IPL effectiveness after 2 treatments?

Generally speaking, IPL is most effective as a series of treatments.  The biggest wow effect is if your treatments are done in a series together, however you can still see results after 2 treatments and then a short break before picking back up again.  Don't forget to use sunscreen in between treatments.  Settings with IPL procedures are everything, so if you did not notice a result after your first treatment the settings may have been not ideal for your skin type.  There are also hundreds of different IPL machines on the market.  At my practice we have the M22, the Lumenis One and the Palomar Icon.  The M22 is the current gold standard available in the marketplace.Furthermore, I would normally prefer to use photodynamic therapy, topical/oral medication and a good skincare regimen for acne.  Using IPL for post-inflammatory hyperpigmentation is reasonable. Have you tried any of these yet?  

IPL Limelight works well to reduce redness and brown spots on the face. In our office, we use it for premature aging and skin rejuvenation with excellent results. Best, Dr. Karamanoukian Los Angeles

I suggest seeing a cosmetic dermatologist with experience. IPL is not a treatment for post inflammatory hyperpigmentation and has the potential to make it worse.  Best, Dr. Emer.