The90 Gem UV-tracking necklace review: how a $249 wearable revealed hidden UV exposure, heat sensitivity, and the limits of shade protection.
From Vanity to Vitality: A UV Tracker's Unexpected Lesson
When Sheena Vasani began testing the Gem, a $249 UV-tracking necklace from The90, her goal was simple: understand how sun exposure was aging her skin. But during an outdoor party in Los Angeles, with temperatures soaring into the 90s, the device delivered a wake-up call she didn't anticipate. Sitting under a patio umbrella with a fan nearby, she felt exhausted, dizzy, and nauseous—classic signs of heat exhaustion. Simultaneously, the Gem's companion app alerted her that UV exposure had climbed significantly, despite the shade. This moment sparked a deeper investigation: one of her medications increases heat sensitivity, explaining similar episodes over the years. The Gem didn't diagnose anything, but it prompted her to connect the dots between UV radiation, heat, and her own health.
How the Gem Works: Dual-Sensor Technology
Unlike basic UV forecasts that rely on location data, the Gem uses an onboard sensor to measure UVA and UVB radiation separately. This distinction is crucial: UVB is primarily responsible for sunburn and helps skin produce vitamin D, while UVA contributes to premature aging even without visible burning. The pendant itself is surprisingly stylish—a circular design on a thin titanium chain (gold- or silver-colored) that Vasani would wear even without tracking. Battery life lasted nearly a week, matching the advertised lifespan, and recharging is handled via an included dock. The90 plans to release a hat clip and bag tag early next year for those who prefer not to wear a necklace.
App Experience: Personalized Metrics and the Sun Score
The mobile app is central to the experience, offering easy-to-read graphs and jargon-light explanations. Users can create a skin profile—based on skin type, sensitivities, clothing, and sunscreen—to receive estimates for metrics like vitamin D production, circadian light benefits, nitric oxide-related benefits, cumulative UVA exposure, and recent accumulated UVA exposure. The app also provides a Skin Aging Zone assessment, personalized skincare advice, a sunburn countdown, sunscreen reminders, and a daily Sun Score. The Sun Score is a rating that balances sunlight's benefits against overexposure risks, with The90 encouraging users to aim for 90. However, Vasani found the individual measurements more revealing than the composite score. "Too little exposure means missing potential benefits, while excessive UV can damage your skin," she notes, appreciating the context but favoring the granular data.
The Bigger Picture: UV, Heat, and Health
Vasani's experience highlights a common misconception: shade alone doesn't guarantee UV protection. Radiation can be reflected or scattered by objects in the environment, meaning a patio umbrella offers limited defense. Moreover, UV exposure and overheating are distinct issues, yet both can impact health in overlapping ways. For Vasani, the Gem served as a catalyst for behavioral change—she now limits time outdoors during peak heat and UV hours, stays hydrated, and monitors how she feels. While her initial interest was vanity-driven (she started going gray in her 20s and wanted to slow visible aging), the device revealed a more profound truth: as an Indian woman with higher melanin content, she rarely sunburns, but that doesn't eliminate the risk of sun damage or skin cancer. The Gem's estimates, though predictions rather than direct measurements of bodily response, provided valuable awareness.
Verdict: A Niche Gadget with Real-World Impact
At $249 (often discounted to $149), the Gem is a niche product, but for those concerned about sun exposure—whether for aesthetic or health reasons—it offers actionable insights. The separate UVA/UVB tracking, personalized metrics, and sleek design make it a compelling wearable. However, users should remember that estimates are based on profiles and sensor readings, not direct biological feedback. As Vasani's story shows, the Gem's greatest value may lie in prompting users to ask questions they wouldn't have otherwise considered—about medication interactions, heat sensitivity, and the true reach of UV radiation. In a world where sun safety often focuses on appearance, the Gem reminds us that sunlight affects our health in ways both seen and unseen.