Some Apple Watch Series 12 and Ultra 4 owners report skin irritation under the sensors

Some owners of the new Apple Watch Series 12 and Apple Watch Ultra 4 say the watches are irritating their skin, describing redness, itching, and a burning feeling in the area directly under the sensors. The complaints have built up in a MacRumors Forums thread and on Reddit, and MacRumors rounded them up on October 7.

The experiences vary a lot. Several forum posters describe small red dots or a round red patch that lines up with the sensor array on the back of the watch. One Ultra 4 owner says mild irritation appeared after wearing the watch tighter than usual, lasted four or five days, and then cleared up. Another says Apple Support advised them to stop wearing their Series 12, and they returned it. Others report that wiping down the back of the watch and the band after workouts made the difference. There is no data on how many people are affected, and Apple hasn't commented on the reports.

What changed on the back of the watch

Both models use Apple's new Health Sensing System, which Apple describes as new optical and electrical heart sensors with larger green LEDs that sample heart rate every five seconds, all day. MacRumors notes the redesign also brings a larger ECG electrode surface and photodiodes arranged in a ring. That hardware is behind the accuracy gains testers have measured, including Quantified Scientist's comparison against a chest strap.

Some owners have wondered whether the more frequent readings or the new layout is to blame, but nothing so far ties the irritation to any single change. A recurring observation in the forum thread is that the new sensor sits flatter against the wrist, so sweat and residue build up faster and the back needs cleaning more often than on older models.

The materials touching your skin are the same as last year. According to Apple's materials list, aluminum Series 12 models have an aluminum back, as Series 11 did, titanium models keep a titanium back, the new ceramic models have a ceramic back, and Ultra 4 uses the same ceramic back as Ultra 3.

What Apple recommends

Apple's support guidance on wearing Apple Watch covers skin reactions in general:

• Fit: The watch should be snug but comfortable and sit above the wrist bone. A band that is too tight can cause irritation, and one that is too loose can rub. Apple suggests tightening the band for workouts and loosening it afterward.
• Cleaning: Keep the watch, band, and skin clean and dry, especially after workouts or contact with sweat, soap, sunscreen, or lotion.
• Materials: Aluminum and stainless steel cases, some band parts, and the magnets contain nickel below EU REACH limits. The case and many bands contain trace acrylates and methacrylates from adhesives, which Apple says are kept away from direct skin contact.
• If it persists: If you notice redness, swelling, or itchiness, Apple says to consult a physician before you put the watch back on.

If your watch is new enough to still be inside Apple's return window, 14 days in the US, returning it is an option if the irritation doesn't settle. Otherwise, Apple Support is the place to start. This is the second early-life issue for the new models after Apple shipped watchOS 27.0.1 to fix unexpected restarts.

Sources

• MacRumors, Juli Clover, "Apple Watch Series 12, Ultra 4 Owners Report Skin Irritation," October 7, 2026
• MacRumors Forums, "AW12 sensors causing skin irritation - Returning it"
• Reddit r/AppleWatch
• Apple Support, "Wearing your Apple Watch"
• Apple Newsroom, "Introducing Apple Watch Series 12, with the all-new Health Sensing System," September 9, 2026