Vitamin D supplements cut eczema severity by 11 points

Atopic dermatitis, the itchy inflammatory skin condition most people call eczema, can be stubborn to manage, and patients and parents are understandably drawn to anything safe that might take the edge off. Vitamin D has attracted particular research interest, built around two linked questions: do people with eczema actually carry lower vitamin D levels than healthy people, and does topping those levels up change how severe the disease is? Individual studies had pointed in different directions, so this review set out to pool everything available on both questions at once.

The authors searched the MEDLINE, EMBASE and Cochrane databases up to February 2018, retrieving 1085 articles and including sixteen. These covered observational studies comparing blood vitamin D, measured as 25-hydroxyvitamin D, between eczema patients and controls, plus supplementation trials that recorded baseline vitamin D and clinical severity using the SCORAD or EASI scoring systems. Eleven studies fed the comparison against healthy controls, and three trials fed the supplementation analysis. The average supplement dose across those trials worked out at 1500 to 1600 IU per day.

Eczema patients averaged 14 nmol/L less circulating vitamin D than healthy controls, and the gap widened to 16 nmol/L when only the studies in children were pooled. In the three supplementation trials, SCORAD severity scores fell by 11 points, exceeding by 22% the 9.0 point threshold treated as the smallest difference patients can actually feel. Improvements were greater in trials lasting three months. The supplementation finding rests on a small trial base, which is the main reason for caution.

This is an up-to-date pooling of a scattered literature, and it firms up two separate points: an association between eczema and lower vitamin D status, particularly in children, and a clinically meaningful severity reduction after supplementation in the trials run so far. What it cannot resolve is the direction of cause, since lower vitamin D in eczema patients could be a driver of disease, a consequence of it, or a marker of something else entirely. Three trials is also a thin base, and one author declares commercial interests in vitamin D related products, so independent replication matters.

If eczema is part of your life, this is a reason to think vitamin D status might be part of the picture, since the pooled data suggest levels run lower in this group. The supplementation result is genuinely encouraging because the improvement cleared the bar for a change patients would notice, not just a statistical one. But it comes from a handful of trials, so it is information to bring to a doctor rather than a settled treatment. Blood levels can be checked, which makes this one of the easier possibilities to investigate properly.