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Skin Rashes in Children Introduction


AUTHOR AND EDITOR INFORMATION

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Author: Camila K Janniger, MD, Clinical Professor of Dermatology, Clinical Associate Professor of Pediatrics, Chief of Pediatric Dermatology, New Jersey Medical School

Camila K Janniger is a member of the following medical societies: American Academy of Dermatology

Coauthor(s): Giuseppe Micali, MD, Head, Professor, Department of Dermatology, University of Catania School of Medicine, Italy; Ulrich Hengge, MD, MBA, Professor, Department of Dermatology, Heinrich-Heine-University Düsseldorf, Germany; Mudra Kumar, MD, MBBS, MRCP, Associate Professor, Department of Pediatrics, University of South Florida College of Medicine; Jennifer R Casatelli, MD, Consulting Staff, Department of Pediatrics, Watson Clinic of Lakeland, Lakeland Regional Medical Center

Editors: Kevin P Connelly, DO, Clinical Assistant Professor, Department of Pediatrics, Division of General Pediatrics and Emergency Care, Virginia Commonwealth University; Medical Director, Paws for Health Pet Visitation Program; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School; Merrily P M Poth, MD, Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences; Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center

Author and Editor Disclosure

Synonyms and related keywords: scabies, itch mite, Sarcoptes scabiei, S scabiei, Norwegian crusted scabies, Norwegian scabies, crusted scabies, pruritus, burrows, papules, vesicles, pustules, nodular scabies


INTRODUCTION

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Background

Scabies is a common infestation in the pediatric population caused by the arthropod Sarcoptes scabiei. The mite is transmitted via prolonged direct human contact and rarely by fomites. The adult female mite is 0.3-0.5 mm long and has 4 pairs of legs. The term scabies is believed to be derived from the Latin term scabere, which means to scratch, or possibly from the term scabs, which are secondary to bacterial infection.

Pathophysiology

The skin is the main organ involved. The lesion is caused by the gravid female mite burrowing beneath the stratum corneum. She leaves behind a trail of debris, eggs, and feces (scybala), which induces an immunologic response. The female can lay as many as 90 eggs in her 30-day lifespan. The larvae hatch in 3-4 days; they mature to adult forms over the next 2 weeks and continue the cycle. The average patient is infected with 10-15 live adult female mites at any given time.

Pruritus, the main clinical manifestation, is caused by hypersensitivity to the debris, eggs, and feces, rather than by the direct effects of the mite. The primary lesions appear 3-10 days after exposure to the mite. These lesions include burrows, papules, vesicles, and pustules. The rash usually becomes intensely pruritic several days later because the immune system requires time to mount a hypersensitive response. Nocturnal pruritus is characteristic of scabies infestation. An immunologic study analyzing the cellular infiltrate types and patterns in lesions of scabies concluded that T4 cell dominance is the cause of persistent itching and T8 increase leads to improvement in the pruritus.1

Frequency

United States

Scabies may be observed in people of all ages and is not always a disease of overcrowding. Norwegian (crusted) scabies is observed in patients who are immunocompromised, HIV positive, or institutionalized.

Mortality/Morbidity

Intense pruritus is the major morbidity associated with scabies. This often leads to excoriation and secondary bacterial infection.

Race

No racial predisposition to acquiring scabies has been noted.

Age

Scabies can infect people of all age groups from infancy to adulthood.


CLINICAL

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History

  • Main presenting symptoms include rash and intense itching.
  • In young infants, pruritus may be difficult to detect. Irritability, especially during sleep, may be the only symptom.
  • A history that includes exposure to other infected family members and contacts is common and helps in establishing the diagnosis.

Physical

  • Primary and secondary lesions
    • The classic rash of scabies includes primary and secondary lesions.
    • The primary lesions include burrows, papules, vesicles, and pustules.
    • The secondary lesions occur from scratching and include excoriated papules and crusted areas.

  • Rash distribution
    • In infants, the most commonly affected areas are the palms, soles, axillae, and scalp.
    • Involvement of the face is uncommon in people older than 5 years.
    • In older children and adults, lesions are usually confined below the neck and involve the web spaces between the fingers, flexor surfaces of the arms, wrists, axillae, and the waistline. The umbilicus, nipples, penis, and scrotum may also be affected.
  • Norwegian (crusted) scabies
    • Norwegian scabies is characterized by crusted lesions and scaly plaques located mainly on the hands, feet, scalp, and other pressure-bearing areas. These may sometimes generalize. Hyperkeratosis may occur in these lesions.
    • Patients with Norwegian scabies can be infected with hundreds to millions of adult female mites. As a result, this type of scabies is highly contagious and may spread rapidly through patients in an institutionalized setting.

