A group of students have invented a nail polish that changes colour when exposed to date-rape drugs.

'Undercover Colors' will enable a woman to "discreetly ensure her safety" by stirring her drink with her finger.

If the polish changes colour, the person will know "that something is wrong", the company explained.

The firm says it is the "first fashion company empowering women to prevent sexual assault".

The nail polish will change colour if date-rape drugs are detected. Credit: Undercover Colors

"While date rape drugs are often used to facilitate sexual assault, very little science exists for their detection," it said on its Facebook page.

"Our goal is to invent technologies that empower women to protect themselves from this heinous and quietly pervasive crime."

The company says it is the first fashion firm to empower women to prevent sexual assault. Credit: Undercover Colors

The concept was created by students Tyler Confrey-Maloney, Stephen Gray, Ankesh Madan, and Tasso Von Windheim, from the Materials Science and Engineering Department at North Carolina State University.

The students said all of them had been close to someone who had been sexually assaulted and they wanted to create a preventative measure to help protect women.

The students said they wanted to come up with a product to help protect women from sexual assault. Credit: Undercover Colors

"As we were thinking about big problems in our society, the topic of drug-facilitated sexual assault came up," Madan told Higher Education Works.

"All of us have been close to someone who has been through the terrible experience, and we began to focus on finding a way to help prevent the crime."

The students said they hoped the nail polish would deter potential perpetrators because of the fear they could get caught.

Undercover Colors was a runner-up in the K50 Startup Showcase and received $100,000 from an investor.

They have also received a $11,250 grant from the North Carolina State entrepreneurship initiative.

The students say their next challenge is to develop the product so it is suitable to be sold commercially.