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Can anyone tell me what this weird glow around enemies is?

This started appearing on enemies lately, and I have no clue what it is. It seems to be only certain enemies, I can't tell which ones yet. I turned all addons off in case it was one of those, but the effect was still there. In that screenshot, you can see it on the boss too as well as the ones on the floor.
My boyfriend is next to me and took an identical screenshot, he doesn't have this effect, and we compared all our graphic and interface settings. So is it some class ability?
Total Champion Points: 1000+
Main Character: Ithaera - Stam DK, Nord, Female, DD, Werewolf.
Rothelnog - Stam NB, Orc, Male, DD, Werewolf.
J'Xena - Mag DK, Khajiit, Female, DD, Werewolf.
Dances-With-Frost-Dragons - DK, Argonian, Male, Tank, Werewolf.
Raziel The Paradox - Mag TP, Dark Elf, Male, DD, Vampire.
Swims-Through-Starlight - TP, Argonian, Female, Healer, Werewolf.
Glaicean Mag Ward, High Elf, Male, Ice DD, Werewolf.
Hjurne Hircine's Forsaken - Sorc, Redguard, Male, PvP DD, Werewolf.
My Total Free Werewolf Bites: 400+ (Ask me about bites if you need one!)
Playing since July 2015!