Eyelash extensions are designed to make people look like they have fuller lashes without mascara. It’s best to have a professional apply them to avoid irritating your eyes and so they’ll look more natural.
Some people stand an increased risk of problems from the start because the length or thickness of their real lashes might not be compatible with having extensions attached to them.
When applying the upper lashes, the lower ones have to be covered properly while the glue dries (and vice versa) so the lashes don’t accidentally bond together.
You can have an allergic reaction to the adhesive used to hold the lashes in place, which can be painful or uncomfortable.
Candidates have complained that eyelashes that came out when the extensions were applied didn’t grow back at all after the extensions came out.
Having the lashes applied or removed can damage your real ones by breaking them off or turning them brittle.
Keeping the lashes looking nice requires they be carefully washed and dried, and they need to be replaced about every 6 or 8 weeks, so you need to invest time in maintaining them.
References and ResourcesAmericanChronicle.com: Fake Eyelash Extensions - The Pros and Cons
PlastiSurgeryPractice.com: The Eyelash-Extension Risk
ExtendYourLashes.com: Conditions of Use