Abstract: We included six RCTs (one with a cross-over design) randomising 310 children and reporting outcomes for 297 children. Most participants were aged under seven months with only two participants aged over one year (seven and 12 years old); where specified, 60% were boys. In two studies, condition severity was mild to moderate; one study included two participants with severe ISD; the other studies did not describe baseline severity or described it as body surface area affected. The study setting was not always clear but likely a paediatric outpatient clinic in the following countries: Thailand, Israel, USA, France, and Australia. Two studies compared oral biotin (a B group vitamin) against placebo, two studies compared proprietary products against placebo cream or a control shampoo, and two studies compared topical corticosteroids against other products. The studies were generally short-term, between 10 and 42 days' duration; only one study followed the participants until resolution of the rash or eight months of age. We assessed the risk of bias as unclear for most aspects due to lack of reporting, but two of the studies were at high risk of performance and detection bias due to the appearance of the intervention, the trial design (open-label), or use of overlabelled tubes. Two trials had a high risk of attrition bias. All the results given below were based on very low-quality evidence. Treatment duration ranged from one week to three weeks. For the two trials comparing biotin versus placebo (n = 35), one did not report a measure of change in severity (only change in duration of rash) while the other did not report raw data (only 'no statistically significant difference'), measured at three weeks. Neither trial reported on adverse events. Two trials compared proprietary products against placebo (n = 160). One trial assessed change in severity via percentage success (96% of participants in non-steroidal cream Promiseb versus 92% in placebo), and reported no adverse events (both assessed at day 14). The other trial assessed change in severity via reduction in lesional score (surface area covered), finding better results for lactamide MEA gel (a moisturising agent) plus shampoo (81.4%) compared with shampoo only (70.2%; P = 0.0092). No adverse events were described, but signs of discomfort were similar in both groups (both assessed at day 21). In the comparison of topical steroids versus another product, change in severity was measured through evaluation of cure and body surface (n = 102). In one trial comparing hydrocortisone 1% lotion with licochalcone 0.025% lotion, there was no significant difference in participants cured (95.8% with hydrocortisone compared to 97.1% with licochalcone). One person in the licochalcone group developed more erythema, but there were no other adverse events (both outcomes assessed at day 14). In the trial comparing flumethasone pivalate 0.02% ointment versus eosin 2% aqueous solution, a reduction in body surface area affected was seen in both groups at day 10 (9% with corticosteroid versus 7% with aqueous solution), with all infants showing less than 10% involvement. There were no adverse events (both outcomes assessed at day 10). No studies measured QoL. We found no trials testing commonly used treatments such as mineral oils, salicylic acid, or antifungals. Our review identified only a limited number of studies investigating the effects of interventions for ISD in infants and young children. Unlike the reviews investigating the effects of treatments in adults, our results showed that there is uncertainty regarding the effectiveness and safety of studied treatments due to the very low-certainty evidence for all comparisons and outcomes. We assessed most bias domains as at unclear risk, but there was a high risk of bias for (mainly) performance, attrition, and detection bias. Evidence was limited further by imprecision (small studies, low number of events), indirectness (mainly with the outcomes assessed), and poor trial reporting. In most studies, the prognosis for the condition was favourable regardless of intervention but interpretation is limited by the very low-certainty evidence. Further research is needed with large, well-conducted, and well-reported intervention trials, particularly of interventions commonly recommended or used, such as emollients or shampoos and brushing, antifungals, or steroids. All studies should report standardised and validated relevant outcome measures, including adverse events, severity, and QoL, and they should be conducted in primary care settings where the majority of ISD is managed. Future trials should compare against placebo, no treatment, or standard care.

Plain-language summary: We included six studies which were small with 310 infants, of whom 297 were included for analysis. The studies were short (10 to 42 days), and generally poor quality. Studies were in different countries, and, where stated, in paediatric clinics. Where stated in three studies, 60% were boys (144 boys among 241 infants). Most infants were aged under seven months; two were aged seven and 12 years. ISD severity where described was mild to moderate; one study included two participants with severe ISD. The treatments tested included: oral biotin (a B group vitamin) compared to placebo; trademarked creams or gels compared to placebo (or a control group); and steroid lotion or ointment compared to licochalcone (Chinese liquorice) cream and eosin (a red staining agent). Four studies had support from pharmaceutical companies: in three studies, a company supplied the intervention product; a company assisted with statistical analysis in one study; one employed a study author; and one had authors who were consultants to the pharmaceutical company. The evidence is current to 22 May 2018. Two trials assessed oral biotin versus placebo. One study only assessed duration of rash, and the other only reported that there was no differences between groups. Thus, it was unclear which treatment was more effective. In the two trials assessing trademarked skin products versus placebo, there was similar improvement in severity between Promiseb cream (96%) and placebo (92%). One trial assessed lactamide MEA gel plus shampoo versus shampoo only. Reduction of surface area covered and severity of rash was slightly higher in the gel group (81.4%) compared with shampoo only (70.2%). When comparing hydrocortisone 1% lotion with licochalcone 0.025% lotion in one study, cure rates, as a sign of severity, were also similar (95.8% with hydrocortisone versus 97.1% with licochalcone). Reduction in body surface area affected was similar when comparing flumethasone pivalate 0.02% ointment (9%) versus eosin 2% aqueous solution (7%). Only two trials reported side effects, including one case of increased skin redness with licochalcone, while in the study comparing lactamide MEA gel plus shampoo versus shampoo only there were no specific side effects reported. No studies measured improvement in quality of life. The quality of the evidence was downgraded to very low for all outcome measures in this review due to serious concerns with how the studies were conducted (risk of bias), how the outcomes were measured and reported, differences between the assessed treatments, and the small number of participants included. Thus, we cannot be certain of their accuracy.