Advantage Multi turned Gator's fur black

[GatorRay]

I posted on another site that it was K9 Advantix but it wasn't, it was the Advantage multi. Anyway, I put it on him and it turned the fur at the application site BLACK. Most of it came off with a baby wipe but it was really strange.  The vet said she had never heard of that before. Anyone had that happen or want to take a guess as to what that was?? I checked the Advantage website and I don't see anything about that.  We are switching him to trifexis for next time but I am nervous that it is the kind they ingest. 

[mtc]

All I can think of is a chemical reaction to any soap residue in his fur.

The black came off - not the fur - right?

I use Advantix on Meaty - actually it's time to re up it - I go down a weight size over Winter and then up it to his weight during warmer weather.

[GatorRay]

Soap residue could be it. I gave him a bath the night before so that I didn't need to bathe him again until a week later.  Didn't want to chance washing any of it off.  The fur was fine other than being black. lol.  It still has a greyish tinge and he has had a bath since then.

[winwinsmom]

JMHO and what I was always told is that you should wait 48 hours after bathing to apply advantage or 48 before.  Unless you are using a non-detergent shampoo.
Hope this helps.