Not many people know this but the glue used to attach eyelashes is one of the most toxic and least healthy things for our eyes. Let's not talk about the glue that is used to do extensions in a salon. The risk of developing an eye allergy is quite high.
If you have red eyes after extensions it is likely that you are allergic to glue or the glue used is low quality. It is a fairly frequent phenomenon and every professional in the sector should inform their clients about the risks.
If you continue to have red eyes after extensions the only solution is to ask your beautician to remove them.