Any cosmetic products can cause reactions depending on individuals, and so does glue as well. "Sensitive glue" has the lowest irritation, however, it has the slowest drying time as well. It makes that most of the trainees use it for practicing purpose. The best way to lessen the reaction is to make your workplace well-ventilated. And do not apply the false eyelashes too close to your eyes. Most of all, if your clients have severe allergic reactions, having lash extensions is not recommended.