Acne scars are deep. Any machine used to improve the scars will have some downtime. Most lasers or other machines will cause some redness for 2 to 3 days followed by scabbing or crusting in some which takes another 3-4 days minimum to heal. Recovery period will vary from person to person depending on skin type. Side effects can occur if the patient does not strictly follow the aftercare advised by the concerned doctor, common being pigmentation.