PABA is an essential nutrient for some bacteria and is sometimes called Vitamin Bx. However, PABA is not essential to human health, and is therefore not officially classified as a vitamin. Although humans lack the ability to synthesize folate from PABA, it is sometimes marketed as an essential nutrient under the promise that it can stimulate intestinal bacteria.
PABA is an intermediate in bacterial synthesis of folate. Sulfonamides are chemically similar to PABA, and their antibacterial activity is due to their ability to interfere with conversion of PABA to folate by dihydropteroate synthetase, and subsequent utilization, by bacteria.
The potassium salt is used as a drug against fibrotic skin disorders under the trade name POTABA. PABA is also occasionally used in pill form by sufferers of Irritable bowel syndrome to treat its associated gastrointestinal symptoms, and in nutritional epidemiological studies to assess the completeness of 24-hour urine collection for the determination of urinary sodium, potassium, or nitrogen levels.