Anthrenus sp. and an Uncommon Cluster of Dermatitis

We report patients in their homes in France who had cutaneous lesions caused by Anthrenus sp. larvae during the end of winter and into spring. These lesions mimic bites but are allergic reactions to larvae hairs pegged in the skin. These lesions should be distinguished from bites of bed bugs or fleas.


DISPATCHES
We report patients in their homes in France who had cutaneous lesions caused by Anthrenus sp. larvae during the end of winter and into spring. These lesions mimic bites but are allergic reactions to larvae hairs pegged in the skin. These lesions should be distinguished from bites of bed bugs or fl eas.
wool, dust, dead skin cells, feathers, and hairs; thus, they are commonly found in wardrobes, on stuffed animals, mattresses, or under carpets (6,7). Larvae never infest living animals. The larvae of many species of carpet beetles are covered with spear-headed hairs. These hairs are disseminated throughout the interior of a home by a natural air stream or an air conditioning system. We observed for 1 child from the first family a large number of lesions (35 papules), probably caused by the air conditioning unit located above her bed. Two kinds of hairs coexist on these insect larvae. One hair is fine and has a terminal arrow, and the other hair is thick and has scales ( Figure 2, panel E). Among the hairs of the Anthrenus sp. larvae, only the fine prickly hairs are responsible for lesions. Their spearheaded shape enable them to get stuck in the skin or respiratory mucosa, leading to hypersensitivity reactions in the hosts (8). Few cases of dermatitis caused by Anthrenus sp. beetles have been described (6,9,10). Even rare cases of asthma could be linked to the presence of carpet beetle larvae in the house (11).
Several steps (excluding insecticides) were recommended to quickly help the 7 families eliminate their lesions and clean their homes. All patients were given antihistamines and topical corticoids.
Clothing that had direct skin contact and was to be worn in the next few days was washed to eliminate larvae hairs and stored after drying in airtight bags to protect them from the environment. In the homes, places where Anthrenus sp. beetles were found were inspected and cleaned. Insects were removed mechanically. Mattresses and other infested areas were vacuumed, and the vacuum bag was put in a plastic bag in the trash. Air conditioning systems present in the infested rooms were cleaned to prevent larvae hairs from spreading.
After observance of the above protocol, skin lesions healed in all affected adults and children in 3 days. A month later, no other lesions were observed in the 7 families.

Conclusions
In our medical experience, infestations by Anthrenus sp. beetles have been sporadic. We observed a large number of cases during a short period, and a new case of Anthrenus sp. infestation was being investigated when this manuscript was being written. The families described in this report lived either in houses or apartments. They were not geographically near each other, but they all lived near parks or green spaces in urban or periurban areas.  Proper detection and identification of specimens is a key step in controlling insect pests. Anthrenus sp. larvae are responsible for allergic cutaneous reactions (not bites) caused by hairs hooked in the skin, leading to lesions found under clothing in members of the same household. The environment should be investigated for this carpet beetle in the case of skin lesions mimicking arthropod bites without a central blister. Reactions to larvae hairs are different from 1 family member to another, and >1 of these family members frequently have no symptoms.
Dermatitis caused by Anthrenus sp. larvae is underdiagnosed or confused with dermatitis caused by bed bugs or fleas. These erroneous diagnoses can lead to use of insecticides and thus to unnecessary, tiring, expensive, and toxic procedures. Dermatitis caused by Anthrenus sp. larvae has clinical and environmental characteristics relevant to ruling out other entomologic causes. It is useful to know that lesions caused by this insect are isolated and located mostly under clothing. Also, these insects are found in late winter or during spring, and bed bugs or fleas are not found contemporaneously. This insect pest has been uncommon in human medicine, and these cases could indicate its emergence. Physicians and dermatologists should be better aware of this insect.  ); B, C) larval stage (length 4 mm) found inside clothing and upholstery fabric; D) larvae (original magnification ×40); and E) larvae (original magnification ×200) showing fine hairs (single arrow) that have a spear-headed shape, are responsible for human hypersensitivity, and are invisible to the naked eye. Double arrow indicates thick larvae hair.