Pruritus

Pruritus is the desire to scratch that is induced by unpleasant cutaneous sensations caused by histamines and other endogenous substances. Atopic dermatitis is one of the most common childhood skin diseases; emergencies include severe angioedema/anaphylaxis and Stevens-Johnson syndrome. Topical preparations are common allergens.

Differential Diagnosis

• Urticaria
  –Hypersensitivity reaction causing edema via mast cell/basophil release of histamine, kinins, prostaglandins, and serotonin, mostly IgE-mediated
  –Hives; subcutaneous and mucous membranes
  –Angioedema: Most cases acute (resolving within 48 hours); chronic >6 weeks
  –Anaphylaxis: May be life-threatening

• Atopic dermatitis
  –Incidence 2–10%; often begins in infancy
  –Most cases improve with age
  –Frequent remissions/exacerbations
  –Increased risk of infection (herpes, eczema herpeticum; staph, strep)
  –Can be exercise-induced
• Xerosis (dry skin)
  –Idiopathic or due to excessive bathing, low humidity, etc.
• Tinea (dermatophytoses, “ringworm”)
  –Fungal infection (Trichophyton, Microsporum, Epidermophyton)
  –Scalp (tinea capitis), face, trunk, extremities (t. corporis), feet (t. pedis)
  –complications: superinfection and kerion
  • Contact dermatitis
    –Allergens (poison ivy, cosmetics, dyes, drugs, foods, jewelry/nickel, animals)
    –Irritants (soap, chemicals, wool, fiberglass)
  • Scarlet fever (group A strep): “Sandpaper rash,” incubation period 1–7 days; age 5–15 years, 15–20% colonized (oropharyngeal)
  • Herpes: Varicella, zoster, herpes simplex
  • Lice (pediculosis): Head or pubic area
  • Mites (scabies [Sarcoptes scabiei])
  • Pinworms (Enterobius vermicularis)
  • Cholestasis (TPN, biliary atresia)
  • Erythema multiforme (“bull's eye rash”): Stevens-Johnson syndrome
  • Drug-induced: Opiates, barbiturates, isoniazid, phenothiazines, erythromycin
  • Systemic diseases: Malignancies, renal failure, mastocytosis, SLE, JRA, hypo- and hyperthyroidism, DM
  • Prurigo gestationis
  • Parasites (“swimmer itch,” trematodes)
  • Chronic skin diseases (psoriasis)

  Workup and Diagnosis

  • History and physical exam
    –Location, duration, rash, exposure, chronic illness, associated symptoms, ill contacts
    –Urticaria: Exposure to foods, drugs, bacteria, viruses, insect bites, etc.; wheals (erythematous, raised, well-circumscribed lesions) usually self-limited; may also have angioedema, wheezing, stridor, hoarseness, anaphylaxis, hypotension
    –Atopic dermatitis: Family history; ill-defined, erythematous, scaly plaques; in infant, head, extensor surfaces, and trunk; in child, antecubital/popliteal fossae, neck, wrist/ankle; may also have Morgan folds (lines under lower eyelids)
    –Tinea: Erythematous, scaly, circular plaque with central clearing; kerion is inflammatory, painful mass with sterile pustules and regional lymphadenopathy
    –Poison ivy: Linear streaks of vesicles, may last several weeks; exposure to poison ivy, oak, or sumac
    –Lice: Nits on hair shafts
    –Mites: 1–2 mm papules and burrows on palm, sole, interdigital web, axilla, genitalia, wrist, ankle
    –Pinworm: Nocturnal anal pruritus
    –Scarlet fever: Erythematous, finely granular rash, most prominent in axilla and groin, circumoral pallor
  • Pinworm: Apply tape to anus, see microscopic egg
  • Scarlet fever: Throat culture or antigen detection
  • Tinea: KOH preparation, culture, or Wood lamp to confirm diagnosis (usually diagnosed clinically)

  Treatment

  • Urticaria: Antihistamine; if nonresponsive, corticosteroid, avoid triggers
  • Severe angioedema/anaphylaxis
    –Epinephrine 1:1,000, 0.01 mg/kg SC every 15 minutes
    –Maximum dose 0.3 mg, IV fluids for hypotension
    –Give epinephrine kits to patient for self-administration
  • Atopic dermatitis: Topical corticosteroid or nonsteroidal immunosuppressant (e.g., pimecrolimus), oral antihistamine, moisturizing agent, room humidifier; avoid heat, stress, wool
    
  • Tinea: Topical antifungals, oral for tinea capitis
  • Poison ivy: Topical or systemic corticosteroid
  • Scarlet fever: Penicillin (to prevent rheumatic fever)
  • Lice/mites: Topical permethrin
    –Consider sexual abuse if pubic lice
  • Pinworm: Mebendazole or pyrantel pamoate
  • Avoid scratching/heat/tight clothing
  • Tepid water bath, moisturizer, topical anesthetic

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

Other Book Chapters Related to Rash

Read excerpts from these other book chapters related to Rash:

Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2008 Williams & Wilkins.

More About Causes of Rash

• Back to symptom: Rash: Introduction (review 1085 causes)
• Next Book Extract About Rash: Urticaria (In A Page: Pediatric Signs and Symptoms)
• All Book Extracts: All Online Book Extracts for Rash

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9