We get calls every spring from people asking about a circular red rash on their dog’s belly. People often worry this is a deer tick bite or ringworm. This red circle seen in dogs is usually caused by black fly bites. The red area is the body’s allergic response to the fly’s saliva injected when they bite. Black flies are most active during daylight hours.  They are active in the early morning and evening right after sunset.  The black fly rash does not cause any ill effects to most dogs and will go away over time. If your dog is itchy from the bites there are some topical flea and tick products that have repellent properties to them. There are also some natural spray on insect repellents made for pets that can be applied. Ask your veterinarian if one of these products would be helpful for your dog.