  • Nodular scabies: Orange-red nodules located in the axillae and groin define nodular scabies. These nodules are pathognomonic of scabies infection.

Causes

See Pathophysiology.


DIFFERENTIALS

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Atopic Dermatitis
Contact Dermatitis
Gianotti-Crosti Syndrome
Urticaria

Other Problems to be Considered

Canine scabies
Dermatitis herpetiformis
Drug reactions
Insect bites
Papular urticaria
Viral exanthem
Bullous pemphigoid


WORKUP

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Lab Studies

  • The diagnosis can often be made clinically in patients with a pruritic rash and characteristic linear burrows.

Other Tests

  • Definitive diagnosis of scabies is made by direct visualization of the mite, eggs, or feces. Mineral oil should be placed on the end of a burrow, preferably where a black dot is visible. The area should then be scraped with a number 5 scalpel blade, and the scrapings should be shed onto a slide. The mite can be visualized with low-power microscopy. In infants and young children, 75% of mites can be found on the hands and feet, making these the best sites to examine for burrows.
  • A simple, cheap, sensitive, and specific test for routine diagnosis of active scabies is desirable.2 The expression and purification of S scabiei recombinant antigens have identified a number of molecules with diagnostic potential. Current studies are assessing the accuracy of these recombinant proteins in identifying antibodies in individuals with active scabies and in differentiating them from individuals with past exposure.

Histologic Findings

The female mite is 0.3-0.5 mm in length and has a tortoise-shaped body with 4 pairs of very short legs, 2 pairs in front and 2 in back. The mite also has bristles on its dorsal surface.


TREATMENT

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Medical Care

  • The mainstay of treatment is scabicidal medications. Appropriate application and treatment of all contacts, including family members, is the key to successful treatment. Antipruritic measures and drugs should be used only in conjunction with scabicidal medications.
  • If available, videodermatoscopy can be used to enhance the monitoring of clinical response to treatment and allows for optimal timing of drug application.3 This may minimize the risk of overtreatment, reduce the potential for side-effects, and enhance patient compliance.


MEDICATION

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Scabies is treated with topical antiparasitic medications. The treatment of choice is permethrin 5% lotion. Alternative drug therapy includes precipitated sulfur in 6% petrolatum, lindane, benzyl benzoate, crotamiton, and ivermectin. Topical antibiotics may be used to treat secondarily infected lesions. Compliance to the prescribed regimen is essential to prevent reinfestation or resistant scabies. One study compared the efficacy of ivermectin and benzyl benzoate lotion used to treat scabies in Nigerian patients and found that ivermectin was at least as effective as benzyl benzoate and led to more rapid improvement.4 The efficacy of benzyl benzoate lotion and permethrin were evaluated in a retrospective matched cohort study of pregnant women.5 No adverse effects on pregnancy outcome were reported in patients using either drug.

Drug Category: Scabicidal agents

Mechanisms of action in these agents include depolarization and paralysis of the pests or nervous system stimulation.

Drug NamePermethrin 5% (Elimite, Nix)
DescriptionNeurotoxin that causes paralysis and death in ectoparasites. Most common treatment for scabies. DOC, particularly for infants, young children, and pregnant or breastfeeding women. The lotion should be applied over the entire body, including the face and scalp in infants. It should be left on for 8-12 h and then rinsed. Reapplication 1 wk later is advised; however, no controlled studies have demonstrated that 2 applications are more effective than one application. No cases of scabies resistant to permethrin have been documented.
Adult DoseApply thin film topically over entire body below the head, leave on 8-12 h before washing off with water; may repeat in 1 wk if necessary
Pediatric DoseInfants >2 months: Apply as in adults and also on hairline, neck, scalp, temple, and forehead
Children: Apply as in adults if hair not infested
ContraindicationsDocumented hypersensitivity to permethrin or chrysanthemums
InteractionsNone reported
PregnancyB - Usually safe but benefits must outweigh the risks.
PrecautionsTreatment may temporarily exacerbate the symptoms of itching, redness, and swelling; do not use near eyes or in mucous membranes

