What is a bullseye rash? This is a skin rash caused by a type of bacterium that is not found on human skin. It is transferred to human skin from certain animals via ticks. When a tick bites and feeds on an animal that is infected with the bacteria and then subsequently ends up on a human and bites him or her, then there is the possibility of the human being infected with the bacteria. If this occurs then a bullseye skin rash can develop. This type of rash is also known as a Lyme disease rash.
Why is this type of rash called a bullseye rash? The reason is simple - the rash that appears on the skin looks like the center area of a dartboard or the bullseye area. The rash does not appear right away after the bite, but rather after a few days of being bitten by the tick carrying the bacteria. Initially, a tiny red spot is evident at the site of the bite, but this little spot eventually grows wider and in the shape of a red circular patch or slightly oval patch. After a few days the area close to the tick bite site starts to fade and therefore you have a red spot at the bite site that is surrounded by a ring of non-red skin or normal skin color and then a red ring on the outside of this area.
The affected area can spread to twelve inches in diameter and the characteristic bullseye pattern may disappear in a short amount of time. If the Lyme disease progresses a skin rash on other parts of the body may appear.
This type of skin rash can be painful, with burning and itching being the main symptoms.
The pictures of skin rashes provides additional skin rash information.
Another useful resource is the diagnose my skin rash page which provides more detailed information on Lyme disease rash and on a number of other different types of skin rashes.