Walnut, particularly Juglans regia (English or Persian walnut), has a long history of use in traditional medicine for various skin conditions, including psoriasis. In folk medicine, both the leaves and green husks of walnut have been applied topically or used in baths for their purported anti-inflammatory and antimicrobial properties. Historical texts from European and Asian traditions mention walnut preparations as remedies for chronic skin eruptions and inflammatory disorders. However, the specific evidence supporting its utility in psoriasis is based primarily on these traditional uses rather than rigorous scientific validation.

Scientific studies investigating walnut or its extracts for psoriasis are extremely limited. Some laboratory research has identified bioactive compounds in walnut leaves, such as juglone and polyphenols, which exhibit anti-inflammatory and antioxidant effects in vitro. Nevertheless, there are no robust clinical trials or animal studies directly evaluating walnut preparations in the treatment of psoriasis. The traditional use of walnut for skin ailments may be attributed to its general antimicrobial and soothing properties, but this does not equate to proven efficacy for a complex immune-mediated condition like psoriasis.

In summary, the rationale for using walnut in psoriasis management is grounded in traditional herbal practice rather than in scientific evidence. More research would be required to substantiate any specific therapeutic role for walnut in this context.