What’s Eating You? Chiggers
Belonging to the Trombiculidae family of mites, chigger specifically refers to the larval stage of the mite’s life cycle when it is able to bite its host. Although humans act as an accidental host, chiggers will latch on to the skin and their feeding process leads to localized inflammation and irritation. In most cases, these pruritic erythematous papules and papulovesicles are self-healing within a couple weeks, so only symptomatic relief is required as necessary by means of topical antipruritics, oral antihistamines, topical corticosteroids, or an intralesional triamcinolone acetonide injection in severe instances. The best practice, however, is to take preventative measures by completely covering one’s skin and applying products containing DEET to the skin and clothing when traveling in infested areas.
Practice Points
- The classic clinical presentation of chigger bites includes severe pruritus, cutaneous swelling, and erythematous papules and papulovesicles appearing in groups, most commonly affecting the legs and waistline.
- Because itching generally subsides within 72 hours of the chigger bite and cutaneous lesions typically heal within 1 to 2 weeks, treatment is focused on symptomatic relief.
- Symptomatic relief may be achieved by means of topical antipruritics or oral antihistamines as well as potent topical corticosteroids or an intralesional triamcinolone acetonide injection in severe cases.
Disease Management
Because the lesions are self-healing, treatment is focused on symptomatic relief of itching by means of topical antipruritics (eg, camphor and menthol, pramoxine lotion) or oral antihistamines (eg, diphenhydramine, hydroxyzine). Potent topical corticosteroids may be used to alleviate inflammation and pruritus, especially when occluded under plastic wrap to increase absorption. In severe cases, an intralesional triamcinolone acetonide (2.5–5 mg/mL) injection may be required.9 The best practice, however, is to take preventative measures to avoid becoming a host for the mites. Patients should take special care when traveling in infested areas by completely covering their skin, tucking pant cuffs into their socks, and applying products containing DEET (N,N-diethyl-meta-toluamide or N,N-diethyl-3-methylbenzamide) to the skin and clothing. The odds of prevention are increased even further when clothing also is treated with permethrin.11
In parts of Asia and Australia, these mites may transmit Orientia tsutsugamushi, the organism responsible for scrub typhus, through their saliva during a bite.12 Scrub typhus is associated with an eschar, as well as fever, intense headache, and diffuse myalgia. It responds well to treatment with doxycycline 100 mg twice daily.13 Studies investigating genetic material found in trombiculid mites across the globe have detected Ehrlichia-specific DNA in Spain,14Borrelia-specific DNA in the Czech Republic,15,16 and Hantavirus-specific RNA in Texas.17 There is evidence that the mites play a role in maintenance of zoonotic reservoirs, while humans are infected via ingestion or inhalation of infectious rodent extreta.18
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