Background: Z. officinale and P. amarus are famous herbs and used as a traditional medicine for a long time. Both herbs have antiinflammatory and antioxidant properties. However, there is a few data on the development of herbal cream contained both Z. officinale and P. amarus extract (the combined extract) for dermal application.
Objective: The present study aims to investigate the acute and sub-acute dermal toxicity test of an herbal cream contained the combined extract in male and female Sprague-Dawley rats.
Material and Methods: The rats were randomly divided into the following three group: 1) control naive, 2) vehicle, and 3) 2,000 mg/kg. BW of the combined cream extract groups. The acute study, a single dose of 2,000 mg/kg.BW was applied at the dorsal of the back and determined the sensitivity and toxicity signs at 3 mins, 1 hr, 4 hr, 24 hr, 48 hr, 72 hr and at 14th day after a single application; the sub-acute study, repetitive treatments were applied 5 times/week, continually applied for 4 weeks. At the end of experiments, blood, skin, liver and kidneys were collected to evaluate hematological and histopathological effects.
Results: The herbal cream contained the combined extract did not cause skin irritation, inflammation and others abnormal signs at the contact area. Moreover, the herbal cream did not affect the growth of rats. No abnormalities were found in the organs and no adverse reactions were seen. The LD toxicity of both acute and sub-acute dermal test is greater than 2,000 mg/kg.BW.
Conclusion: The herbal cream contained the combined extract is highly safe for transdermal application for muscle injury and inflammation.

Keywords: Dermal toxicity test, P. amarus, Z. officinale