A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Bacteria that live in the intestines need PABA to survive. PABA is found in grains and foods from animals. It is being studied as a radiosensitizer (a substance that makes tumor cells more sensitive to radiation therapy) and in the treatment of certain skin disorders. Also called aminobenzoic acid and para-aminobenzoic acid.