Scabies: A Thorough Review and Treatment Update

Review Article

J Fam Med. 2019; 6(6): 1185.

Scabies: A Thorough Review and Treatment Update

Duff DB1*, Desrosiers AS1, Brodell RT2 and Helms SE2

¹University of Mississippi School of Medicine, USA

²Department of Dermatology, University of Mississippi Medical Center, USA

*Corresponding author: Duff DB, University of Mississippi School of Medicine, 720 Gillespie Street Jackson, MS, USA

Received: September 10, 2019; Accepted: November 01, 2019; Published: November 08, 2019 2019


Primary care physicians manage a large portion of skin-related encounters, and scabies is an exceptionally common disease of the skin. It is highly likely that primary care physicians will encounter a patient with scabies in their clinic. For this reason, we provide a review of the scabies mite, the clinical presentation of human infestation, and the methods available for diagnosis and treatment of the disease.

pKeywords: Scabies; Sarcoptes Scabiei; Crusted Scabies; ; Permethrin


One in three Americans are affected by skin disease at any given time [1]. Approximately half of skin complaints (52.9%) are initially evaluated by non-dermatologist providers. Family medicine practitioners manage 20.5% of all skin-related encounters, and 6.0- 8.0% of all outpatient visits for primary care physicians are skin complaints [1-3]. With an estimated prevalence of 200 million individuals worldwide, scabies is an exceptionally common skin disease [4]. Thus, it is vital for primary care physicians to be able to effectively diagnose and treat the condition. In our review, we discuss the scabies mite, the clinical presentation of human infestation, and the methods available for diagnosis and treatment of the disease.

The scabies mite: Scabies, caused by the mite Sarcoptes scabiei var. hominis, has plagued humanity for thousands of years and continues to do so despite the development of effective pharmacologic interventions [5,6]. The scabies mite is an unbiased pestilence that afflicts both men and women regardless of age, ethnicity, or socioeconomic status [7,8]. As obligate parasites, the mites undergo their entire life cycle on their human hosts [9]. They burrow into the skin at the level of the stratum corneum to feed on human tissue and deposit their eggs [9,10]. An allergic reaction occurs as the human immune system encounters components of the mite’s saliva, eggs, and feces [11]. This hypersensitivity reaction creates the classic clinical presentation of severe, generalized pruritus with a nocturnal predominance [12].

The scabies mite has a round, translucent body with protruding jaws and four pairs of brown legs [8,13]. The female mite, barely visible to the human eye at 0.3x0.5mm, is larger than the male [5]. All scabies mites require a host for survival. Once the mite inhabits a new host, it crawls along the skin before flattening its body to initiate penetration [14]. Using proteolytic secretions, the mite dissolves and consumes tissue to propel itself forward at a rate of 0.5 to 5.0 mm per day just beneath the stratum corneum [9,14]. As it tunnels, the mite creates a serpiginous burrow in the stratum corneum that is pathognomonic for the diagnosis of scabies. Unfortunately for clinicians, these burrows are rarely visible to the naked eye unless they are surrounded by significant inflammation or darkened by components of the mite or its waste [10].

The life of a female mite spans roughly four to six weeks [9]. Within hours of penetrating her host, the female lays her eggs at a rate of 2-4 eggs per day [9,13]. Two to four days later, her larvae hatch and move along the surface of the skin until they seek shelter and sustenance by burrowing into the skin in new areas [9,13]. Ten to fourteen days after hatching, the larvae develop into adult mites [5]. The adult mites are capable of surviving and remaining infective in isolation for 24 to 36 hours at standard room conditions (21°C and 40 to 80% relative humidity) before succumbing to desiccation [14]. In order to inhabit a new host, the mite must crawl to its victim attracted by both heat and odor as guiding stimuli [15].

Scabies is primarily transmitted by direct skin-to-skin contact through contact with infested individuals. It is commonly spread to sexual partners and throughout families or friends living in close proximity. Individuals attending or residing in institutional settings such as schools, prisons, and nursing homes are most commonly exposed, as close contact is unavoidable [5,6,16,17]. Since scabies mites can survive and remain infective for up to 36 hours, fomites can play a role in indirect transmission [14,15]. These fomites include bedding, clothing, furniture, and carpeting, albeit they play a much smaller role than direct contact with a host [6,18].

Clinical Presentation

Scabies patients classically report widespread, intense pruritus especially at night. They may also have a history of immunosuppression, residency in an institutional setting, or close contact with another pruritic individual [8,19]. Patients may be infested for up to 4-8 weeks before mounting an inflammatory response to mite antigens. This response leads to itching, and many patients are pruritic for an extended period of time before the appearance of skin lesions [13,20]. In subsequent infestations, the host is already sensitized, and symptoms may appear within one to two days [13].

When they appear, common primary lesions include papules, vesicles, pustules, and nodules [17] (Figure 1). Non-specific secondary lesions including excoriations (Figure 2), eczematous eruptions, and secondary bacterial infections (e.g. impetigo due to Streptococcus or Staphylococcus) are also commonly seen [5,11,16,17].