Science
Mechanism of Action
The key active molecule, Lawsone, functions by activating the Aryl Hydrocarbon receptor (AhR), which is integral to skin homeostasis, tissue regeneration, infection response, and inflammation. Lawsone influences keratinocyte activity by inhibiting proliferation and accelerating differentiation, thereby impacting tissue regeneration and exhibiting anti-inflammatory effects. Its antimicrobial efficacy is attributed to numerous free hydroxyl groups that interact with bacterial cell wall carbohydrates and proteins, leading to enzyme inactivation.
Research
Clinical Evidence
Low confidence1%
Transparency
Dusting Analysis
Clinical investigations have evaluated henna at a 1% concentration for topical skin applications, and cosmetic extracts are documented for use between 0.5-5% in formulations. This suggests the ingredient is often incorporated at concentrations intended to be functionally active, rather than merely for label claims.
The Formula
Formulation
Stability
Henna extracts are commonly dissolved in water and glycerin for formulation. For optimal dye release from henna powder, a mildly acidic pH, typically around 5.5 (e.g., with lemon juice), is beneficial for prolonging the activity of lawsone precursors. Commercial henna extracts generally maintain stability within a pH range of 4-7.
Conflicts
- Para-phenylenediamine (PPD) and other synthetic dyes (often present in 'black henna' and linked to severe allergic reactions, chemical burns, and scarring).
- Oils or curd (when the objective is maximum dye uptake from henna powder, as these can impede the process).
Safety
Safety Profile
The FDA has granted approval for henna solely as a hair dye in the United States, not for topical use on the skin. The Cosmetic Ingredient Review (CIR) Expert Panel has deferred its evaluation, referencing the FDA's assessment. The European Commission's Scientific Committee on Consumer Products (SCCS) reviewed henna and concluded that a safe use level for skin could not be identified. It is crucial to differentiate pure henna from 'black henna,' which frequently contains para-phenylenediamine (PPD) and other synthetic dyes known to induce severe allergic reactions, chemical burns, and permanent scarring when applied to skin.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Despite some observed benefits in specific skin conditions and demonstrable antimicrobial properties, the absence of an identified safe use level by regulatory bodies like the SCCS and the FDA's approval solely for hair dye raise significant safety concerns for general topical skin application.
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