Drug NamePrecipitated sulfur 6% in petrolatum
DescriptionOldest known treatment of scabies. It is safe and effective and is the treatment of choice in infants <2 mo and in pregnant or lactating women. Sulfur is less acceptable to patients secondary to its odor and messy application.
Adult DoseApply topically to entire trunk and extremities hs for 3 consecutive nights
Pediatric DoseApply as in adults (see precautions)
ContraindicationsDocumented hypersensitivity to sulfur or sulfonamides
InteractionsNone reported
PregnancyC - Safety for use during pregnancy has not been established.
PrecautionsCaution if applied to irritated or abraded skin; apply in patients <2 y only when supervised by physician (fatalities have been reported in infants after application to large surface areas for treatment of scabies); avoid contact with eyes

Drug NameLindane 1% (gamma benzene hexachloride, Kwell)
DescriptionPrevious DOC for scabies, now considered second-line treatment if other agents fail or are not tolerated. Not safe in children because of transcutaneous absorption that leads to neurotoxicity. Overall, permethrin is a safer choice.
Adult DoseApply thin film topically over entire body below the head, leave on 8-12 h before washing off with water; may repeat in 1 wk if necessary; not to exceed 30 g/application
Pediatric DoseInfants and children: Apply thin film topically over entire body including hairline, neck, scalp, temple, and forehead, leave on 6-8 h before washing off with water; may repeat in 1 wk if necessary; not to exceed 30 g/application
ContraindicationsDocumented hypersensitivity; neonates; acutely inflamed skin or raw weeping surfaces
InteractionsOil-based hair dressing may increase toxic potential
PregnancyB - Usually safe but benefits must outweigh the risks.
PrecautionsCaution in patients with history of seizures; do not apply to eyes, face, or mucous membranes; caution in history of keratinization or ichthyosis disorders

Drug NameCrotamiton 10% (Eurax)
DescriptionUsed for the treatment of scabies. Mechanism of action is unknown. Associated with frequent treatment failures.
Adult DoseWash thoroughly and scrub away any loose scales, apply thin layer topically from neck to toes, and gently massage into skin and leave on; a second application should be applied after 24 h; bathe 48 h after the last application
Pediatric DoseInfants and children: Apply as in adults
ContraindicationsKnown hypersensitivity
InteractionsNone reported
PregnancyC - Safety for use during pregnancy has not been established.
PrecautionsTreatment may temporarily exacerbate the symptoms of itching, redness, and swelling; do not apply to face, urethral meatus, eyes, mucous membranes, or swollen skin

Drug NameIvermectin (Mectizan, Stromectol)
DescriptionSynthetic derivative of the antiparasitic class of compounds called avermectins. This macrolide endectocide is active not only against scabies but also against head lice, demodicidosis, cutaneous larva migrans, cutaneous larva currens, myiasis, and filariasis. Currently approved for the treatment of human onchocerciasis and strongyloidiasis. Although not FDA-approved for the treatment of scabies, it is widely used and literature supports its use.
Binds selectively with glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death. Half-life is 16 h; metabolized in liver. It kills the mites but does not affect the eggs.
Ivermectin has been researched recently as a PO treatment for scabies. A single dose PO has also been found to be highly efficacious in the treatment of scabies in patients with HIV. Still in the early stages of trial.
Adult Dose200 mcg/kg PO once; a repeat dose may be necessary if the patient is infected with Norwegian scabies or in patients with immunocompromise; repeat dosing requires further evaluation
Pediatric Dose<15 kilograms: Not established
>15 kilograms: Administer as in adults
ContraindicationsDocumented hypersensitivity
InteractionsMay interact with other ligand-gated chloride channels, such as those gated by GABA
PregnancyC - Safety for use during pregnancy has not been established.
PrecautionsCaution in women who are breastfeeding; may cause nausea, vomiting, drowsiness, or mild CNS depression; patients with hyperreactive onchodermatitis may develop a severe immune reaction (ie, Mazzotti reaction) consisting of optic neuritis, chorioretinitis, proteinuria, pruritus, rash, and edema

Drug Category: Topical antibiotics

These agents are used to treat lesions with secondary infection.

