Unfortunately not everyone can wear lash extensions. No matter how much they'd love to have them, there are some factors that could cause harmful consequences of having eyelash extensions.
Eyelash technician needs to advice their clients to check if they're not contraindicated to receive a treatment. The therapist can not be held responsible if something goes wrong, as it is assumed the clients have checked they do not suffer from any of the listed contraindications prior to booking an appointment. Some of the contraindications below are related to diseases, and some are just general reasons why a person should not have lash extensions (as they may not last or be falling out prematurely).
Reaction to patch test (which should be performed at least 24h prior a treatment. If eyes get swollen, puffy, watery, or red it may indicate glue reaction)
Any contagious skin conditions on or around the eyes or eyelids.
laser eye surgery - at least 4 months gap should be left due to oversensitive eyes and possible medications client is on.
Eyelash perming - at least 3 months gap should be left, otherwise lashes may not last as long
chemotherapy - at least 6 months gap should be left, otherwise lashes may not as long due to a number of medications that can affect lashes or eyes
Eye injuries/bruising (wait until it's healed completely)
Diseases such as: madarosis (lack of eyelashes), blepharitis, distichiasis, trichiasis, trichotillomania, alopecia (treatment can not be done as client's lashes are not suitable for lashing, or there are no or not enough lashes to have them extended)
If they are the "eye rubbers" due to allergies, such as hay fever or if rubbing their eyes is just a habit, or in the past they have experienced sensitivity around the eye area after using skin care or makeup, or generally having sensitivity around that area – it might not be for them
If they use prescribed medicated eye drops or ointment - this may coat the lashes and cause them to clump, making them coming off quicker than expected
Be strict and consistent. You should not proceed with a treatment if your client admits that they have any of the conditions above. If they insist - say "no" and explain that your insurance policy doesn't allow you to do a treatment. Otherwise - if anything happens - you won't be covered by your insurance, even if they sign any type of disclaimer.