Generic Name

Urea

Mechanism

Urea is a small, naturally occurring organic compound that serves as a key denominator in several topical formulations for dermatologic conditions. Its main actions include:
• Hydration & Humectancy – Urea dissolves in water, attracting moisture into the stratum corneum, enhancing skin hydration.
• Keratolysis – At concentrations > 10 %, urea disrupts hydrogen bonds between keratin filaments, softening hyperkeratotic scales and facilitating shedding.
• Enzyme Modulation – Urea inhibits protease activity that contributes to abnormal cornification, thereby normalizing skin turnover.
• Barrier Function Restoration – Improved lipids and corneocyte cohesion reduce transepidermal water loss.

These properties make urea an effective, non‑irritating, dual‑mechanism agent for xerosis, hyperkeratosis, and various dry dermatoses.

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Pharmacokinetics

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Indications

• Xerosis and Dyshidrotic Eczema – 10–20 % formulations reduce fissuring and pruritus.
• Psoriasis (plaque, inverse, palmoplantar) – 10–30 % mixes soften scales, aid barrier repair.
• Ichthyosis, Keratosis Pilaris, Lichen Spinulosus – Hydration leading to plaque lysis.
• Dry dermatitis & seborrheic dermatitis – improves complexion and reduces scaling.
• Hair shedding (telogen effluvium) – 5% solutions maintain scalp hydration.
• Certain cosmetic products (anti‑aging, humectants) – enhance skin softness and elasticity.

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Contraindications

• Dermatitis herpetiformis – use cautiously; may worsen itching.
• Severe skin barrier disruption – increased absorption may cause local irritation.
• Recent skin trauma or post‑procedure – can delay healing.
• Known hypersensitivity to urea – rare but possible contact dermatitis.
• Open wounds or ulcers – avoid; may cause stinging.
• Use in combination with other keratolytics (e.g., salicylic acid) – risk of additive irritation.

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Dosing

• Application tip – Apply a thin film over affected area, massage gently; any stinging indicates too high a concentration.
• Systemic use – No approved oral formulation; only topical or saline irrigant (rare in veterinary).

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Adverse Effects

Common
• Mild erythema or burning at the site of application.
• Transient scaling or “crisp” sensation during keratosis resolution.

Serious (rare)
• Allergic contact dermatitis (erythema, vesiculation).
• Systemic absorption leading to hyperammonemia is exceedingly rare in topical therapy.
• Exacerbation of eczema or psoriasis when used alone at high concentrations.

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Monitoring

• Skin tolerance – Assess for erythema, irritation, or worsening lesions after 2–3 days.
• Efficacy – Improvement in scaling, fissure resolution, or decreased pruritus by 30–50 % within 4‑6 weeks.
• Patient compliance – Complex regimens (10 % urea 2× daily) often need reminders for sustainable outcomes.

For patients using high‑concentration formulations with concomitant steroids, monitor for skin atrophy or telangiectasia.

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Clinical Pearls

• “Urea is a ‘meta‑treatment’” – It hydrates *and* gently breaks down hyperkeratotic debris, making it superior to plain moisturizers for scaling skin.
• Begin low, build up – Start at 5 % for patients with sensitive skin; spike to 10–20 % only after clinical tolerance.
• Use with a barrier repair cream – Pair high‑concentration urea with ceramide‑rich formulas to restore lipids once keratosis has cleared.
• Short-term high dose, then taper – A “pulse” strategy (1–2 × daily for 3 weeks, followed by 1×/week) can minimize local irritation.
• Avoid mixing with salicylic acid or glycolic acid – The combined keratolysis may cause excessive desquamation and stinging.
• Urea ≠ “dry cure” – It should never replace fragrance‑free emollients; it is a preparatory step to increase delivery of subsequent potent therapies.
• Examine comorbidities – In patients with kidney dysfunction, use only topical formulations to avoid theoretical hyperuremia; never use oral preparations unless under specialist supervision.
• Keep concentration clear – Labeling errors can lead to unintended 40 % exposures—possible systemic absorption and renal overload.

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• References – For detailed evidence, consult *Dermatology* (2023) update on keratolytic agents, *J Am Acad Dermatol* (2022) on urea formulations, and FDA DMID guidance on topical urea products.