853 hard metal workers were patch tested with nickel sulphate 5%, potassium dichromate 0.5% and cobalt chloride 1%, each in petrolatum. Non-allergic reactions appeared in 6.5% of the nickel tests, 13% of the chromium tests and 18.3% of the cobalt tests. Most of the individuals with positive, poral or pustular reactions were retested with serial dilutions of metal salts in pet. and in water. The accuracy of a positive initial nickel reaction was 83%, a chromium reaction 40% and a cobalt reaction 62%. The nonallergic reactions were partly reproducible and correlated with both the type of patch test material and with individual factors. Weak and moderately strong positive patch test reactions to metal salts may be irritant and should be checked with serial dilution tests or at least be retested. A reduction of the cobalt chloride concentration from 1% to 0.5% in the standard test material is discussed.

Hard metal contains about 10% cobalt. 853 hard metal workers were examined and patch tested with substances from their environment. Initial patch tests with 1% cobalt chloride showed 62 positive reactions. By means of secondary serial dilution tests, allergic reactions to cobalt were reproduced in 9 men and 30 women. Weak reactions could not normally be reproduced. A history of hand eczema was found in 36 of the 39 individuals with reproducible positive test reactions to cobalt, while 21 of 23 with a positive initial patch test but negative serial dilution test had never had any skin problems. Hand etching and hand grinding, mainly female activities and traumatic to the hands, were found to involve the greatest risk of cobalt sensitization. 24 individuals had an isolated cobalt allergy. They had probably been sensitized by hard metal work, while the individuals, all women, who had simultaneous nickel allergy had probably been sensitized to nickel before their employment and then became sensitized to cobalt by hard metal work. A traumatic occupation, which causes irritant contact dermatitis and/or a previous contact allergy or atopy is probably a prerequisite for the development of cobalt allergy.

853 hard metal workers were examined and patch tested with 20 substances from their environment, including nickel and cobalt. Nickel sensitivity was found in 2 men and 38 women. 88% of the nickel-sensitive individuals had developed a jewelry dermatitis prior to employment in the hard metal industry or before the appearance of hand eczema. 29% of the hard metal workers gave a history of slight irritant dermatitis. In the nickel sensitized group, 40% had had severe hand eczema which generally appeared 6-12 months after starting employment. In 25% of the cases, nickel sensitive individuals developed cobalt allergy, compared with 5% in the total population investigated. Most facts indicate that nickel sensitivity and irritant hand eczema precede cobalt sensitization. Hard metal workers with simultaneous nickel and cobalt sensitivity had a more severe hand eczema than those with isolated cobalt or nickel sensitivity or only irritant dermatitis. 64% of the female population had pierced ear lobes. Among the nickel allergic women, 95% had pierced ear lobes. The use of earrings containing nickel after piercing is strongly suspected of being the major cause of nickel sensitivity. Piercing at an early age seems to increase the risk of incurring nickel sensitivity.

Of 368 patients with hand eczema examined during the years 1978-79, at a Department of Occupational Dermatology, 39% had a history of atopic disease (dermatitis, asthma, or rhinitis). 28% of the patients had or had had atopic dermatitis. The % of atopics in the patient material was highest in the age range 20-24 years, in which 57% of the patients had a history of atopic dermatitis, compared with only 11% in the age range above 35 years. Of all patients with a history of atopy, 22% had developed allergic contact dermatitis, while the corresponding figure for non-atopics was 45% (p less than = 0.001). Positive patch test reactions occurred in a significantly smaller number of individuals with past or present atopic disease than in non-atopics. Atopics had not changed jobs because of hand eczema to a greater extent, but had healed to a lesser extent after change of occupation than non-atopics (p less than 0.01).

A dermatologic investigation of 202 construction painters included patch testing with the TRUE Test standard series and ingredients of water-based paints, glues and putties (painters' series). 32 painters had current eczema and 16 had a history of previous eczema. Of these, 16 and 9, respectively, had current and previous histories of hand eczema. Irritant reactions on the hands, characterized by dry, erythematous finely fissured skin, which healed within a few days of skin rest, were found in 18 painters. 8 painters presented dry, fissured finger tips and finger sides. The total group of painters had 25 allergic reactions to the TRUE Test standard series and 11 to the painters' series. 11 test reactions were found to be related to present or previous hand eczema: 4 cases reacted to nickel, cobalt, colophony or N-octyl-isothiazolinone; 2 each to p-tertbutylphenol-formaldehyde resin and benzisothiazolinone (BIT); and 3 to Cl + Me-isothiazolinone. 5 painters were sensitive to BIT without clinical symptoms of skin disease. Hand eczema is no more common among construction painters who work with water-based paints, glues and putties, than in an average population. There are, however, special risks of sensitization and eczema in a construction painter's work that should be considered on employment.