Generic Name

Zinc oxide

Mechanism

• Physical UV blocker: Forms a translucent film that reflects and scatters UVA/UVB radiation, preventing epidermal penetration.
• Skin barrier reinforcement: Creates a semi‑occlusive layer that reduces transepidermal water loss and shields the epidermis from mechanical irritation.
• Anti‑inflammatory effect: Reduces local cytokine release (e.g., IL‑1α, IL‑6) and down‑regulates COX‑2 activity, mitigating erythema and edema in contact dermatitis and mild burns.
• Antimicrobial synergy: At low concentrations it can inhibit bacterial adhesion on compromised skin, complementing barrier function.

Pharmacokinetics

• Absorption: Minimal systemic uptake when applied to intact skin (<0.001 % of dose reaches circulation); higher when skin is broken or occluded but remains below therapeutic thresholds.
• Distribution: Primarily remains within the stratum corneum; negligible protein binding in plasma.
• Metabolism: No significant hepatic or renal metabolism; remains as elemental zinc.
• Elimination: Excreted unchanged via feces (via skin desquamation) and urine (trace amounts); half‑life not clinically relevant.

Indications

• Solar protection: Broad‑spectrum SPF ≥ 10 for infants, children, and adults.
• Dermatologic irritation: First‑line treatment for diaper dermatitis, mild eczema, and mild contact dermatitis.
• Minor burns and abrasions: Reduces pain and promotes re‑epithelialization.
• Wound dressings: Used as a protective barrier over gauze or sterile dressings in surgical sites.
• Photoprotection in photosensitive disorders: Adjunct in lupus erythematosus or xeroderma pigmentosum.

Contraindications

• Allergy to zinc: Rare hypersensitivity reaction (contact dermatitis, urticaria).
• Open, deep wounds: Use with caution; may impede wound healing if applied excessively.
• Under occlusive dressings: May cause maceration or local irritation; monitor skin integrity.
• Pregnancy & lactation: Generally considered safe; minimal systemic absorption precludes teratogenic risk.
• Inhalation risk: Avoid inhalation of powdered formulations, especially in infants (risk of lung deposition).

Dosing

• Sunburn / sun protection: Apply generously (≈0.3 mg cm⁻²) to exposed skin 30 min before sun exposure; reapply every 2 h or after swimming/sweating.
• Dermatitis or diaper rash: 1–2 mg cm⁻² applied 2–3× daily; may use as a protective layer under diaper.
• Minor burns: Cover with a thin film; no need for occlusion; apply 2–4 × daily until re‑epithelialization.
• Wound dressing: Thin layer over sterile gauze; replace dressing as per wound‑care protocol.

Important: Use the product with the highest SPF needed for the situation; do not exceed the recommended thickness, as it may reduce occlusive efficacy.

Adverse Effects

• Local irritation: Pruritus, erythema, mild contact dermatitis (especially in sensitive skin).
• Staining: Residual white cast on clothing or bedding.
• Rare systemic: Hypozincemia from chronic, extensive use; presents as hair loss, anemia, or growth delay in children.
• Serious: Allergic contact dermatitis, severe skin irritation leading to secondary infection.

Monitoring

• Skin integrity: Inspect for signs of maceration, worsening erythema, or allergic reaction.
• Compliance: Ensure adequate coverage for photoprotection; educate on re‑application intervals.
• Systemic exposure: Monitor serum zinc levels only in chronic, high‑dose users or in cases of unexplained anemia.
• Photoprotection efficacy: Verify adequate SPF and check for tanning or sunburn despite use.

Clinical Pearls

• Use “Zinc‑oxide first, then fragrance”: Avoid adding fragrance or other irritants to the base formulation; they are the most common trigger of dermatitis.
• Barrier layering: In diaper rash, apply a thin layer of zinc oxide followed by a non‑occlusive diaper; the zinc layer acts as a physical barrier to fecal enzymes.
• Photoprotection synergy: Combine zinc oxide with organic filters (e.g., octocrylene) in broad‑spectrum sunscreens to cover the full UV spectrum and improve cosmetic acceptance.
• Burn care tip: For superficial burns, keep the wound dry and apply zinc oxide only after the blistering phase; avoid occlusion to prevent bacterial overgrowth.
• Storage: Keep away from heat and direct sunlight to prevent powder degradation; store in a cool, dry place to preserve the particle integrity.

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• Key takeaways: Zinc oxide topical is a versatile, low‑risk agent that serves as a UV filter, barrier enhancer, and anti‑inflammatory moisturizer. Its minimal systemic absorption makes it ideal for use in vulnerable populations, including infants and patients with chronic skin conditions.