The Borrelia bacteria (Borrelia burgdorferi) is transmitted through tick bites. Approximately 10-40% of ticks carry this bacterium. The risk of being bitten by ticks varies. Tick bites are most common in the summer and early fall.
In cases of Borrelia infection in the skin, a characteristic rash called erythema migrans may develop. This is a relatively harmless condition, but it should be taken seriously as it can be an early stage of Lyme disease. Lyme disease is a more severe, chronic infection caused by the Borrelia bacteria. It can affect the nervous system (such as the meninges and facial nerve), eyes, heart, and joints. The risk of developing Lyme disease after a tick bite is approximately 0.5-2%.
Tick bites are usually painless due to the anti-inflammatory and analgesic substances in tick saliva. The tick bite itself can cause a reddened swelling of the skin, similar to other insect bites, which typically resolves within a couple of days.
Erythema migrans typically appears one to two weeks after the tick bite. The rash is characterized by a gradually expanding red ring, often with a fading center. Erythema migrans usually exceeds 5 cm in size (often around 15 cm) and grows by 2-3 cm per day.
Common locations for tick bites and erythema migrans are areas of thin skin, such as ankles, knee creases, groin, and armpits. However, tick bites can occur almost anywhere on the body. In children, ticks are often found in the scalp/hairline and behind the ears.
The diagnosis of erythema migrans is usually based on the patient's medical history (known tick bite, residence in a high-risk area, etc.), along with the appearance and progression of the rash. Only about one-third of patients with erythema migrans are aware of the tick bite. Erythema migrans typically does not cause significant symptoms, but some individuals may experience mild itch or warmth in the affected area. In rare cases, flu-like symptoms such as malaise, muscle/joint pain, headache, and enlarged lymph nodes near the bite site may occur. Fever is not common.
If there is uncertainty about the diagnosis, blood tests can be performed to assess antibody levels. In rare cases, a skin biopsy may be recommended to rule out other possible causes.
Erythema migrans is caused by the Borrelia bacteria (Borrelia burgdorferi), which is transmitted through tick bites. It has been documented that the risk of bacterial transmission increases the longer the tick has been attached to the skin. Usually, the tick needs to be attached for at least 24 hours for transmission to occur.
Ticks should be removed from the skin as soon as possible. Early removal can prevent transmission of Borrelia. However, if erythema migrans develops, this condition is treated with antibiotic tablets for approximately one and a half weeks. Antibiotic treatment is curative, as it causes the rash to disappear and prevents Lyme disease. In cases of Lyme disease, especially in advanced stages, not all symptoms may disappear despite antibiotic treatment.
It is therefore important to seek medical help as early as possible. If antibiotic treatment is not received for erythema migrans, the rash usually resolves on its own within 3-4 weeks. However, there is still a risk of Lyme disease if the bacteria spread to other organs.
It is not routine to provide (preventive) antibiotic treatment for tick bites alone without evidence of erythema migrans or other symptoms related to Borrelia.
Other skin infections, such as ringworm/tinea (superficial fungal infection), erysipelas/cellulitis (superficial bacterial infections), and cellulitis (deep bacterial infection), may partially resemble erythema migrans. Urticaria/hives, which typically move within 24 hours, can also occasionally resemble it.
The most important preventive measure against tick bites and erythema migrans is to cover exposed skin when in tick-infested areas. The insect repellent DEET, the most common active ingredient in mosquito repellents, can also provide some degree of protection against tick bites. It is recommended to inspect the skin daily, preferably with the help of another person or using a mirror, when staying in tick-infested areas. Remove attached ticks as quickly as possible. There are instructional videos available on the internet that can be helpful. Cleansing the bite site with soap and water is recommended.
