Urticaria is a common skin disorder and 15-25% of people experience at least one attack of urticaria during their lifetime. Urticaria can be divided into acute urticaria (AU) and chronic urticaria (CU). CU is more common in adults, and affects women more frequently than men. According to Chinese medicine (CM) theory, CU is known as Yin Zhen. Nowadays, CM is widely used for managing CU in Hong Kong and mainland. Among different Chinese herbal formulae for urticaria, Xiao-Feng Powder (XFP), also known as Wind-Dispersing Powder, is one of the most frequently used Chinese herbal formulae for CU.

This study used modified Xiao-Feng Powder (mXFP) to evaluate the effectiveness and safety of mXFP in treating CU. Hence, a double-blind, randomised, placebo-controlled clinical trial design with strong scientific rigor will be employed in this study, and it would be able to provide robust clinical evidence on the efficacy and safety of mXFP for CU.

Urticaria is a common skin disorder and 15-25% of people experience at least one attack of urticaria during their lifetime. Urticaria can be divided into acute urticaria (AU) and chronic urticaria (CU) according to the disease duration. CU is classified as either chronic autoimmune urticaria or chronic idiopathic urticaria.

In Chinese medicine theory, Urticaria is usually associated with either internal or external wind pathogen. Wind as a pathogenic factor is characterized by sudden onset and rapid changes in symptoms, and when resulting from an internal deficiency, it often leads to dryness.

Several research groups have conducted clinical studies to evaluate the efficacy of Chinese herbal medicine for the treatment of CU in recent decades. Among different Chinese herbal formulae for urticaria, Xiao-Feng Powder (XFP), also known as Wind-Dispersing Powder, is one of the most frequently used Chinese herbal formulae for CU, also has been widely used in Chinese medicine dermatology to expel wind and eliminate dampness, clear heat, nourish the blood and stop itchiness. Moreover, other researchers have found that XFP is effective in inhibiting inflammation, allergy, and oxidative stress in allergic skin diseases.

Investigators hypothesize that mXFP is effective and safe for the treatment of CU. In this study, eligible subjects will be randomized to receive either mXFP or placebo twice daily for 12 weeks followed by post-treatment visits at week 16. Subjects will take the standard therapy of antihistamines regularly for the first 6 weeks and then on on-demand basis for the next 6 weeks during the treatment period.

Inclusion Criteria:

1. Both male and female;
2. Age from 18 to 65 years;
3. Documented history of CU for at least 6 weeks prior to entry in the study;
4. Meet EAACI/GA2LEN/EDF/WAO 2017 guidelines, i.e. spontaneous appearance of wheals, angioedema or both for > 6 weeks due to known or unknown causes;
5. Symptom severity must be greater than 10 points (UAS7 score);
6. Able to complete questionnaires and take medications as scheduled; and
7. Agree to participate in the study and sign the informed consent.

Exclusion Criteria:

1. Dual deficiency of Qi and blood according to Chinese medicine theory
2. Urticaria is induced by physical factors (e.g., cold urticaria, delayed pressure urticaria, solar urticaria, heat urticaria, vibratory angioedema) only;
3. Known to have dermatological diseases with skin pruritus;
4. Known to have any serious diseases such as cancer, severe kidney and liver impairments, autoimmune disease, thyroid disease, Hodgkin's disease, lymphoma, severe mental disorders, leukemia, and acute infectious disease;
5. Known to use oral/injectable corticosteroids, leukotriene inhibitors, immunosuppressants or other Chinese herbal medicine within one month of enrollment;
6. Known to receive omalizumab, ligelizumab, or other experimental biologic for CU;
7. Documented pregnancy or planning to conceive, breast-feeding women; or
8. Operate heavy machinery or need to drive motor vehicles as an essential part of their profession.
9. Know recent history (within previous 12 months) of drug addiction or alcohol abuse.
10. Involved in other interventional clinical studies at the same time.