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What do Kim Kardashian, LeAnn Rimes and Eli Roth all have in common? Other than taking over your Insta feed, these (and many other) celebs also have psoriasis.

Psoriasis is a highly visible skin condition that can be difficult to treat, especially when faced with an aisle full of over-the-counter “solutions” promising quick results for cheap.

One of the more promising OTC options, however, is tar soap, which has been a remedy for skin conditions since ancient times. Here’s a quick overview of just about everything you need to know about tar soap and psoriasis.

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Tar soap is what it sounds like: soap made with tar, a dark, thick liquid that’s derived from coal or the wood of various plants and coniferous trees (think pine and juniper).

Certain ingredients from both categories of tar are thought to help ease the symptoms of psoriasis.

Psoriasis, for any newbies in the room, is a chronic autoimmune condition that causes skin cells to build up in inflamed, red or silver, itchy patches. It can also lead to arthritis.

Besides potentially affecting your joints in the long run, psoriasis flare-ups are, simply put, uncomfortable and really the eff annoying.

Like most psoriasis treatments, tar soap can’t cure this condition. And because it’s made with tar, it can be harsh.

However, when used in appropriate amounts, it can reduce psoriasis symptoms and, in most cases, won’t lead to any unpleasant side effects (keep reading, we’ll explain those).

Keep in mind that more severe cases of psoriasis typically require more intense treatment, such as light therapy and oral medications. Your doctor can help you figure out the best plan for you.

There are two main varieties of tar soap to consider, both with similar benefits:

Coal tar

There’s a reason doctors have been prescribing this type of tar for psoriasis since the 1920s. While coal is composed of thousands of ingredients, scientists believe polycyclic aryl hydrocarbons, particularly carbazole, are behind its psoriasis-fighting abilities.

We know it sounds like another name for the Gate Keeper, but research has shown carbazole prevents cells from inflaming, which means fewer flare-ups and flakes.

Pine tar

Slightly less popular than coal tar, pine tar is thought to have a host of benefits. In addition to slowing the over-production of rough skin cells, research shows it relieves itching, fights inflammation, is antibacterial, and antifungal.

Tough to say, since tar soaps and other tar products come in different formulations. Most commonly these products are sold with 1–10 percent coal or pine tar.

You’ll need to chat with your doctor and do some experimentation to find the right fit, but they can be bought over-the-counter as:

  • Bar soap. Best for treating psoriasis over large areas of your body. You use it a lot like regular bar soap, letting it sit on your skin before rinsing off for the best results.
  • Cream. Good for psoriasis on parts of your body other than your scalp. Generally, you apply a small amount of cream to the affected areas on your skin, one to four times per day for several weeks. Always check the product directions before applying.
  • Shampoo. Ideal for scalp psoriasis. You can use tar soap shampoo a lot like your regular shampoo, scrubbing into your wet scalp in the shower and then letting it sit before rinsing off.
  • Oil. Usually more concentrated than creams and shampoos. Tar oil is very quickly absorbed into the skin and is best suited for aggressive cases of psoriasis.

Stronger concentrations of tar soap, for very serious cases of psoriasis, are sold by prescription only. Again, your doc will know what’s best and can help you craft the right treatment plan.

Shop coal tar soap and pine tar soap.

Just like you need to wait for that delicious takeout order, it might take a minute before you see results from tar soap. (All good things…) Most see clearer skin within a few weeks.

Users of tar products have reported a reduction in the thickness of skin cell (also called plaque) buildup. Tar soap has also been shown to give skin a smoother and less inflamed appearance. It can also reduce itching. Sweet relief!

Tar products are meant for short-term control over psoriasis flare-ups. Because tar is a powerful ingredient, you should not use tar soaps and other tar products more than a few times per week for up to several weeks.

Beware if you have sensitive skin, as tar products can worsen irritation. If this is the case for you, you may want to first try a very diluted product with a lower percentage of tar.

Tar soaps and other products tend to be messy, and can lighten skin or stain clothing and bedding.

Also, to be honest, they kind of stink. Not like a skunk or anything, just prepare yourself to emit a blacktop-esque aroma (sudden urges to play hopscotch and kickball may follow).

Tar products are generally considered a safe treatment for psoriasis, but women who are pregnant or breastfeeding are advised not to use them.

You should also avoid direct sunlight for 24 hours after using tar-based psoriasis products, as they may make you more susceptible to sunburn.

It has been argued that coal tar products can cause cancer because it was found to cause cancer in occupational exposure to coal tar (for example miners, asphalt workers, or chimney sweeps).

However, a 2010 study seemed to put the debate to rest. An increased risk of cancer with the use of coal tar soap was not found. It also noted that coal tar soap could be considered a safe treatment for psoriasis and eczema.

Be aware that showering and washing may actually remove moisture from your skin. In order to prevent that from happening when you use tar soaps, be sure to:

  • Use lukewarm, not hot, water when you shower.
  • Limit your shower or bath time to 15 minutes or less, once per day.
  • Avoid vigorous scrubbing with a washcloth or loofah.

Tar is only one ingredient that is known to help ease psoriasis symptoms. If tar is not your thing, here’s a list of other ingredients to look for in soaps and other psoriasis products available over the counter and by prescription:

  • Aloe vera. Soaps, creams and oils containing aloe vera have been shown to reduce the symptoms of psoriasis. They have a moisturizing, healing effect on skin.
  • Calcipotriene. A synthetic form of vitamin D3 that is applied to the scalp before bed and then washed off in the morning.
  • Corticosteroids. The most-prescribed treatment for scalp psoriasis and is most often applied directly to skin as a cream.
  • Mahonia aquifolium. Also known as Oregon grape, an herb found in many psoriasis soaps and products. Research suggests it is an effective treatment for mild to moderate psoriasis.
  • Oatmeal baths and oat soaps. Used by many people with psoriasis, who swear they can help relieve itchy skin and redness. If you’ve ever had chicken pox, odds are your parents dunked you in a tub of this stuff.
  • Salicylic acid. A medication that helps dissolve surface skin cells, and also frequently used to treat acne. You can get a stronger version of salicylic acid soaps and other products with a doctor’s prescription.
  • Tazarotene. A medication that you leave on overnight and wash off in the morning to clear up psoriasis flare-ups.
  • Tea tree essential oil. Adds antibacterial, anti-inflammatory, antiviral, and antifungal properties to soaps and other products, and can reduce inflammation associated with psoriasis.

If you’re trying over-the-counter soaps or other psoriasis products, pay close attention to how they affect your skin. If your psoriasis worsens, stop using these treatments right away and call your doctor.

Treating your psoriasis will take some trial and error to determine what works best for you.

Over-the-counter tar soaps and products are just one treatment option that is helpful to many people with psoriasis. If you have a mild to moderate case, tar may be for you.

If tar soaps and other products aren’t helping, don’t give up! There are plenty of options out there to help you find relief. Keep your doctor in the loop and remember that finding the right treatment can take time.