Urticaria Skin Condition Quiz: Test Your Knowledge of Hives

Acute urticaria results from allergen-triggered mast cell degranulation in the dermis. Histamine release increases vascular permeability, causing erythematous, warm, serpiginous papules. Rapid onset within hours strongly supports hypersensitivity. Hereditary angioedema presents with deeper swelling rather than superficial wheals. Physical abuse and topical irritation rarely produce transient migratory lesions. The short timeline and morphology make allergic activation the most likely mechanism.

HSV-1 typically produces grouped vesicles on an erythematous base. Lesions are painful and recur in similar locations due to viral latency in trigeminal ganglia. Zoster follows dermatomal distribution and usually presents with systemic symptoms. Staphylococcal infections produce pustules or abscesses. The localized distal nasal involvement without dermatomal spread strongly supports HSV-1 reactivation.

Oral terbinafine inhibits fungal squalene epoxidase, disrupting ergosterol synthesis. Continuous 12-week therapy achieves high cure rates because systemic circulation delivers drug into the nail matrix. Topical agents fail due to limited penetration through the keratinized nail plate. Griseofulvin has lower efficacy. Sustained systemic exposure ensures fungal eradication and reduces relapse rates.

Xerosis is age-related epidermal dehydration due to impaired stratum corneum barrier function. Reduced lipid content increases transepidermal water loss. Cold weather decreases ambient humidity, worsening dryness. Resulting fissures and erythema cause pruritus. Distribution on trunk and extremities without venous changes excludes stasis dermatitis. Clinical pattern and seasonality support xerosis.

Keratoacanthoma grows rapidly over weeks and forms a dome-shaped nodule with central keratin plug. It may involute spontaneously within months. Squamous cell carcinoma resembles it but does not regress. Rapid growth followed by spontaneous resolution strongly supports keratoacanthoma. Histologic evaluation is required because differentiation from carcinoma can be challenging.

Scabies spreads primarily through prolonged direct skin contact. The Sarcoptes scabiei mite burrows into the stratum corneum. Bedding transmission is uncommon. Children often have facial involvement, unlike adults. Absence of reported family itching does not exclude diagnosis because contacts may underreport symptoms. Transmission mechanism confirms direct contact.

Positive surgical margins indicate residual carcinoma. Basal cell carcinoma can extend microscopically beyond visible edges. Reexcision ensures complete removal and reduces recurrence risk, particularly on the face where tissue conservation and cosmetic outcome are important. Topical or destructive methods are inappropriate for residual invasive tumor.

Benzoyl peroxide generates free radicals that oxidize bacterial proteins, reducing Cutibacterium acnes colonization. Unlike retinoids, which normalize keratinization, benzoyl peroxide directly decreases inflammatory lesions. Its antibacterial action reduces pustules and papules. Resistance development is uncommon due to oxidative mechanism.

Erythema nodosum presents as bilateral tender subcutaneous nodules, commonly on shins. It represents panniculitis triggered by infections, medications, or systemic disease. Oral contraceptives are a known cause. Lesions are deep, warm, and symmetric, distinguishing them from trauma or superficial inflammation.

Herpetic whitlow arises from HSV inoculation into broken skin. Vesicles coalesce and may appear purulent. Regional lymphadenopathy and fever occur due to viral replication. Healthcare workers are at risk from oral secretions. Bacterial infections produce localized abscess without grouped vesicles.

Candida species cause most chronic paronychia cases. Chronic moisture disrupts nail fold barrier, allowing fungal colonization. Acute bacterial infections are more often staphylococcal. Persistent inflammation and cuticle separation favor Candida growth. Antifungal therapy is required for resolution.

The mite burrow is pathognomonic for scabies. It appears as a thin, serpiginous line caused by female mites tunneling into superficial epidermis. Identification confirms infestation. Secondary excoriations may obscure burrows.

Topical antifungals poorly penetrate the dense keratin of toenails. Infection resides in the nail matrix and bed, areas inaccessible to surface treatment. Systemic therapy delivers drug through bloodstream into growing nail. Limited permeability explains lower topical cure rates.

Herpes zoster follows a dermatomal distribution reflecting reactivation along a single sensory nerve. HSV lesions recur locally without strict dermatomal pattern. Dermatomal spread distinguishes zoster clinically.

Xerosis results from decreased lipid production and impaired keratinocyte maturation. Reduced hydration weakens barrier integrity, causing scaling and fissures. Environmental dryness worsens transepidermal water loss. This dehydration mechanism explains pruritus and plaque formation.