The scent of fragrant lemongrass mingles with earthy ginger and tangy tamarind, punctuated by the sharp, menthol-like aroma of camphor. It’s a familiar smell for spa-goers: a traditional Thai herbal compress.

The treatment combines herbs in a cotton cloth, which is wrapped into a compact ball and steamed for around 10 minutes before the practitioner applies it to the body, typically after a massage.

Herbal compresses have been used for centuries for muscle aches, joint pain, and to reduce inflammation. However, it’s unclear how much benefit comes from the herbs: a 2015 review paper highlighted that the effects were mainly associated with heat, which increases blood flow and reduces pain.

While herbal medicine is a multi-billion industry that’s prevalent across the world, varying cultural practices, beliefs and knowledge have made it difficult to standardize or regulate. According to a report from the World Health Organization (WHO) in 2018, nearly half of member states did not have a national policy on traditional medicine, and only 64% had regulations on herbal medicines.

WHO says lack of research data is one of the biggest barriers to effective regulation.

In Thailand, the Center of Excellence in Applied Thai Traditional Medicine Research (CEATMR) at Thammasat University in Pathum Thani aims to provide research on the unique properties of the herbs used in herbal compresses and make this ancient remedy more accessible, says Arunporn Itharat, the center’s director.

Like other countries in Southeast Asia, alternative therapies are popular in Thailand, with surveys finding herbal medicine usage common among the population, particularly in rural areas. However, there’s a lot of traditional knowledge that needs to be scientifically proven, says Itharat.

“Herbs vary significantly in their properties, and this variability is one of the main challenges we face,” she says. “We need to validate the (extraction) process to ensure consistency across every batch.”

Another problem is that “a single herb can have many different varieties,” says Itharat, adding that “misidentification is a big issue in herbal medicine.”

In 2020, her research, published in the peer-reviewed Science & Technology Asia, found that some herbs can contribute to the efficacy of a herbal compress. “By isolating and testing each ingredient, the study identifies specific components contributing to the overall anti-inflammatory effect,” says Itharat.

The research center is applying traditional knowledge, such as the timing of harvesting the herbs, to make the extracts more effective.

For example, with zingiber montanum, a type of ginger known as “plai” in Thailand, “Elders have always emphasized that roots must be collected in the winter, when the plant has withered and its active compounds have concentrated in the roots,” says Itharat. This kind of traditional knowledge is often anecdotal and hasn’t been scientifically tested — so CEATMR is working to validate and standardize it.

“We can develop the extract into a finished medicine, making it more convenient to use, and we can control the quality,” says Itharat.