How Do You Get Rid of Demarcation After CO2 Laser Resurfacing?

CO2 laser can cause hyperpigmentation or hypopigmentation. The goal of management is to determine which one you have and to treat the area accordingly. Fine telangiectatic blushing may also occur post laser or solar damage and this will also need to be treated, preferably with a pulse dye laser.
Fraxel, despite all of that is written about the laser, is not a cure all for all scars.

CO2 laser, when aggressively performed (as was often the case 10 years ago), destroys dermal pigment cells and the skin becomes lighter. Because the skin of the neck was not lasered, there is a demarcation.

By using fractionated laser at the jawline, you can sometimes blend the areas. Also fractionated laser in the neck and decollete as well can help to minimize the color difference.

Remember how deep the original CO2 was, so to get all your skin the same color, a similarly deep resurfacing would also be necessary. This is of course not indicated on the neck, and could risk scarring.

Loss of pigment is best avoided ahead of time by conservative resurfacing.

Your post will help many readers who are contemplating having phenol peels or deep peels of any type in an attempt to eradicate wrinkles, rather than to reduce wrinkles to a reasonable level but preserve natural architecture and pigment.

 

The demarcation line you experienced results from a loss of pigment in the laser treated area as opposed to the untreated area. There are several options to try to help the area but all would be aimed at decreasing the amount of pigment in the originally untreated area. This can be accomplished with a fractional CO2 laser or medium to deep chemical peel. The idea would be to feather the area to be treated for a more natural appearance.

Demarcation lines along the jaw lline do happen with all types of laser peels. The goals is to blend or feather the laser a bit so that the line is not distinct.  This still can be done for your situation in a similar fashion.

Unfortunately, little can be done to restore pigment to your facial skin. Although it is preferable to feather a CO2 laser procedure of the face with a light, single pass with a CO2 or Erbium laser of the neck at the time the face is treated, it might be worth trying the Fraxel re:pair which is a fractionated CO2 laser to the neck. Alternatively, a medium-depth chemical peel such as TCA 20% to the neck may feather and soften the demarcation line considerably.
Good luck.