Treatment of Atopic Eczema with Diet

Apart from elimination diets for the treatment of established atopic eczema 1, elimination diets based on placebo-controlled food challenges have also been tried. Although blind challenges have sometimes been performed in random sequence they are not the same as randomised controlled trials to determine the efficacy of elimination diets. Food challenges try to answer the question: Does food x make a particular child's atopic eczema worse? The precise relationship between such food challenge tests and the benefits of a long-term elimination diet is not clear. The summary addresses the evidence regarding: elimination diets, various supplementation products, such as fish oils, GLA, pyridoxine, zinc, vitamin E and multivitamins.

Reviewers' conclusions:

• None of the interventions and study populations were considered sufficiently similar to each other to warrant statistical pooling.
• Elimination diets are difficult for families and patients to follow, even in the highly motivated environment of a clinical trial.
• Drop-out rates are particularly high for elimination diets and those containing hydrolysate milk substitutes.
• Those RCTs that employ a parallel design with an unblended normal control diet risk biasing the motivation and ancillary care in favour of the active group.
• Those studies that place all participants on exclusion diets and introduce the suspected offending food versus a control, risk introducing another allergen (e.g. soya) or introducing the suspected allergen (e.g. cows´ milk) in an altered and controlled way that does not mimic real life.
• Marked order effects suggest that the crossover study is not the best method of assessing the benefits of dietary exclusion.
• There is little evidence to support an egg- and milk-free diet in unselected atopic eczema patients.
• There is no evidence to support the use of an elemental- of few-foods diet in atopic eczema.
• There is some evidence that the addition of a probiotic such as Lactobacillus may be beneficial for atopic eczema in those already on cows´ milk whey hydrolysate diet, though in the absence of a control group on no special diet it is hard to say if this is a real benefit.
• There is some evidence to support the use of an egg-free diet in infants with suspected egg allergy who have positive specific IgE to eggs in their blood.
• Methodological concern such as poor concealment of randomisation allocation, lack of blinding and high drop-out rates without an intention-to-treat analysis suggest that the above should be interpreted with great caution.
• Future studies should be longer term, more pragmatic and ensure that randomisation is concealed.
• If participant blinding is not possible, objective outcomes such as photographic records viewed by independent blinded observers should be used.

References

• Hoare C, Li Wan Po A, Williams H. Systematic review of treatments for atopic eczema. Health Technol Assess 2000;4(37):1-191. [PubMed]