In recent months, an unusual accessory has been appearing more frequently on the wrists of guests at Madrid’s major events—bracelets capable of detecting dangerous substances in drinks. This innovation aims to enhance safety at city celebrations and festivals, which traditionally draw large crowds.
The Valencia-based company Celentis is behind the development of these bracelets. The system is simple: just dip your finger in the drink, apply a drop to a special area on the bracelet, and wait a few seconds. If the sensor changes color, that’s a warning sign that substances such as GHB, scopolamine (burundanga), MDMA, and other drugs used for chemical control are present in the liquid.
Celentis originated as a startup involving the Polytechnic University of Valencia and the University of Valencia. Initially, researchers developed reagents for detecting GHB and scopolamine, but the original format—liquid in vials—proved impractical for parties and concerts. In 2024, at the request of the regional government of the Valencian Community, a compact and discreet version was created—a bracelet resembling a festival pass, but with an integrated sensor.
Since then, tens of thousands of bracelets have been purchased by municipalities and government agencies. In Madrid, they have already been used at festivals in the Pinto and Chamberí districts. Each bracelet is equipped with one or two sensors: the orange one detects GHB, turning dark green in the presence of the substance, while the yellow one responds to compounds with an amine group, including ketamine, methamphetamine, scopolamine, and MDMA, and turns red when a drug is detected.
Although cases involving scopolamine are rare in Spain, it was added to the list in response to public demand. GHB is the most common substance found in the country, as it is easy to synthesize and its components are readily available, even through online stores.
Celentis mainly works with government agencies, but occasionally provides bracelets to public organizations and associations if they are unable to place a large order. The company emphasizes that the product serves an important social function and should be available where it is truly needed.
The bracelets are easy to use and require no special training. Simply apply a drop of the drink to the sensor to get a result. The system can detect even minimal concentrations of GHB—as low as 0.1 mg/ml—and the reaction is immediate. The bracelets are made from durable, waterproof Tyvek and can be reused if the sensor hasn’t been activated. The design can be customized for a specific event by adding a logo, a QR code with instructions, or even an NFC chip for payments within a festival.
In Pinto, bracelets were distributed at special information points during city festivals. If a suspicious substance is detected, organizers advise immediately contacting the police or calling 112. This measure is part of a comprehensive security program that includes entrance checks, canine units, and video surveillance.
According to the developers, the success of the bracelets can be attributed to their simplicity and effectiveness. They do not interfere with leisure activities, but allow everyone to maintain control over their own safety. The company plans to expand the distribution of bracelets and make them a common feature not only at city celebrations but also at concerts, clubs, and other crowded venues.
So far, no cases of drug detection using the bracelets have been reported in Madrid, but experts believe that their very presence serves as a deterrent. The ability to quickly test a drink reduces risks and restores people’s confidence in their safety at parties and festivals.
