Thymoquinone, the major active compound in Nigella sativa (black seed), has been studied for its anti-inflammatory and antioxidant properties, which have generated interest in its potential application for inflammatory skin conditions like eczema (atopic dermatitis). Several preclinical studies using animal models have demonstrated that thymoquinone can reduce inflammation, suppress pro-inflammatory cytokine production, and improve skin barrier function. For example, topical or oral thymoquinone has been shown in mice to decrease dermatitis severity, reduce histological signs of inflammation, and lower levels of IgE and inflammatory mediators relevant to eczema.

Human evidence is more limited. A small number of clinical studies have evaluated topical black seed oil (which contains thymoquinone) for atopic dermatitis, with some reporting mild improvements in symptoms compared to placebo or standard treatments. However, these studies often use whole oil preparations rather than isolated thymoquinone, and sample sizes are generally small. No large-scale randomized controlled trials specifically testing purified thymoquinone for eczema have been published as of 2024.

In summary, the scientific evidence supporting thymoquinone for eczema is preliminary, mainly based on animal studies and limited human data. While there is a plausible biological rationale and some supportive findings, the overall evidence quality is low, and more rigorous research is needed before recommending its routine use for eczema.