Comparative light microscopic studies have revealed subtle differences between allergic and irritant reactions in the skin. In the search for specific differences, we focussed on the early inflammatory response. This pilot study was conducted to test the hypothesis that follicular spongiosis can differentiate between early allergic and irritant patch test reactions. 8 patients with known contact allergy to either colophony or quarternium-15 participated in the study. In each patient, allergic and irritant patch tests reactions were elicited, and 4-mm punch biopsies were taken after 6 8 h from clinically equipotent reactions. Paired sets of slides were assessed blindly by 2 pathologists. 1 patient showing a pityrosporum folliculitis was excluded from the study. All biopsies from allergic patch tests were characterized by follicular spongiosis, while biopsies from irritant patch tests showed no recognizable changes except a slight follicular spongiosis in 1 patient. The 2 pathologists agreed independently on the correct classification in 6 out of 7 cases (p=0.0156). We tested an optimized model, selecting non-irritant allergens and a well-known irritant. Further investigations are needed to elucidate the diagnostic significance of the histological classification of allergic and irritant cutaneous reactions in punch biopsies.

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We present 2 cases of allergic contact dermatitis caused by colophonium in Liquid Chalk, which is an adhesive product used for improving grip during pole dancing as a fitness exercise. CASE REPORTSCase 1: A 22-year-old woman was referred to the department because of dermatitis on the flexure of the elbows, popliteal fossa, abdomen, and thighs, corresponding to where she came into contact with the pole used for pole dancing. She had a history of dermatitis caused by band aids, stickers, and a colophonium-containing wart removal agent. Case 2: A 23-year-old woman who had been pole dancing for 1.5 years developed dermatitis in the popliteal region, thighs, upper arms, and neck, and behind the ears after pole dancing. The dermatitis subsided when she refrained from pole dancing. The patient had a history of atopic dermatitis in childhood and dermatitis caused by medical tape. Both women trained at a local sports centre by pole dancing on dry-coated metal poles (the manufacturer refused to divulge the composition of the dry coat; the poles, according to the patients, "most likely contained nickel"). To improve grip, Liquid Chalk with a high content of colophonium was used. Patch testing was performed with the European baseline series (TRUE Test Panel 1-3; SmartPractice/Mekos, Hillerød, Denmark) supplemented with additional allergens in Finn Chambers on Scanpor tape (SmartPractice, Phoenix, Arizona) for 2 days. Readings were performed on day (D) 3 and D7, according to published guidelines. 1The patients were both tested with colophonium, and case 2 was also tested with abietic acid 10% pet. Neither of the patients reacted to nickel, both patients had strong reactions to Liquid Chalk tested "as is" and colophonium, and case 2 also reacted strongly to abietic acid. DISCUSSIONColophonium is a well-known allergen in rosin-based adhesives, and abietic acid is regarded as the major allergen component. 2 It appears that the patients had both been sensitized by using band aids/medical tape. As a pleasant surprise, neither of the 2 young women was allergic to nickel. As nickel dermatitis related to pole dancing has been reported previously, this had actually been suspected. 3 Thus, it seems that the dry coat on the poles is an effective protectant. One patient had a history of atopic dermatitis. A distribution pattern vaguely reminiscent of atopic dermatitis in young women is an important clue to pole dancing-related dermatitis.