There are three potential safety issues:
1. The eyelash extensions
Eyelash extensions are applied to your natural lashes about 1mm away from your skin. Synthetic eyelash extensions are not known to cause any allergic reactions or problems. It is possible to have real mink, fox, horse, and even human, eyelash extensions. Such natural products might in rare cases cause an allergic reaction in some people. (Although some extensions may be labelled ‘silk’ or ‘mink’ by their manufacturer, they may in fact be synthetic.)
2. The glue
The main ingredient of the glue used to attach eyelash extensions is cyanoacrylate . That is the bonding material. Occasionally, someone may be allergic to the glue and this will be usually be because they are allergic to the cyanoacrylate in the glue. The glue usually also contains carbon black, which is present to create the required dark, mascara-like colour. Occasionally, someone may be allergic to black carbon.
Eyelash glue reacts with moisture in the atmosphere to set. So if your eyes were open, fumes in the glue might react with moisture on your eyeballs to cause reddening. That’s why it’s important that your eyes are shut at all times.
3. The fitting
Having eyelash extensions fitted involves someone handling tweezers and glue very close to your eyes. So it’s important that you only have them done by a qualified eyelash professional. Applying eyelash extensions requires skill and precision.