I want to do a permanent curl and tinting of eye lashes, which last for about 2 months. I am wondering if it will be a problem of Chatzitza for Mikvah?
If the tinting of the eyelashes is well maintained without noticeable gaps, there is room for leniency to Tovel with eye lash tint on.
Use only dye which has no independent substance to it, only colour, i.e. it is absorbed in the lashes and is not felt above the surface. Permanent dye is always less of a problem than semi-permanent. Tinting appointment should be scheduled long enough before Mikvah for the extra dye to be removed. Dye which remains on the face after treatment could be a Chatzitzah.
The dye should well maintained so she feels comfortable being seen in this condition. If it starts to fade, you can either reapply it and Toivel as it is whole or wash it off completely. If she does not like the way it looks, the dye is considered a Chatzitzah.
As far as we know, the tint can start fading from 2 to 4 weeks after the tinting. Therefore, this can be difficult to accomplish. If you commit to have them regularly maintained before Mikvah, this would be okay, but it is a strong commitment to make.
As an aside, it should be noted that many question the safety of eyelash tinting and it is not FDA approved.
Regarding the permanent curl, I understand that you mean to use chemicals that makes the hair curly. You should make sure before Mikvah that the hair is combed well and separated.
ראה שיעורי שבה״ל קצח, יז אות א ד״ה צבע. בדה”ש שם, קעט.