Have you heard of lash growth cycle?
Each day we lose few natural lashes, (3-5/each eye), but often they fall out unnoticed unless they fall into your eye. When we wear eyelash extensions, we are more aware they shed, cause they're longer, thicker and darker than natural lashes (easier to notice when fall out). If you sleep on your stomach with your face pressed into the pillow, or you sleep on one side mainly, you may notice the lashes may not last as long as on the other side. Having lashes done during pregnancy (rare but possible), or during period also affects retention.
Sometimes clients ask why they lost so many lashes, or complain that they fell out quicker than usual. Ask them if they noticed whether lashes have been falling out with or without natural lashes. If with a natural lash - that means - their own lashes' growth cycle is that long and no one can do anything about it. Some people lose more lashes a day than the others and that's completely natural.
If lashes fall out without natural lashes that may mean few things:
Make sure you isolate a natural lash before applying an extension. A good isolating tweezer is straight and fine pointed, like the one HERE
Remember that certain amount of glue is required to get a good glue bond. If you do classic 1:1 lashes - dip 1/3 to 1/2 of lash in a glue and wipe off an excess of glue if needed.
You can either "swipe and stick" lash extension, or put it on, press little bit, hold for a 1-2 secs and let go.
poor aftercare - client might have not looked after them as they should. Pulling, playing with lashes, using mascara, oily make-up products don't help too. Rubbing eyes, pouring water on lashes, going under water in a bath/shower, diving, using sauna or even sun bed is bad to eyelash extensions too. Give your client a leaflet about aftercare, in case they forget to what to do.
bad quality products - make sure you use greatest quality eyelash extension glue. It should be as thin/watery as possible, dry in 0.5-1 seconds ideally, have great retention and have low or no fumes at all. One of the lash adhesives that has all the features above is well known Dream Lashes Master-PRO.
natural lashes haven't been prepared before application - before an application natural lashes should be cleansed; ideally with an eyelash cleanser (pre-treatment) or saline solution and then primer. Both solutions remove dirt, dust, oil and proteins from lashes which help create stronger bond between glue and lashes. Skipping this procedure will result with short retention and unhappy client.