Ticks feed on your dog's blood by digging their heads into the skin and gorging on blood. Naturally, it's an unpleasant experience for your pooch. Even after the tick has been removed, it can leave a mark on your pet's skin where he attached himself. If the tick was decapitated during removal and the head remains in the skin, or if the bite gets infected, it can become even more red.
Tick Bite Aftercare
Removing a tick stubbornly attached to your dog may result in an accidental beheading, the head remaining buried under your pet's skin. If this happens, the wound can fester, turning red and swelling. If you decapitate the tick during removal, make an appointment to see your veterinarian to make sure your dog doesn't experience complications. Otherwise, just keep the site of the bite clean for a few days by gently cleaning it with alcohol and canine antibacterial ointment -- consult your vet first, as he can recommend how often and with what technique to do so. If you don't keep it clean, it can get infected and turn a more distinct shade of red and swelling.