Dermatology Online Journal

Ant-induced alopecia: Report of 2 cases and review of the literature
Mohammadreza Mortazavi MD¹; Parvin Mansouri MD² .
Dermatology Online Journal 10 (1): 19

1. Department of Surgery,Wound Healing Research Group,University of Alberta,Edmonton,Canada 2. Department of Dermatology, Imam Khomeini Hospital , Tehran University of Medical Sciences, Tehran , Iran . mortazavir @ yahoo . com

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Abstract

Localized scalp hair loss is associated with many processes, including alopecia areata, trichotillomania, tinea capitis, and early lupus erythematosus. There are several reports of localized alopecia after tick- and flea-bites and bee stings, but there are only two reports of ant-induced alopecia in the literature. We present two cases of alopecia induced by ants of genus Pheidole ( species pallidula) and review the literature for insect-induced alopecia. Ant-induced alopecia should be considered in the differential diagnosis of localized sudden-onset alopecia, at least in some geographic areas of the world.

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Report of cases

Case 1.—A 29-year-old man living in a village at the south-east of Behshahr in Mazandaran, a northern province of Iran, was referred with the chief complaint of overnight, localized, scalp hair loss; this was noticed first as an unusual amount of hair on his pillow and bed linen upon awakening. He also reported the simultaneous presence of ants on his scalp and bed linen. Past history was negative for localized alopecia, seborrhea, or tinea capitis.

Figure 1	Figure 2
Localized hair loss of the vertex of the scalp in case 1 (Fig. 1)
Ants of the genus Pheidole species pallidula; note the large heads (Fig. 2)

Physical examination of the scalp revealed a nearly-round area of alopecia at the vertex, clinically similar to alopecia areata or trichotillomania (Fig. 1 ). The hair was cut just above the scalp surface or a few millimeters longer, mimicking trichotillomania. No erythema or scratch marks were present on the affected area. The skin and general physical examination revealed nothing significant except mild androgenetic alopecia (grade III). The collected ants were sent to the Insect Toxonomy Department of Iranian Plant Diseases Research Institute in Tehran. The ants were brownish-red, 3-4 mm in length, and some had relatively large heads (Fig. 2); They were identified as Pheidole pallidula (Nylander 1849).

The patient had normal regrowth of hair without therapeutic intervention within a few months.

Case 2.—About 1 month after observation of the first case , a 25-year-old woman living in Galugah, a small town at the east of Behshahr, was referred with a similar complaint. She was unfamiliar and unrelated to the first case. The localized hair loss occurred overnight and there were ants present on her scalp and pillow upon awakening. The only significant finding in her past medical history was mild seborrheic dermatitis.

Figure 3
Localized hair loss of the vertical area in case 2.

Physical examination of her scalp revealed a relatively large, linear area of hair loss at the vertex. The hairs were cut few millimeters above the scalp similar to the first case (Fig. 3)

The collected ants, which had similar appearance to those of the first case, were sent to the same center in Tehran. These ants were also identified as Pheidole pallidula.

The hair regrew without any medication.

Discussion

There are many different causes of localized scalp hair loss. However, as far as we know , this is the second report of alopecia induced by ants after Radmanesh and Mousavipour [1], and Shamsadini [2]; both reported their cases from south of Iran. Radmanesh and Mousavipour described sixteen cases of scalp hair loss induced by Pheidole ants in 1999 [1]. All of their cases were referred with complaint of acute, localized hair loss detected first as an unusual mass of hair seen over their pillow or bed linen upon awakening. The hair was cut just above the scalp or a few millimeter longer. Mild erythema and signs of excoriation were seen in some cases [1, 2].

Shamsadini reported two other cases of Pheidole ant-induced alopecia of scalp with similar clinical presentations [2]. Both of his reported cases complained of mild to moderate pruritus at the site of hair loss.

