Tick Bite Alopecia: A Report of Five Cases and Review of the Literature Free

Alopecia of the scalp after a tick bite was first described by Sauphar in 1921 [1]. Although this condition is known, not more than 15 cases have been reported in the international literature [2‒10]. We present 5 cases of tick bite alopecia of the scalp and a review of the literature.

In the period 1987-2023, we observed 5 cases of alopecia of the scalp caused by tick bites. All patients were Caucasians, 2 males and 3 females, with an age ranging from 4 to 9 years (mean age: 6.3 years). Before the tick bite, all patients were in good general health and were not in therapy with systemic drugs. Alopecia was located in all patients at the vertex of the scalp and was characterized by a single, roundish lesion with a diameter of 0.5–1.5 cm. The surface was slightly erythematous and scaly in 3 patients and smooth in 2 patients. Fragments or the entire body of Ixodae sp. were detected in 4 patients (Fig. 1). In one patient, a small crust was observed at the center of alopecia (Fig. 2). Two patients complained of mild pain. Pull test was positive in all patients at the borders of the lesions. Trichoscopy was carried out in the last 2 patients, observed in 2022 and 2023, respectively; it revealed, at the borders of the lesions, both exclamation mark hairs and black dots. Four to 6 weeks later, the number of black dots significantly decreased; they were more or less completely replaced by gray dots. Laboratory examinations were within normal ranges. Anti-Borrelia burgdorferi antibodies were negative. Neither topical nor systemic therapy was prescribed. Complete regrowth was observed 6–8 weeks after the first examination.

Tick bite alopecia of the scalp occurs in children of both genders [2‒4, 6, 9, 10]: only 2 adult patients were reported [7, 8]. Ticks responsible for alopecia were often classified as Ixodae sp.: Dermacentor sp. [5], Dermacentor variabilis [2], Rhipicephalus evertsi [4], Rhipicephalus sanguineus [4], and Haemaphysalis leachi [4]. As previously mentioned, also in our patients, Ixodae sp. were collected. Except for four patients in whom laboratory tests were positive for Rickettsia slovaca infection [5], no other cases of transmission of Borrelia sp. or Rickettsia sp. were reported in the literature. Tick bite alopecia of the scalp is characterized clinically by a single roundish or oval lesion. Total alopecia is extremely rare [10]. In the context of alopecic lesions, erythema [6, 7, 9], scaling [3, 6, 9], crusts [3], ulcers [4], and eschars [8] have been observed. Patients may complain of pruritus [2, 8] or pain [4, 9]. Exclamation mark hairs were observed by some authors [4, 6], but not by others [3, 9]. Also, telogen hairs were observed by some authors [4, 6], but not by others [3]. Regrowth occurs 2 weeks-2 months later, no therapy is usually necessary. Final clinical result may be a mildly atrophic scar [3, 4]. Permanent hair loss was reported in only 1 case [2]. Tick bite alopecia has been considered clinically similar to alopecia of secondary syphilis [2] and alopecia areata [6]. According to the results of trichoscopy, alopecia caused by a tick bite seems to be similar to alopecia areata for the presence, at the borders of the lesions, of both exclamation mark hairs and black dots. The latter are subsequently replaced by gray dots. Histopathological picture is characterized by a perifollicular lymphocytic infiltrate with numerous eosinophils [6‒8]. The mechanisms by which ticks cause alopecia are unknown. The saliva of ticks contains anticoagulants (heparins, heparinoids, and coumarins) [3, 11]. The release of these anticoagulants would induce an inflammatory reaction on the scalp, with alopecia as the final clinical result. Moreover, alopecia caused by heparins, heparinoids, and coumarins is not a rare side effect of these drugs [3, 12‒14]. The fact that ticks can be responsible for this kind of alopecia is also demonstrated by the occurrence of alopecia in moose, in particular by Dermacentor albipictus [15]. Furthermore, other athropods, such as the ant Pheidole pallidula [16, 17] and the honeybee [18], can cause alopecia, although with different mechanisms; in alopecia caused by P. pallidula, hairs are “cut” just above the scalp surface.

Some important questions about tick bite alopecia remain unanswered. In 1982, Heyl was wondering why this alopecia is so rare while tick bites are so common [4]. It is possible that tick bites on the scalp are underestimated because they may be asymptomatic. Furthermore, why is it almost exclusively in children? because of the lower thickness of the epidermis? and why has tick bite alopecia of the limbs, although they are hairy, never been reported? Unfortunately, we currently have no answers to these questions.

Written informed consent was obtained from patients’ parents for the publication of these cases including clinical images. Ethical approval was not required for this work in accordance with local guidelines.

The authors have no conflicts of interest to declare.

No funding was obtained for this work.

The content of this manuscript has not been submitted for publication elsewhere. Stefano Veraldi visited and followed the patients and wrote the manuscript. Giulia Murgia and Gianluca Nazzaro reviewed the literature. Mauro Barbareschi performed the trichoscopy. All authors are in agreement with the content of this paper.

Data are not publicly available due to ethical reasons. Further inquiries can be directed to the corresponding author.