Lyme borreliosis is the most common tick-borne bacterial infection in the temperate zone, caused by spirochetes belonging to the Borrelia burgdorferi sensu lato complex. The disease is primarily transmitted by ticks of the genus Ixodes. The classic clinical presentation includes erythema migrans, neurological symptoms, arthritis and cardiac involvement; however, the clinical spectrum is much broader than this. Due to the complex nature of the immune response that develops during infection, some patients may experience symptoms reminiscent of allergic diseases. These may include skin symptoms, hypersensitivity reactions, and certain immunological phenomena that show parallels with the mechanisms of allergic inflammation.
Allergy-like symptoms in Lyme disease may result from several different mechanisms. On the one hand, the tick bite itself can trigger a local hypersensitivity reaction; on the other hand, the immunological processes developing during the infection may also lead to reactions that appear clinically to be of an allergic nature. Furthermore, some studies suggest that Borrelia infection may influence the regulation of the immune system, which in certain cases can lead to the development of heightened hypersensitivity reactions.
Hypersensitivity reactions following a tick bite
The first step in the development of Lyme disease is the bite of an infected tick. Tick saliva contains numerous biologically active proteins and enzymes that serve to modulate the immune response. These molecules are capable of reducing the inflammatory response, inhibiting the function of immune cells, and facilitating prolonged blood feeding by the tick.
The skin reactions that often develop at the bite site – erythema, itching, swelling – are partly the result of hypersensitivity processes. The proteins in tick saliva can act as antigens and trigger the body’s immune response. A more pronounced reaction is particularly observed in individuals who have previously experienced a tick bite, as this can lead to the development of immunological memory against certain components of tick saliva.
Skin symptoms are particularly important from a differential diagnostic perspective, as the early skin symptom of Lyme disease, erythema migrans, is often confused with allergic skin reactions or a hypersensitivity response to an insect bite. The pattern of spreading redness, a history of a bite, and the temporal course of the condition can help distinguish between the two.
Immunological changes during infection
During infection with Borrelia burgdorferi, the immune system activates several different defence mechanisms. In addition to the innate immune response, the adaptive immune system also plays a significant role, particularly through the activity of T and B cells.
Numerous studies have shown that Borrelia lipoproteins are capable of activating immune cells, primarily via Toll-like receptors. This process triggers the production of cytokines and chemokines, which contribute to the development of the inflammatory response. Among the cytokines, interleukin-6, interleukin-8 and tumour necrosis factor-alpha play a particular role in maintaining inflammatory processes.
This type of immune response activation can, in certain cases, cause symptoms reminiscent of allergic reactions, such as redness, swelling or itching. However, these are not classic allergic reactions, but rather the consequences of inflammatory mechanisms triggered by the infection.
Skin symptoms and allergy-like reactions
One of the most common manifestations of Lyme disease is skin involvement. In addition to erythema migrans, other dermatological symptoms may occur, such as diffuse erythema, itchy rashes or, in rarer cases, urticaria-like lesions.
Urticaria-like reactions are of particular interest from an immunological perspective. In these cases, the oedema and erythema developing in the skin are the result of increased permeability of small blood vessels. Although classic urticaria is generally associated with an allergic mechanism, infections – including bacterial infections – can also trigger it. Several studies have reported that infectious-induced immune activation may underlie chronic urticaria.
The dermatological presentation of Lyme disease may therefore mimic allergic skin conditions in certain cases, which can pose a diagnostic challenge. This is particularly the case if the patient cannot recall a tick bite, or if erythema migrans presents in an atypical form.
Antibiotics and allergic reactions
The treatment of Lyme disease is primarily based on antibiotic therapy, which is generally well tolerated; however, allergic reactions may occur in certain cases.
Hypersensitivity reactions triggered by antibiotics can be clinically very varied: skin rash, itching, urticaria, and, more rarely, more severe reactions may occur. For this reason, it is important to consider the possibility of a drug allergy during the treatment of Lyme disease.
In clinical practice, it may also happen that skin symptoms developing during the infection are attributed by the patient or the doctor to an antibiotic allergy. Therefore, careful assessment of the timing of symptom onset and their relationship to treatment is necessary.
Cross-reactions and immunological sensitivity
One important aspect of the link between infectious diseases and allergic reactions is the cross-reactivity of the immune system. Certain bacterial antigens may be structurally similar to other environmental antigens, which can result in cross-reactions during the immune response.
In Lyme disease, for example, it has been observed that certain bacterial antigens may cross-react with proteins from other microorganisms. Theoretically, this could also contribute to the development of certain hypersensitivity phenomena.
This type of activation of the immune system may be particularly significant in cases where the infection persists for a prolonged period or where the body’s immune response remains in a persistently activated state.
Patient reports and clinical observations
In clinical practice, many patients report experiencing newly developed sensitivities or allergy-like symptoms during Lyme disease. These may include intolerance to certain foods, skin reactions or respiratory symptoms.
Based on patient reports and clinical experience, these phenomena are not uncommon, although their exact pathomechanisms are not always known. In some cases, it is likely that the immune activation occurring during the infection may contribute to increased reactivity of the immune system.
Summary
Lyme borreliosis is primarily an infectious disease; however, due to complex reactions of the immune system, allergy-like symptoms may also appear in the clinical picture. The development of these symptoms may be influenced by a hypersensitivity reaction to the tick bite, the inflammatory immune response that develops during the infection, and, in certain cases, antibiotic therapy.
Recognising and properly assessing allergy-like symptoms is important during the diagnostic process, as these can easily mislead the clinician. Future research is expected to further clarify the link between the infection and allergic phenomena, which may contribute to a deeper understanding of the pathomechanism of Lyme disease.
Sources:
https://pubmed.ncbi.nlm.nih.gov/27976670/
https://pubmed.ncbi.nlm.nih.gov/10024550/
(C) Lyme Borreliosis Foundation