Tick and flea bites have been reported to be associated with patches of hair loss that could be confused with alopecia areata [3, 4, 5]. The mild inflammatory response to the tick bite inadvertently affects hair growth. The alopecia is temporary and the hair regrows when the inflammation subsides [3, 4]. Sharma et al. reported diffuse hair loss following multiple honeybee stings [6]. However, in the cases of previous [1, 2] and present reports, which the ants of the genus Pheidole were suspected as the cause of alopecia, bite or obvious inflammation of the skin is not evident and mild erythema and signs of scratching is seen only in few patients [1, 2].

Pheidole is the second largest genus of ants in the world with more than 900 species and subspecies. They are found worldwide, but are particularly abundant in the tropics and subtropics [7]. The worker caste of these ants is dimorphic. The major workers or "soldiers" have total body lengths of 2.5-6 mm and relatively very large heads. The minor workers are 2-4 mm long with unexceptional heads. In soldiers, the anteroventral margin of the cranium carries one or two pairs of small gular denticles and a median projection [7]. Division of labor is well-marked between the worker subcastes. The soldiers mainly dissect large food items within and outside the nest, and defend the colony and its surrounds [8]. In some species, the crops of soldiers are utilized for food storage [9]. Foraging workers collect honeydew from aphids and honey from flowers for adults, and solid food such as seeds and insects for the larvae [8]. In the tropics, most foraging takes place during the late afternoon and throughout the night; in the cooler regions foraging occurs at all times of the day and night [10, 11].

The major food source and also the instinctual aggressive or non-invasive behaviors are different in various species of the genus Pheidole and are probably influenced by geographical and climatic conditions [10, 11, 12].

The ants that were isolated from the scalp or bed linen of cases in all reported observations (ours and Radmanesh and Shamsadini reports [1, 2] ) were worker ants of the genus Pheidole (predominantly major ones or soldiers). Their species in our observation was pallidula, but unfortunately in both Radmanesh and Shamsadini reports the species was not mentioned or determined [1, 2].

To establish the diagnosis of ant-induced alopecia, other conditions associated with localized hair loss should be ruled out, including alopecia areata, tinea capitis, and trichotillomania. In alopecia areata, the presence of exclamation-point hairs (i.e., hairs tapered near proximal end) is pathognomonic, although it is not always found. The pull test at the periphery of the round-to-oval denuded patches of alopecia usually is positive as an indication of disease activity.

The diagnosis of tinea capitis is suggested by erythema, scaling and crusting locally on the scalp lesions. These signs were not evident in our cases. In trichotillomania, alopecia patches have unusual shapes and sizes and show broken hairs with different sizes and growing hairs in different stages of growth.

In our patients, the sudden overnight onset of hair loss, the lack of scaling and crusting, the single episode of its occurrence, the negative past history of alopecia; and the presence of ants over the scalp and among the hairs and on the pillow and bed linen on awakening, excludes alopecia areata, trichotillomania, and tinea capitis.

There was no significant medical or dermatologic disorder other than mild androgenetic alopecia in the first case and mild seborrhea in the second one.

It is not clear how these ants detach the hair from the scalp and why they show such an invasive behavior. It could be done by mechanical sawing activity of their powerful mandibles or by release of a dissolving chemical substance followed by mechanical cutting [1, 2]. It is not surprising that such small creatures, which successfully dissect much harder food particles, are able to cut hair; their purpose (nutrition, nest-making) remains an enigma to be answered by entomologic research.

We conclude that ant-induced alopecia should be considered in the differential diagnosis of localized hair loss at least in some climatic and geographic areas of the world.

Acknowledgments: We are grateful to Mrs. Helen Aalipanah, the specialist of Insect Toxonomy Research Department of Iranian Plant Diseases Research Institute , for her help in the detection of genus and species of the ants. We thank Mr. Yahya Abtali,the specialist of Mazandaran Agricultural Research Administration for his help in collecting and transfer of the specimens.

References

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