Mysterious white line along location of spay surgery 18 months later

I have an 8 year old german shepherd mix rescue named Maggie. She was spayed over 18 months ago when taken in by Dallas Animal Services. As of 6 weeks ago the area looked perfectly clean and healthy. I cleaned the area anyway with a soft wash rag and boom, this white line appeared which I can't get to go away. 12 days ago Vet started her on Simplicef 200mg which was given for about a week. I also clean the area with DouxoS3 containing Chlorhexedine, let it dry, then apply Mupirocin Ointment 2% once or twice daily. Not seeing any real improvement or worsening. Any thoughts?

Hello - I'm afraid that I do not recognise this line on the wound and wondered whether it was a closure technique employed by your vet (like sutures) that I simply hadn't seen before.  It is a stark and major change.  It strikes me as very unusual for a vet to see a post op complication like that and make no effort to name it - perhaps they know what it is and were concerned only by the infection?  Or perhaps they are as puzzled as me and, given that it has not gone away, they are expecting to review the case soon in clinic with a view to reaching a diagnosis?   Perhaps a phone call ASAP to be triaged for a follow up appointment may shed more light on this situation.

Using Chlorhexidine and Mupirocin is the right approach, but continuous use can dry out the skin and slow recovery, especially in areas that have healed long ago. It might be worth considering reducing the That's Not My Neighbor frequency of cleansing and asking your doctor about moisturizing or skin regeneration instead of focusing solely on antibacterial treatment.