BACKGROUND: Nickel and cobalt were not regarded as pertinent contact allergens in the hairdressing trade for the last decades. It was even stated that the relevance of nickel allergy in the hairdressing trade has been overestimated for several years. Recently, nickel and cobalt release from a multitude of metal tools in the German hairdressing trade was documented in two field studies.
METHODS: Review of two field studies.
RESULTS: In 2019, nickel release from 9.2% of 229 tested metallic hairdressing tools was evidenced, and in 2021, nickel release from 27.6% as well as cobalt release from 2.1% of 475 tested tools was detected in overall 30 North German hairdressing salons. Tweezers, sectioning clips, hair clips, and straight razors were identified as nickel as well as cobalt releasing tools. Crochet hooks and tail combs were identified as only nickel releasing tools.
CONCLUSIONS: A variety of metallic tools - which are used daily by hairdressers - release nickel and/or cobalt in allergologically relevant amounts. This circumstance has to be considered problematic with regard to the development of work-related allergic contact dermatitis. Thus, nickel and cobalt should possibly receive greater attention as potential contact allergens in the hairdressing trade.
CONCLUSIONS: The proven nickel and cobalt release from metallic hairdressing tools might entail legal ramifications in terms of insurance law. In case of nickel and cobalt allergies within the occupational group of hairdressers, metal tools might be considered as feasible sources for nickel and cobalt exposure.

BACKGROUND: It is well known that hard metal workers have historically been affected by contact allergy to cobalt. Knowledge is sparse about occupational skin exposure to cobalt, in terms of skin doses and sources of exposure, which could be used to improve protection of workers.
OBJECTIVE: To improve knowledge about skin doses and sources of skin exposure to cobalt within hard metal production, thereby facilitating better protection of workers.
METHODS: Forty workers were sampled on the index finger by acid wipe sampling after 2 hours of work. The samples were analysed with inductively coupled plasma mass spectrometry. Cobalt spot testing was performed in the work environment.
RESULTS: The highest skin doses were found among raw material workers. Skin doses among other production workers were also significant. Most office workers had low, but measurable, levels of cobalt on the skin. Glove use varied between workers. Cobalt was found on production equipment, on items in the canteen area, and on handles and buttons throughout the company.
CONCLUSIONS: Cobalt skin doses were prominent, and originated from contact with raw materials, sintered materials, and contaminated surfaces. Cobalt was present on surfaces outside production areas. Companies need to identify and reduce skin exposure for protection of workers.

BACKGROUND: In Korea, the prevalence of nickel allergy has shown a sharply increasing trend. Cobalt contact allergy is often associated with concomitant reactions to nickel, and is more common in Korea than in western countries.
OBJECTIVE: The aim of the present study was to investigate the prevalence of items that release nickel and cobalt on the Korean market.
METHODS: A total of 471 items that included 193 branded jewellery, 202 non-branded jewellery and 76 metal clothing items were sampled and studied with a dimethylglyoxime (DMG) test and a cobalt spot test to detect nickel and cobalt release, respectively.
RESULTS: Nickel release was detected in 47.8% of the tested items. The positive rates in the DMG test were 12.4% for the branded jewellery, 70.8% for the non-branded jewellery, and 76.3% for the metal clothing items. Cobalt release was found in 6.2% of items. Among the types of jewellery, belts and hair pins showed higher positive rates in both the DMG test and the cobalt spot test.
CONCLUSIONS: Our study shows that the prevalence of items that release nickel or cobalt among jewellery and metal clothing items is high in Korea.

BACKGROUND: A spot test was recently developed for easy and rapid testing to detect whether cobalt is available on surfaces in contact with skin.
OBJECTIVE: To explore the potential use of the cobalt spot test as a tool for skin dose assessment, and to verify the sensitivity under laboratory conditions.
METHODS: A cobalt dilution series (cobalt standards mixed with cobalt spot test reagent solution) was prepared to determine the threshold for colour change. Defined doses of cobalt were applied to the fingers of 5 volunteers. Acid wipe sampling was used to measure the recovery of applied cobalt skin doses on one hand, and cobalt-exposed areas on the other hand were spot tested.
RESULTS: A weak colour gradient was visible from approximately 1 to 1.5 µg cobalt/ml in the dilution series. For a skin dose of 0.125 µg cobalt/cm(2) , 80% of the cobalt dose was collected by acid wipe sampling. Spot tests gave positive results in all cases (n = 5).
CONCLUSIONS: The cobalt spot test can be used to show cobalt on the skin. More experience is needed to understand and describe the most suitable test conditions.