Para-aminobenzoic acid (PABA) is best known as the active ingredient in sunblock. This use of PABA is not really medicinal: like a pair of sunglasses, PABA physically blocks ultraviolet rays when it is applied to the skin.

There are, however, some proposed medicinal uses of oral PABA supplements. PABA is sometimes suggested as a treatment for various diseases of the skin and connective tissue, as well as for male infertility. However, most of the clinical data on PABA comes from very old studies, some from the early 1940s.

PABA is not believed to be an essential nutrient. Nonetheless, it is found in foods, mainly in grains and meat. Small amounts of PABA are usually present in B vitamin supplements as well as in some multiple vitamins.