I’ve had 3 laser sessions done on my arms, and have noticed this also.
As a matter of fact, my 3rd session was over a week ago, on the 2nd.
Here’s what I’ve observed, after each laser session:
Some hairs are missed completely, and continue to grow. Even with slow, careful pulses, it’s impossible to get them all. My laser technician only zaps about half the surface area, to avoid overlapping (which causes burns). This can be annoying, because it basically doubles the number of treatments you need. I don’t know how to tell the technician nicely that they missed so many spots.
Some hairs are treated, but don’t respond for some reason, and continue to grow.
Some hairs are expelled by the skin, and although they appear to grow, after a week or more they “stop”. Your mind might play tricks on you, but if you wait a while and give these hairs a gentle tug… they will come right out. Don’t tug too hard… if the hair resists, or gives you pain when you tug it, it’s not a dead hair.
Some hairs will soon/later enter the growing phase. These new hairs could have never been treated, but should be in full production by your next session.
So… Although it’s been a week, my arms still have some hairs on them. Some are growing, some are dead and will eventually fall out. It’s a bad idea to tug them (but I do anyway) because if you get a live one… it won’t be treated in your next session.
Although I recently started my legs, and have become a little worried about the recent burns I received, my arms respond nicely. Unfortunately laser results take lots of time, so as long as you’re not burned (!), just keep going back every 2-3 months or whenever they tell you.
Hope this helps?