Quick Comparison
| Aloe Vera | Urea | |
|---|---|---|
| Typical Concentration | Apply pure aloe vera gel or products containing high concentrations (>50% aloe). For sunburn: apply liberally and frequently. For daily use as a soothing moisturizer: apply after cleansing. Refrigerating aloe gel provides additional cooling relief. | Moisturizing: 2-10%. Mild exfoliation: 10-20%. Strong keratolytic: 20-40%. For face: stay at 5-10%. For body rough patches: 10-20%. For calluses/severely rough skin: 40%. Apply to damp skin and seal with cream. |
| Application | Topical (gel, cream, lotion). Pure inner leaf gel or standardized extracts. Apply to clean skin. | Topical (cream, lotion, gel). Apply to damp skin. Eucerin and CeraVe have well-known urea-containing lines. |
| Research Papers | 10 papers | 10 papers |
| Categories |
Mechanism of Action
Aloe Vera
Acemannan (acetylated mannan polysaccharide) is the primary bioactive—it binds to macrophage mannose receptors and stimulates macrophage phagocytosis, cytokine release (IL-1, TNF-α), and fibroblast proliferation via growth factor induction, accelerating wound healing and granulation tissue formation. Acemannan also promotes keratinocyte proliferation and migration. Aloesin (a chromone) inhibits tyrosinase and tyrosinase-related protein-1 (TRP-1), providing mild brightening. Aloe-emodin has antibacterial activity against Gram-positive bacteria and antiviral effects. Salicylic acid naturally present in aloe inhibits cyclooxygenase (COX), providing mild anti-inflammatory and analgesic effects. The gel matrix forms a semi-occlusive film that reduces transepidermal water loss (TEWL). Aloe contains glucomannan, which acts as a humectant. Proteolytic enzymes (bradykinase) may contribute to anti-inflammatory activity. Use inner leaf gel to avoid anthraquinones in the latex that can cause irritation.
Urea
At low concentrations (<10%), urea acts as a humectant — small molecule (60 Da) absorbing into stratum corneum, drawing water via hydrogen bonding to carbonyl and amine groups. Part of endogenous NMF (filaggrin degradation products with amino acids, lactate), highly biocompatible. Integrates into corneocyte envelope, supports aquaporin-3 water transport. At higher concentrations (>10%), denatures keratin (K1, K10) by disrupting hydrogen bonds in alpha-helical structure and disulfide bridges in cornified envelope, causing corneodesmosome degradation and desquamation. Keratolytic via direct protein denaturation, not enzymatic. Dual mechanism — humectant at low dose, keratolytic at high — versatile for hydration and hyperkeratotic conditions (psoriasis, keratosis pilaris).
Risks & Safety
Aloe Vera
Common
May cause drying if used alone (aloe lacks occlusive properties, so moisture can evaporate).
Serious
None from topical use.
Rare
Allergic contact dermatitis (especially to compounds in the latex/outer leaf, not the inner gel). Oral aloe vera is a separate concern with laxative effects.
Urea
Common
Stinging on broken or irritated skin (more likely at higher concentrations).
Serious
None.
Rare
Contact dermatitis (uncommon).
Full Profiles
Aloe Vera →
One of the oldest and most recognized soothing ingredients, used for millennia for burns, wounds, and skin irritation. Aloe vera gel contains over 75 active compounds including polysaccharides, vitamins, minerals, and enzymes. It provides immediate cooling, hydration, and anti-inflammatory relief. The evidence is strongest for wound healing, sunburn recovery, and moisturization.
Urea →
A natural component of the skin's Natural Moisturizing Factor (NMF) that serves as both a humectant and a keratolytic depending on concentration. At low concentrations (2-10%), urea hydrates by drawing water into the stratum corneum. At higher concentrations (20-40%), it breaks down keratin protein, making it a powerful treatment for rough, thickened, or keratotic skin conditions like keratosis pilaris, calluses, and psoriasis.