Science
Mechanism of Action
Tar Oil primarily acts by activating the aryl hydrocarbon receptor (AHR) signaling pathway, which promotes epidermal differentiation and increases filaggrin levels, leading to enhanced skin barrier integrity. It also inhibits the IL-4/STAT6 pathway, moderating keratinocyte inflammatory responses relevant to atopic dermatitis. Furthermore, its antiproliferative effects reduce DNA synthesis and mitotic activity, normalizing keratinization, while also possessing antimicrobial, anti-inflammatory, and antipruritic properties.
Research
Clinical Evidence
High confidenceN/A
Key findings
- 01 Dermatologists routinely prescribe 2-5% coal tar in emollient bases, often alongside UV radiation therapy, to effectively mitigate redness, itching, and inflammation in chronic plaque psoriasis.
- 02 One study observed that a lotion containing 1% coal tar extract provided superior patient outcomes compared to a 5% coal tar extract formulation.
- 03 A formulation with 7.5% Solution Coal Tar U.S.P. (equivalent to 1.5% Coal Tar) is specifically developed for psoriasis and eczema, helping to normalize skin cell proliferation, alleviate inflammation, and relieve itching.
- 04 Topical products incorporating up to 2.3% w/w pine tar oil are utilized for treating eczema, dermatitis, psoriasis, sunburn, and other dry, itchy, and inflamed skin conditions.
- 05 A 15% liquor carbonis distillate (LCD) solution demonstrated comparable efficacy, tolerability, and cosmetic acceptability to calcipotriene 0.005% cream in patients with moderate, chronic plaque psoriasis.
- 06 A 2% coal tar foam, when synergistically combined with clobetasol propionate 0.05% emollient foam, effectively induced remission in localized plaque psoriasis.
Transparency
Dusting Analysis
Tar oil, particularly coal tar, is recognized by the FDA as a Category I (safe and effective) OTC drug ingredient for specific dermatological conditions, indicating a robust clinical foundation rather than being a cosmetically 'dusted' ingredient.
The Formula
Formulation
Stability
Interfacial tension between coal tar and water remains stable within a pH range of 3.4 to 9.1. A sharp decrease in interfacial tension above pH 9.1 could compromise emulsion stability. As a component, coal tar enhances moisture resistance, UV resistance, and thermal stability in formulations.
Synergies
- Emollient bases (for enhanced delivery and skin comfort)
Conflicts
- Sunlight exposure (due to photosensitization by polycyclic aromatic hydrocarbons)
- Light-colored hair and clothing (risk of temporary staining)
Safety
Safety Profile
Tar Oil, specifically Coal Tar, is monographed by the FDA as a Category I (safe and effective) OTC drug ingredient for treating dandruff, seborrhea, and psoriasis within concentrations of 0.5-5%. For cosmetic formulations not utilized as OTC drugs, the CIR Expert Panel suggests concentrations that do not exert a biological effect, pending further safety data. Potential side effects include skin irritation, rashes, unpleasant odor, stinging or burning sensations, and temporary discoloration of hair and clothing. Its polycyclic aromatic hydrocarbon (PAH) components are photosensitizers, leading to potential phototoxicity and increased sun sensitivity. While animal studies have indicated an increased risk of skin cancer, human epidemiological studies over 75 years have not linked coal tar therapy with an increased incidence of cancer. However, tar oil is classified as a potential carcinogen by OSHA and IARC.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Tar oil is a valuable, FDA-recognized active ingredient highly effective for managing chronic inflammatory skin conditions like psoriasis and eczema, yet careful formulation and user guidance are essential due to potential irritation, photosensitivity, and staining.
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