Tar soap is a type of soap that contains natural tar, a substance derived from pine trees that has antiseptic and anti-inflammatory properties. Although tar soap is widely recognized by this name, it also goes by several different names and can be found under different product labels. Some of the most common synonyms for tar soap include pine tar soap, coal tar soap, and birch tar soap. These soaps can vary in their formula, scent, and benefits, but they all share the same key ingredient, tar. Tar soap is often used to treat a variety of skin conditions, such as psoriasis, eczema, and acne.