Intradermal administration of a killed Mycobacterium vaccae suspension (SRL 172) is associated with improvement in atopic dermatitis in children with moderate-to-severe disease

Background: Although a doubling in the prevalence of atopic disease, including atopic dermatitis, in the Western world over the last few generations has been paralleled by a marked reduction in infectious diseases, especially tuberculosis, it is unclear whether this increase in atopy is causally related to reduced exposure to mycobacteria. Objectives: The aim of this study was to determine whether administration of mycobacterial antigens to atopic individuals might ameliorate their disease. Methods: Forty-one children aged 5 to 18 years with moderate-to-severe atopic dermatitis were enrolled in a randomized, double-blind, placebo-controlled trial, where they were given either one intradermal injection of killed Mycobacterium vaccae (SRL 172) or buffer solution (placebo). Changes in skin surface area affected by dermatitis and dermatitis severity score were assessed before treatment and at 1 and 3 months after treatment. Results: Children treated with SRL 172 showed a mean 48% (95% CI, 32%-65%) reduction in surface area affected by dermatitis compared with a mean 4% (95% CI, -29% to 22%) reduction for the placebo group (P < .001) and a median 68% (interquartile range, 46%-85%) reduction in dermatitis severity score compared with 18% (interquartile range, -2% to 34%) for the placebo group (P < .01) at 3 months after treatment. There were no untoward effects of the treatment, apart from a local reaction in 13 of the 21 children, which occurred 1 month after SRL 172 administration and settled spontaneously. Conclusion: SRL 172 was associated with an improvement in the severity of the dermatitis in children with moderate-to-severe disease.