Coal Tar for Seborrheic Dermatitis: A Research Summary

Coal tar has a long history of use in dermatology for treating various skin conditions like psoriasis, eczema, and seborrheic dermatitis (dandruff). In this article, we’ll take a look at the research behind using coal tar to treat seborrheic dermatitis.

What is Coal Tar?

Coal tar is a thick, dark liquid that is a byproduct of the process of converting coal into coke or gas [1]. It contains over 10,000 different chemicals, including polycyclic aromatic hydrocarbons (PAHs) [2].

Medicinally, coal tar has been utilized for over 150 years. It has anti-inflammatory, antibacterial, antifungal, antipruritic (anti-itch), and keratoplastic (modifies skin growth) properties [3, 4].

Mechanism of Action

Coal tar works through multiple mechanisms:

• Slows skin cell reproduction: Coal tar reduces the excessive skin cell production associated with psoriasis and seborrheic dermatitis [2].
• Normalizes inflammation: It reduces cytokine and chemokine production, lowering inflammation [5].
• Reduces sebum production: Seborrheic dermatitis involves increased sebum production. Coal tar normalizes this [2].
• Kills fungi: It has antifungal effects against malassezia yeasts implicated in seborrheic dermatitis [3].

Efficacy Against Fungi

There are two key studies examining coal tar’s antifungal effects:

• A 1993 study compared a coal tar gel to ketoconazole gel against malassezia yeast. Results showed similar effectiveness between the two gels [6].
• A 1995 study tested coal tar against multiple malassezia yeast strains. Coal tar inhibition varied widely across strains (MIC 3-50 μm/ml). This was inferior to zinc pyrithione and selenium sulfide, but coal tar is used at higher concentrations in treatment [3].

So while coal tar may not be the most potent antifungal, high concentrations likely compensate for this.

Safety Profile

Thanks to over 150 years of use, the safety profile of topical coal tar is well-established:

• Multiple long-term studies over decades have not revealed any serious safety issues [7].
• Side effects are generally mild, including irritation, sun sensitivity, folliculitis, and contact allergy [8].

There were initially concerns about skin cancer risk from coal tar due to PAH content. However, well-designed epidemiology studies have not found clear evidence of increased skin or internal cancer risk [8, ].

So while not completely risk-free, coal tar appears relatively safe for topical use under medical supervision.

Comparison to Other Tars

Other tars beyond coal tar are also used medicinally, including:

• Pine tar: Derived from pine wood. Used primarily for the skin and respiratory conditions. Less research than coal tar [9].
• Sulfonated shale oil: Byproduct of shale oil industry. Used for psoriasis, eczema, and seborrheic dermatitis. Considered to have a better safety profile than coal tar [10].

While less studied, these alternative tars may offer comparable benefits to coal tar for seborrheic dermatitis treatment.

Drawbacks of Tars

The main drawbacks of coal tar and other tars are:

• Strong odor: Requires fragrances to mask smell, which can cause contact allergy [8].
• Staining: Leaves behind a dark color on skin and clothing [2].

These factors have likely reduced tar’s popularity compared to newer colorless and fragrance-free treatments.

Conclusion

Overall, while not a first-line treatment, coal tar remains a potential option for managing seborrheic dermatitis symptoms under medical guidance. Other tars may offer similar benefits with improved safety and tolerability. More research comparing tar preparations head-to-head could help clarify their risk/benefit profiles.