Dermatologists have always been using tar products to treat skin diseases. For example, tar is an essential part of psoriasis therapy, either on its own or combined with ultraviolet light. Dermatologists also use it to treat eczema, though this is less common.
I’ve stopped recommending tar products in my practice, mostly because it’s OTC and I’ve forgotten about it. There is also an unproven concern that it can cause cancer, which is (understandably) a large deterrent. Furthermore, patients do not appreciate its pungent smell.
So when patient recently asked me about how my recommendation of tar products worked, I really didn’t have a clear answer. Thus, I did some research into the subject and learned some interesting things.
First, what makes up tar? Tar is a broad term that refers to organic plant matter that can occur naturally. You’ll find tar most commonly in pits, where you’ll will also find pitch and asphalt. One can also create tar-like products by dry heating coal to about 1200ºC. At this temperature, the coal melts into a thick liquid called crude coal tar.
Crude coal tar contains an estimated 10,000 high molecular weight hydrocarbons and aromatic (aka “odorous”) polycyclic hydrocarbons. These specific aromatic polycyclic hydrocarbons may help treat skin diseases.
Second, how do tar products interact with skin cells? Skin cells (keratinocytes) absorb and break down these aromatic polycyclic hydrocarbons using the same system that breaks down natural plant flavonoids. (Flavinoids are ubiquitous pigments in plants. Research indicates they have health benefits).
Furthermore, there is some research to suggest that the aromatic polycyclic hydrocarbons can help the barrier function in atopic dermatitis normalize. It may also help block the effects of inflammation in this particular disease.
In conclusion, I can now recommend tar products to patients with more confidence. It comes in useful for patients as an alternative to topical steroids, and for maintenance of stable chronic skin diseases.
From Feldman et al UpToDate
Wikipedia for “tar” and flavonoids