Erythema Migrans

Erythema Migrans (bulls eye rash) is a rash that is commonly associated to Lyme disease. It is most often (but not always) seen in the early stages of Lyme disease and is usually painless. Erythema Migrans can appear anywhere from one day to one month following a tick bite.

A rash occurs generally because of an allergic reaction. In the case of Erythema Migrans the rash appears because of an actual skin infection with the Lyme disease bacteria (Borrelia burgodferi sensu lato). There is no other disease that can cause Erythema Migrans and if a physician has identified the rash immediate treatment of Lyme disease is necessary.

Most patients with the Erythema Migrans rash do not recall ever having being bitten by a tick. A systematic review by the Rational Clinical Examination of studies estimates that 80% of patients may have an expanding rash, erythema migrans (EM), at the site of the tick bite. (Tibbles CD, Edlow JA (2007). "Does this patient have erythema migrans?".)

Erythema Migrans generally appears with a diameter of four inches. Occasionally Erythema Migrans rash can appear with a diameter of less than four inches. Sometimes multiple Erythema Migrans rashes may occur which indicate disseminated infection.

Click here to read our Lyme Disease Testimonials