Thymoquinone is the major bioactive compound in Nigella sativa (black seed) oil, which has been traditionally used for various inflammatory and skin disorders, including dermatitis. Scientifically, there is some preclinical evidence suggesting that thymoquinone has anti-inflammatory, antioxidant, and immunomodulatory properties that may be beneficial in inflammatory skin conditions. Several animal studies and in vitro experiments have shown that thymoquinone can reduce inflammation, modulate immune responses, and improve skin barrier function by downregulating pro-inflammatory cytokines and oxidative stress markers. For example, topical thymoquinone has been reported to decrease skin inflammation in mouse models of atopic dermatitis and contact dermatitis.

However, clinical data in humans are limited. Only a few small-scale studies have evaluated the effects of Nigella sativa oil (which contains thymoquinone) in patients with eczema or atopic dermatitis, showing modest improvement in symptoms, but these studies often lack rigorous controls and adequate sample sizes. No large-scale, randomized controlled trials specifically on purified thymoquinone for dermatitis have been published as of 2024. Thus, while some scientific basis exists, especially from preclinical research, the overall quality and quantity of clinical evidence are insufficient to strongly support its use for dermatitis at this time.