 described a 30-year-old professional violinist who presented with a 3-year history of hand and foot dermatitis. It started on the left ring finger and spread to both hands and feet. Patch test revealed a strong reaction to potassium dichromate that was contained in the core of the E-string of his instrument. Changing the string to a type with a stainless or aluminium core resulted in rapid clearing of the dermatitis. Trivalent or hexavalent chromium is usually utilized for this purpose. Hexavalent chromium has greater sensitizing properties, since it readily penetrates the skin, in particular in sweaty conditions. As exemplarily demonstrated in Figure 1 and 2, string instrumentalists such as electric guitar and bass players are not only at risk to develop nickel but also chromate allergy due to intense contact to chromated steel components on their instrument (e.g., strings, bridge, frets). Besides chromated leather of instrument accessories such as guitar straps may also play a role in contact dermatitis of musicians 2150.

Many case observations have been reported on "fiddler's neck" 5152535455565758596061. Peachey and Matthews 51 systematically studied this condition that frequently affects violin and viola players. An area of lichenification and hyperpigmentation on the side of the neck below the angle of the jaw is usually observed in this skin disorder. Erythema, scaling, cyst and scar formation, papules and pustules, and even focal neck oedema may occur as well 515657. Recently dystrophic calcinosis cutis in the skin below the mandible has been described in a 29-year-old violinist 52. Histopathology of "fiddler's neck" frequently demonstrates hyperkeratosis, acanthosis and histiocytic infiltrates with presence of granulomas to foreign body and follicular cysts. Clinically, non-eczematous irritant contact dermatitis with granulomatous or acne-like appearance has previously been distinguished. Persistent or "dermal" irritant contact dermatitis may also be differentiated histopathologically from rosacea and sarcoid reaction with granuloma formation 62. Probably due to the particular location and relatively complex mechanism for causation of "fiddler's neck" the clinical appearance and histopathology of this skin condition show a wider spectrum of skin changes as compared to common irritant contact dermatitis 5062. Some authors believe that this condition belongs to the range of acne mechanica 53. The aetiology is thought to be due to a combination of factors: friction giving rise to lichenification, while local pressure, shearing stress, and occlusion may play a part in producing acne-like lesions and cyst formation. Additionally poor hygiene may predispose to local infection. Viola players are believed to be more prone to develop "fiddler's neck" than violinists because the instrument itself is larger and heavier 5159.

Similar irritant skin disorders such as "cellist's chest" and "cellist's knee" have also been described in cello players 763. Even a "cello scrotum" has been described in a brief letter 64. However this term has been questioned since the contact of the cello's body with the scrotum would require an extremely awkward playing position 65. Interestingly, Curtis 66 reported three girls with traumatic mastitis of one breast. The condition consisted of a slightly inflamed cystic swelling at the base of the nipple. All three patients were learning to play classic guitar on a full-sized guitar – the edge of the sound-box pressed against the nipple. Consequently the two right-handed patients had a right-sided mastitis and the left-handed patient a left-sided mastitis. This condition, also known as "guitar nipple" can easily be prevented by positioning the adequate instrument properly to reduce the amount of pressure placed on the nipple 676869.

In analogy to string players, woodwind and brass instrumentalists appear to be prone to develop irritant contact dermatitis on her lips and/or chin 7071727374. "Flautist's chin" has been described in a 32-year-old amateur flautist 70. She presented with an eruption of acne-like lesions and hyperpigmentation confined to the central mid-portion of her chin, where she was in contact with her flute. Wetting of the chin with saliva or breath condensate was suspected as a predisposing factor, as this slipperiness could cause the player to increase the pressure of the flute against the skin 73. Two separate reports of "clarinetist's cheilitis" have appeared in the literature 7072. Hindson 70, for example, reported three cases of an irritant contact dermatitis confined to the median area of the lower lip exactly underneath the reed of the clarinet. Results of extensive patch testing were negative. Friedman and Connolly 72 described the case of a 15-year-old clarinetist in whom erythema and scaling of the median portion of the lower lip developed. Again, results of extensive patch testing were negative. Both reports suggest that "clarinetist's cheilitis" may be caused by a combination of factors, including friction, local pressure, shearing forces, and occlusion 7. It has to be stressed, however, that atopic diathesis is a commonly overlooked cause of cheilitis 28.