Pigatto 1990.

Methods	Parallel‐group, randomised controlled trial (3 groups) This study was carried out in a secondary care setting at 1 centre in Italy
Participants	16+8 participants with dyshidrotic eczema (pompholyx) and positive patch test to nickel, confirmed by reaction on oral challenge with nickel No dropouts Inclusion criteria of the trial Hand eczema with palmar vesicles Type IV allergy to nickel at 5% pet Exclusion criteria of the trial Not defined Study population Gender: unclear; in the entire study 21 female, 3 male, although 8 participants in the control group should be excluded from the review Age: unclear; female from 23 to 45.3 years of age, male from 28 to 50 years of age
Interventions	Intervention • Low‐nickel diet for 3 months in 8 participants • Oral disodium cromoglycate (DSCG) 1500 to 2000 mg 3× daily for 3 months in 8 participants Control intervention • No treatment for 3 months in 8 participants ‐ not included in the review Duration 3 months
Outcomes	Primary outcomes of the trial Not defined Other outcomes Observer‐rated reduction in severity of itching: improvement/slight improvement/no improvement in degree of itching every 2 weeks Observer‐rated number of vesicles in an area (exact location not stated) of 2 × 2 cm every 2 weeks Nickel urinary levels at beginning and at week 4 Differences in intestinal permeability in a subgroup of 10 participants at day 0 and at day 15 Adverse events
Notes	Unclear which of the 2 is intervention and which is comparator. The third group consisted of participants who did not give consent for the interventions and was observed without undergoing any treatment. This group was not randomised and therefore was not included in the analysis Unclear how the outcome 'Degree of itching' was assessed. In addition, an intestinal permeability study was performed in 5 DSCG and 5 diet participants The secondary outcome ‐ reduction in severity, investigator‐rated ‐ was included but no reproducible data were provided The article states different numbers of participants included in intervention and control groups (8;8;8 vs 8;9;7) Declarations of interest: not stated Funding: not stated Sample size rationale: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "the patients were then randomly divided into 3 groups" Comment: groups 1 and 2 were probably randomised; however, the third group consisted of patients who did not give informed consent for the study and therefore were not randomised. Group 3 is not included in the analysis
Allocation concealment (selection bias)	Unclear risk	No details about how allocation was concealed from participants and clinicians
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "the patients avoided eating the foods indicated on a list, reduced the quantity of vegetables and of dairy products, and avoided using stainless steel utensils and ornaments" Comment: because the intervention group in group A had to follow a low‐nickel diet with strict dietary restrictions for 3 months, blinding was not possible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "the patients were evaluated blind by an observer...." Comment: observer blinded but no further details
Incomplete outcome data (attrition bias) All outcomes	Low risk	None of the participants dropped out, and all included participants were analysed (16 of 16 = 100%)
Selective reporting (reporting bias)	Low risk	No trial registration found. No major differences between Methods and Results sections
Other bias	Unclear risk	Baseline comparisons: no baseline analyses regarding group differences (randomisation check) Diagnostic certainty: yes The study was completed