Tree of heaven (Ailanthus altissima) has a long history of use in traditional Chinese medicine and other folk medicine systems. It is commonly known as "chouchun" in Chinese medicine and has been used historically for a variety of ailments, including skin conditions such as rashes and hives (urticaria). The bark and leaves are the parts most often used, often in decoctions or topical applications. Traditional texts like the Shennong Bencao Jing and Compendium of Materia Medica mention its use for "heat" conditions, which can include skin eruptions, itching, and irritation.

However, modern scientific studies that specifically examine the efficacy of Tree of heaven for treating rashes or hives are lacking. Most research on Ailanthus altissima focuses on its antimicrobial, anti-inflammatory, and antimalarial properties, with only limited in vitro or animal model evidence for anti-inflammatory effects that might theoretically benefit skin conditions. There are no robust clinical trials or comprehensive pharmacological studies validating its effectiveness or safety specifically for rashes or hives in humans. Thus, while its use is justified by tradition, the scientific evidence is weak, and its efficacy for this indication remains unproven by modern standards.