Drug NameMupirocin (Bactroban)
DescriptionUsed to treat Staphylococcus species, beta-hemolytic streptococci, and Streptococcus pyogenes. Inhibits protein and RNA synthesis by inactivating transfer-RNA synthetase.
Adult DoseApply a small amount topically to the affected areas 2-5 times daily for 5-14 d
Pediatric DoseApply as in adults
ContraindicationsKnown hypersensitivity
InteractionsNone reported
PregnancyB - Usually safe but benefits must outweigh the risks.
PrecautionsProlonged use may result in overgrowth of nonsusceptible organisms; do not compound with Aquaphor, coal tar solution, or salicylic acid

Drug Category: Topical corticosteroids

These agents may be applied to help control intense pruritus caused by scabies.

Drug NameHydrocortisone, topical (Cortaid, Dermacort, Westcort, CortaGel)
DescriptionAn adrenocorticosteroid derivative suitable for application to skin or external mucous membranes. Has mineralocorticoid and glucocorticoid effects that result in anti-inflammatory activity. Considered to be the lowest-potency topical steroid.
Adult DoseApply topically to affected areas sparingly tid/qid
Pediatric DoseApply as in adults
ContraindicationsDocumented hypersensitivity; viral, fungal, and bacterial skin infections
InteractionsNone reported
PregnancyC - Safety for use during pregnancy has not been established.
PrecautionsProlonged use, applying over large surface areas, application of potent steroids, and use of occlusive dressings may increase systemic absorption and may cause Cushing syndrome, reversible HPA-axis suppression, hyperglycemia, thinning of skin, or glycosuria


FOLLOW-UP

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Further Inpatient Care

  • Patients may need to be reexamined at 2 weeks and again one month after treatment. Persistent pruritus after treatment does not necessarily reflect treatment failure. Hypersensitivity reaction may outlast the presence of live parasites. Antihistamines and topical corticosteroids may be used to control pruritus until symptoms resolve. If a patient has persistent lesions at the 1-month check-up, reinfection or persistent infection should be suspected. In this case, treatment should be reinitiated. The family or any close contacts should also be examined to check for a source of reinfection.

Further Outpatient Care

  • All family members and close contacts should be treated, even if asymptomatic, to prevent reinfection. All bed linen and clothing should be washed in order to remove eggs and mites. Fomites can persist for 2-3 days without a host. Articles that cannot be washed should be kept in sealable plastic bags for 3 days.

Complications

  • Secondary lesions may occur from scratching and include excoriated papules and crusted areas. These lesions may become secondarily infected. Topical antibiotics can be used to treat minor superinfection and oral antibiotics may be required in patients with more extensive infection. The most common infectious agents are skin flora, including Staphylococcus and Streptococcus species.

Prognosis

  • Scabies has an excellent prognosis. If one medication is ineffective, multiple treatments with scabicides or sequential use of several agents can be curative.

Patient Education

  • Education is extremely important. The mode of transmission is via human contact, as well as via fomites. All close contacts must be treated, or reinfection will occur.
  • For excellent patient education resources, visit eMedicine's Infections Center and Children's Health Center. Also, see eMedicine's patient education articles Scabies and Skin Rashes in Children.


MULTIMEDIA

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Media file 1:  Scabies mite. Courtesy of William D. James, MD.
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Media file 2:  Scabies mite scraped from a burrow (400 X). Courtesy of Audra Malerba, DO.
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Media file 3:  Scabies. Courtesy of William D. James, MD.
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Media file 4:  In patients with crusted scabies, sections show multiple mites (arrows) within the hyperkeratotic stratum corneum. The epidermis is spongiotic (hematoxylin and eosin [H&E], 100 X). Courtesy of Audra Malerba, DO.
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Media type:  Photo

Media file 5:  In patients with routine scabies, a single mite is observed. Eosinophilic spongiosis may be present (hematoxylin and eosin [H&E], 400 X). Courtesy of Audra Malerba, DO.
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Media file 6:  In patients with scabies, erythematous vesicles and papules are present on torso extremities, some with adjacent linear excoriations. Courtesy of Audra Malerba, DO.
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Media file 7:  Scabies on hand. Courtesy of William D. James, MD.
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Media file 8:  Norwegian scabies. Courtesy of William D. James, MD.
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Media file 9:  Scabies on leg. Courtesy of William D. James, MD.
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Media file 10:  Scabies on buttocks. Courtesy of William D. James, MD.
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Media file 11:  Scabies on penis. Courtesy of William D. James, MD.
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Media file 12:  Scabies on penis. Courtesy of Hon Pak, MD.
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REFERENCES

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Scabies excerpt

Article Last Updated: Jun 14, 2007