Hi,
Post-laser erythema is often a reflection of the depth and degree of laser-induced injury to the skin.
No post-laser erythema may suggest minimal or no laser-induced injury. While this may mean no downtime, it will probably also mean minimal clinical results.
For some lasers e.g. deep penetrating fractional CO2 lasers for the treatment of acne scars, significant post-laser erythema is expected if treatment is to yield significant results. This is because the treatment must go deep to release the old scar tissues and to stimulate new collagen formation to improve the appearance of the acne scars.
Hence, depending on the condition being treated and your tolerability for downtime including post-laser erythema, your doctor will advise on the use the most appropriate device/treatment modality and will calibrate the laser energy setting to help you achieve the desired results associated with the downtime that you are able to accept socially.
Do have a thorough discussion with your preferred aesthetic doctor your expectations and come to a common understanding before commencing your laser treatment and you should be fine.
Hope this helps!