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Burn Skin from Optical Sensor

I have a burn on my wrist and I think the culprit is the optical sensor on my Garmin 935.

I have already considered that it may be a mechanical rash from the device rubbing me constantly, but I don't think so because this isn't my first sports watch and none have caused a rash on my skin in the past. Also, I clean the watch thoroughly after each activity so I know that it isn't caused by salt, sweat, or dirt. I really think it may be the senor burning my skin. I wear the watch constantly, but have switched it to my dominant wrist to see if the burn shows up on the other arm. I suspect it will.

I have no allergies and the 935 is plastic so I can't imagine what it could be if not the sensor burning my skin.

Has anyone else run into this? I have seen a couple of people post a similar issue either here or elsewhere; I even saw one with pictures identical to mine. I have not, however, seen resolution so I decided to ask. Please see the attached photo and let me know if you have a similar experience or whether you have the cause or "fix" for this issue.



  • rca411 We would recommend that you contact Product Support directly so that we can investigate this with you. You can contact a member of our Product Support team by email, phone, or chat.
  • I wear mine 24/7 and usually tighten and then forget to loosen after a run. I've had similar experiences in the past. I don't think the LED lights could cause a burn as they won't be putting out any UVA or UVB wavelength light.

    Probably just irritation:
  • Yeah, that's not a "burn" burn. Likely irritation caused by salt/sweat/soap getting trapped under there and rubbing against your skin. Every time I shower, I take my watch off, make sure to clean the area with soap, also use my thumb and wipe the sensor underneath the shower to clean off any salt/gunk that's on the sensor. Been wearing watches with optical sensors now for 4 years (Charge HR, Forerunner 235, now Forerunner 935), never had a rash.
  • FWIW for me the 'heat rash'-type-irritation makes wearing the FR935 on the same wrist 24/7 impossible unless on a one-piece Nato strap. No OHR anymore though. I'm disappointed, but should just have done better research before upgrading from a Fenix 3 - from what I hear it is quite a common issue.
  • A number of possibilities here:

    * A small percentage of people react to the nickel in stainless steel (eg. the Fenix 5 series), but it is less common with the plastic of the 935. Skin reaction to the resins in the OHR sensor are a possibility.
    * Buildup of bacteria (from sweat, etc) causing a skin infection (although I note you wash the watch regularly, and have used other sports watches).
    * The large watch size, 24/7 wear and the snug band required for effective OHR readings may mean that a patch of skin can't 'breathe', and creating some irritation. This may be different from your sports watch usage in the past. Personally, I have found some slight skin irritation with my Fenix 5 (on the side of the band, rather than the back of the watch), and have taken to removing the watch overnight, which has solved the problem.
    * UV burns - the extremely low power and green light wavelength of the LED's makes this very UNlikely.

  • from what I hear it is quite a common issue

    Not quite sure it's that prevalent, but it is hard to be certain. To be sure, posts crop up every now and then and 'inspire' a number of 'me too' replies. So is it a common issue? Who knows?

    Like others, I don't believe it's a burn as such. I suspect it's irritation cause by having the band tight enough to register HR that the sensor is pressed tightly against the skin. As it protrudes slightly, this is probably enough for air to be excluded thus allowing any bacteria to breed in a lovely moist and warm area. I don't wear mine 24/7 so can't really comment from experience though. However, on occasion I do feel some irritation from my Apple watch and the 935 if wearing for extended periods. I loosen the band a bit, allow some air in and the irritation goes away.
  • Wear mine 24/7. The worst I think i've even had was a burn-like red spot on the edge of my wrist from the band. Sweat + lots of muscle flexion + Summer heat=rash. No broken skin, just the rubbing. Never had a rash or burn from the bump ever, not even with my old Fenix 3hr.
  • I have experienced this "burn" a few times with my Fenix 3 which does not have the optical HR sensor.
  • I have it occasionally - I'm sure that it is not a "burn" I believe that it is just skin irritation. In the past I have always worn my watches quite loose so that the watch moves around on my wrist and the skin has plenty of space to breathe. With the OHR on the 935 to get sensible 24/7 monitoring the watch has to be snug. I always drop both my watch and cheststrap in the batch after every run whilst the batch is running. I then dry the watch (and my wrist) before putting back on. If I feel irritation starting then I swap the watch over to my other wrist overnight and usually find that is enough to allow me to switch back the following morning. In order to test if it is the OHR you should be able to switch it off for a few days and see if that makes any difference - I'd be very surprised if it did.