Scientists say this viral rosemary skincare trend actually works

"Many skin injuries end in scars, and in some people, it can lead to long-term cosmetic and even functional issues," said senior author Thomas Leung, MD, PhD, an associate professor of Dermatology at Penn. "Our findings suggest that rosemary extract, and specifically the antioxidant, carnosic acid, can shift the healing process from scarring to healthy skin regeneration. We don't have proven ways to consistently do that in humans."

A Viral Trend That Sparked a Scientific Question

Penn undergraduate student Jiayi Pang (left) and Penn PhD candidate Emmanuel Rapp Reyes (right) found that rosemary can help skin wounds heal without causing scars.

The idea for the project began on TikTok and Instagram. After noticing that many creators were promoting rosemary serums and rosemary-based products for better skin recovery, Pang and Rapp Reyes approached Leung to understand whether these claims had scientific merit. Their curiosity led them to begin a series of laboratory experiments.

"We hypothesized there was likely something real behind the hype because rosemary contains many antioxidants," said Pang, co-lead author of the study. "But we knew in order to really uncover its potential, we needed to prove its healing properties and uncover how exactly it was facilitating healing."

Testing Rosemary's Key Compound in the Lab

Working with mice, the research team created a cream made with carnosic acid, a naturally occurring antioxidant found primarily in rosemary. The cream sped up wound closure and helped regenerate structures such as hair follicles, oil glands, and cartilage. The scientists also found that the compound activated a skin nerve sensor known as TRPA1, which had previously been linked to the ability to heal without scars. When the cream was used on mice that lacked TRPA1, the treatment no longer produced the same regenerative effects.

"We also identified other herbs, such as thyme and oregano, that may activate TRPA1. But rosemary stood out for its potency and safety," said Rapp Reyes, co-lead author of the study. "Other natural ingredients, such as mustard oil, or the topical medication imiquimod are known to also stimulate the TRPA1 receptor, but unlike rosemary, those can cause irritation and inflammation."

Why Rosemary Works Only Where It Is Applied

The researchers discovered that rosemary's regenerative effect occurs only at the location where the carnosic acid cream is used. Applying the cream to areas of skin far from the injury did not lead to scar-free healing, emphasizing that its benefits are strictly local.

Potential for Future Wound Care Research

The Penn team advises people to speak with their healthcare providers before adding rosemary products to their skincare routine or creating homemade mixtures. Still, because rosemary is widely available and inexpensive, the researchers hope their findings encourage more exploration of its potential benefits in human wound care, especially for individuals prone to significant scarring.

"If rosemary is part of your skincare regimen and you think it's working, it likely is," said Leung. "I'm proud that the young scientists that led this research sought answers to questions in their everyday lives."