Can hair grow back after 1 session of laser hair removal?

Absolutely, and that should be expected. It is highly unlikely that the hair in the specific treated area only has one growth cycle. In fact, most areas have several. That’s why patients should expect to need between 6-12 treatments and then occasional touch up treatments.

Since hair grows in cycles, you will need more than one treatment for a dramatic result.  You may have some but not likely much hair reduction.  Sorry you regret your decision.  Stay skintastic 

Thank you for your question.
It is disappointing to hear that you regret getting laser hair reduction treatment.  Six sessions is minimum in order to achieve 75-85% of hair reduction.  So not to worry.   Your hair will regrow.  It might appear slightly thinner than before.  
Best,
Dr. Oleg Vinson 

Laser hair removal is permanent, but is only effective in treating the hair follicles in the growth phase. That may be only 5% of the total follicles.  So the answer is, some of the hair is likely permanently gone, but most will return.