A finger in the glass, a color change, and a warning. That was the simple vision of a nail polish designed to detect specific drugs in a drink. Yet that very simplicity risked obscuring the most critical question: was there proof that it actually worked?

According to Joe Schwarcz of McGill University’s Office for Science and Society, the concept was discussed with far more certainty than warranted. In his article from March 20, 2017, he wrote that the nail polish was still merely a concept—not the finished invention the media coverage might suggest. His assessment is historical and does not document the current status of the technology today.

Molecules as Molds

Describing a reaction is not the same as proving that it works reliably.

Behind the idea, according to Schwarcz, lay a genuine chemical possibility. A polymer can be formed around molecules of the target substance. When the molecules are washed out, they leave behind cavities of a corresponding shape.

In the described model, these cavities are then filled with molecules of the same substance, linked to a dye. If the polymer encounters the drug in a drink, some of the embedded molecules can be displaced, releasing the dye. The idea was to embed this mechanism into nail polish.

It is an elegant idea. But describing a reaction is not the same as proving that it works reliably in a glass with mixed ingredients.

What a Lack of Color Change Does Not Tell You

Schwarcz highlighted that ingredients such as juice and milk could interfere with the reaction, and that the technology's reliability had not yet been properly established. Furthermore, a test targeting specific substances would not necessarily detect others. He pointed to ketamine and zolpidem, among others, as drugs that the solution in question would fail to detect.

Therefore, the absence of a color change cannot simply be translated into a drink being safe. What matters is not only what a test can detect, but also what it misses.

Safety Without Shifting Responsibility

The analysis also raised an ethical question: do such products risk implying that it is the potential victim's responsibility to detect an assault attempt?

A test can serve as an aid, but it must never become a benchmark for whether someone exercised sufficient caution. The story of the nail polish thus illustrates a broader challenge in science communication: the promise of protection should never outpace the evidence.