Abstract: We included nine RCTs involving 2888 participants without occupational irritant hand dermatitis (OIHD) at baseline. Six studies, including 1533 participants, investigated the effects of barrier creams, moisturisers, or both. Three studies, including 1355 participants, assessed the effectiveness of skin protection education on the prevention of OIHD. No studies were eligible that investigated the effects of protective gloves. Among each type of intervention, there was heterogeneity concerning the criteria for assessing signs and symptoms of OIHD, the products, and the occupations. Selection bias, performance bias, and reporting bias were generally unclear across all studies. The risk of detection bias was low in five studies and high in one study. The risk of other biases was low in four studies and high in two studies. The eligible trials involved a variety of participants, including: metal workers exposed to cutting fluids, dye and print factory workers, gut cleaners in swine slaughterhouses, cleaners and kitchen workers, nurse apprentices, hospital employees handling irritants, and hairdressing apprentices. All studies were undertaken at the respective work places. Study duration ranged from four weeks to three years. The participants' ages ranged from 16 to 67 years. Meta-analyses for barrier creams, moisturisers, a combination of both barrier creams and moisturisers, or skin protection education showed imprecise effects favouring the intervention. Twenty-nine per cent of participants who applied barrier creams developed signs of OIHD, compared to 33% of the controls, so the risk may be slightly reduced with this measure (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.72 to 1.06; 999 participants; 4 studies; low-quality evidence). However, this risk reduction may not be clinically important. There may be a clinically important protective effect with the use of moisturisers: in the intervention groups, 13% of participants developed symptoms of OIHD compared to 19% of the controls (RR 0.71, 95% CI 0.46 to 1.09; 507 participants; 3 studies; low-quality evidence). Likewise, there may be a clinically important protective effect from using a combination of barrier creams and moisturisers: 8% of participants in the intervention group developed signs of OIHD, compared to 13% of the controls (RR 0.68, 95% CI 0.33 to 1.42; 474 participants; 2 studies; low-quality evidence). We are uncertain whether skin protection education reduces the risk of developing signs of OIHD (RR 0.76, 95% CI 0.54 to 1.08; 1355 participants; 3 studies; very low-quality evidence). Twenty-one per cent of participants who received skin protection education developed signs of OIHD, compared to 28% of the controls. None of the studies addressed the frequency of treatment discontinuation due to adverse effects of the products directly. However, in three studies of barrier creams, the reasons for withdrawal from the studies were unrelated to adverse effects. Likewise, in one study of moisturisers plus barrier creams, and in one study of skin protection education, reasons for dropout were unrelated to adverse effects. The remaining studies (one to two in each comparison) reported dropouts without stating how many of them may have been due to adverse reactions to the interventions. We judged the quality of this evidence as moderate, due to the indirectness of the results. The investigated interventions to prevent OIHD probably cause few or no serious adverse effects. Moisturisers used alone or in combination with barrier creams may result in a clinically important protective effect, either in the long- or short-term, for the primary prevention of OIHD. Barrier creams alone may have slight protective effect, but this does not appear to be clinically important. The results for all of these comparisons were imprecise, and the low quality of the evidence means that our confidence in the effect estimates is limited. For skin protection education, the results varied substantially across the trials, the effect was imprecise, and the pooled risk reduction was not large enough to be clinically important. The very low quality of the evidence means that we are unsure as to whether skin protection education reduces the risk of developing OIHD. The interventions probably cause few or no serious adverse effects. We conclude that at present there is insufficient evidence to confidently assess the effectiveness of interventions used in the primary prevention of OIHD. This does not necessarily mean that current measures are ineffective. Even though the update of this review included larger studies of reasonable quality, there is still a need for trials which apply standardised measures for the detection of OIHD in order to determine the effectiveness of the different prevention strategies.

Plain-language summary: We included nine studies in this review, involving 2888 male and female workers aged between 16 and 67. The studies included several types of workers: metal workers, dye and print factory workers, gut cleaners in swine slaughterhouses, cleaners and kitchen workers, hospital employees, and hairdressing apprentices. We were unable to find out whether or not the preventive measures were equally effective in all these professions because there were too few trials. The studies lasted from four weeks up to three years. Some of the preventive measures may reduce the risk of hand skin irritations. However, there were too few studies to be sure of this. The studies were too different from each other to combine in a meaningful way, and the results were too imprecise. Our results are therefore still debatable. Various barrier creams, moisturisers, and skin protection education programs were investigated. It is possible that barrier creams may slightly reduce the risk of developing OIHD. This result was based on four studies. In these studies, 29% of people who applied barrier creams developed hand skin irritations. In the control group, who did not apply barrier creams, 33% developed hand skin irritations. The results of three studies showed that moisturisers may reduce the risk of developing OIHD by a useful amount. Thirteen per cent of the people who used moisturisers developed hand skin irritations, compared to 19% of those who did not use moisturisers. Two studies showed that using a combination of barrier creams and moisturisers may reduce the risk of developing OIHD by a useful amount. Eight per cent of the people who used moisturisers and barrier creams developed hand skin irritations, compared to 13% of the control group. Based on three studies, we are uncertain whether skin protection education reduces the risk of developing OIHD. In these studies, 21% of the people who received skin protection education developed hand skin irritations, compared to 28% of the people in the control group. The safety and tolerability of these measures were not systematically addressed in these studies. However, no serious reactions to the treatments were reported. Mild reactions like itching or reddening of the skin were reported for only few people who applied the barrier creams or moisturisers. The measures to prevent hand skin irritations probably cause only few or no serious adverse effects. For barrier creams, moisturisers, or a combination of both, the quality of the evidence was low concerning the prevention of OIHD. There was not enough information and hand dermatitis was assessed differently across the studies. For educational programmes, the quality of the evidence was very low concerning the prevention of hand skin irritation. There was not enough information, hand dermatitis was assessed differently across the studies, and the studies were poorly conducted in some important respects. For the other key outcome, safety and tolerability of the treatments, the quality of the evidence was moderate because only indirect results were available.