What Might Cause a Skin Rash Following Vaser Liposuction?

Hi, it is hard to assess without photos and without detailed information, such as how far you are with your recovery or when did you first notice the rash. There are a number of factors that can contribute including #medication, #garment or #bruising. 
It is best to discuss with your surgeon other options for compression garment or if you are allowed to put topical medication for the rash. You may also ask if there's a need to change your aftercare medications. Also, if you are in your early days of recovery, redness is usually the beginning of a bruise and will progress to blue, purple, and finally to healing stage of green and yellow.
Follow the instructions provided by your plastic surgeon when moving forward through the healing process and make sure you get plenty of rest and treat the incisions well. I hope your concern was addressed. 
#RealSelf100

Skin rashes are often due to the garment or topical medication.  Many topicals contain sulfa and this causes rashes for many people.

Without pictures and a more detailed description of your rash  your question is difficult to answer. However, post surgical rash can be caused by a number of factors 1) drug reaction: intraoperative antibiotics, anesthetics, pain medications, post op antibiotics etc 2) contact dermatitis from compression garments, steristrips etc.  So, please call your plastic surgeon and describe the rash if you  are having breathing issues, go to the emergency room. Best of luck Dr. Renucci