What factors influence the rate of dermal absorption of essential oils?

Skin Barrier Integrity: Damaged or compromised skin (e.g., wounds, eczema) exhibits higher absorption rates.
Skin Hydration Level: Moist skin (e.g., after bathing) absorbs substances faster than dry skin.
Skin Thickness: Thin-skinned areas (e.g., face, neck) absorb more rapidly than thick-skinned regions (e.g., palms, soles).
Age Factor: Infants and the elderly have thinner skin with higher absorption rates; adults possess stronger skin barriers and slower absorption.
Regional Skin Variation: Permeability varies across body parts, e.g., abdominal skin absorbs better than the arms.

Molecular Size and Structure: Small-molecule oils (e.g., menthol) absorb more easily than large-molecule oils (e.g., resins); liposoluble oils (e.g., tea tree oil) penetrate faster than water-soluble oils.
Essential Oil Concentration: Higher concentrations may increase absorption rates, but excessively high levels can cause skin irritation, reducing efficiency.
Volatility: Highly volatile oils (e.g., citrus oils) evaporate quickly, shortening skin contact time and lowering absorption.
Purity and Composition: Pure essential oils absorb better than diluted or adulterated oils; specific components (e.g., terpenes) enhance permeability.

Carrier Oil Type: Light carrier oils (e.g., jojoba oil) promote absorption, while heavy oils (e.g., mineral oil) may form a barrier hindering absorption.
Formulation Type: Emulsions or gel formulations absorb more readily than pure essential oils; adding penetration enhancers (e.g., ethanol, lecithin) significantly boosts rates.
Blending Ratio: The ratio of essential oil to carrier oil affects absorption; a 1-5% concentration is typically recommended for optimal penetration.

Application Method: Massaging or rubbing the skin increases blood flow and stratum corneum penetration, enhancing absorption; occlusive dressing (e.g., warm compress) amplifies effects.
Temperature: Warm environments or heated applications (e.g., warmed oils) dilate pores, accelerating absorption; cold environments slow it down.
Humidity: High humidity maintains skin hydration, promoting absorption; low humidity may dry the skin, reducing rates.
Exposure Duration: Prolonged skin contact (e.g., 10-15 minutes) allows fuller absorption than brief application.

Individual Variability: Genetic factors and skin type (e.g., oily vs. dry) influence absorption efficiency.
Health Status: Metabolic diseases (e.g., diabetes) or skin disorders (e.g., psoriasis) may alter absorption kinetics.
Drug Interactions: Concurrent use of other topical products (e.g., ointments) may compete with or interfere with essential oil absorption.