This is a very common minor complication of in office teeth whitening. If this happens to you, do not worry, your gingiva will go back to their original color in just a few days. Sometimes a small amount of whitening agent can leak past the gum barrier that is placed on your teeth during whitening. When this occurs, the gingival tissue can become blanched and look completely white in the spot where some whitening agent came in contact with your gums. This whitening is completely temporary and will return back to normal usually within 1 week. From a doctor's standpoint, you should have follow up scheduled so your treating doctor can check in on you and make sure your gingiva are back to normal. As a side note, if during your procedure you feel a lot of stinging or pain, it's important you bring this to your doctor's or the staff's attention, it may be necessary to discontinue the whitening procedure if it simply is too uncomfortable. Some patients have hypo mineralization and their teeth simply are not dense enough to withstand whitening, as such, they experience discomfort during whitening. These patients should not be doing whitening on their teeth, good luck!