Is it normal to be itchy by my incisions 3 weeks post op? Looks like a rash

You should make an appointment with your plastic surgeon for an in person examination as the symptoms you are describing could indicate a number of things. More pictures would be helpful, but having your doctor examine you and prescribe further treatment is probably necessary.

Incision reactions can be used to the surgical prep solution, the stitches, the glue, tape, etc. If topicals such as Benadryl cream do not work, steroid creams might. You should visit with your plastic surgeon to get his or her recommendations.Best of luck!Dr. SubbioBoard-Certified Plastic SurgeonNewtown Square/Philadelphia, PA

"Itchiness" is frequently a byproduct of the healing process.  On a cellular level, the inflammation associated with healing can often come with the release of factors which cause that sensation.  Sometimes with an allergy, that itchiness can become more severe.  This is typically self-limited and will go away with time.  It is important to make sure the rash you are describing does not represent an infection.  In either case, the more appropriate course of action is to be evaluated by your surgeon who can guide you to the most appropriate course of action.  Good luck!