PABA is an organic compound that bacteria and plants use to make folate. Human cells lack that pathway, so we do not need it. Decades ago it was labeled vitamin Bx, but that designation was dropped once researchers confirmed it is not a vitamin for people.
Topically, PABA absorbs UVB light, which made it a staple in older sunscreen formulas. Orally, doses have been tested for skin hardening conditions and Peyronies disease, though the clinical evidence is thin. Some people also take it hoping to improve hair texture or skin appearance.
Capsules, tablets, and creams are common forms. To avoid stomach upset, oral doses are best taken with food. High intake can trigger nausea, vomiting, or skin rashes. Watch out for interactions with sulfonamide antibiotics. Safety in pregnancy, breastfeeding, and for those with kidney or liver trouble has not been pinned down, so medical guidance is wise.