A systematic review 1 including 37 studies with a total of 1 676 subjects was abstracted in DARE. The interventions were topical applications of diphenylcyclopropenone DPCP (15 studies, 736 patients), dinitrochlorobenzene DNCB (8 studies, 264 patients) and squaric acid dibutyl ester SADBE (14 studies, 676 patients) as sole treatment. The types of AA were totalis or universalis, greater than 40%, less than 40% and other or mixed. Two of the studies were randomised placebo-controlled trials. Half-head studies were common, using half the patient's head as untreated control (n=14), treating half with the irritant sodium lauryl sulphate (n=1), or in one case treating initially only a single patch. The remaining studies were uncontrolled (n=15), had croton oil (n=1), tretinoin (n=1) or topical psoralen UV radiation A (n=1) as control treatment, or used combination treatment with interferon-alpha (n=1). Most of the studies were retrospective. The overall clearance rates of AA in the included studies ranged from 0 to 70% (median 30%). Side-effects were seen in up to 100% of the patients but subsequent withdrawal was uncommon.
Comment: The quality of evidence is downgraded by imprecise results (limited study size for each comparison) and by limitations in study quality and design. Placebo-controlled studies were unable to demonstrate any significant benefit in AA, but half-body studies showed advantage of immunotherapy over no treatment. In the treatment of AA, long duration of disease, extensive disease, young age at onset, a family history of AA, atopy, presence of nail changes and anergy are less likely to respond. It seems appropriate to reserve topical immunotherapy for very highly motivated patients who understand that there is limited evidence of treatment efficacy, and that the treatment can cause side-effects.
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