Para-aminobenzoic acid (PABA) has been traditionally used as a dietary supplement for hair health, largely based on anecdotal reports and early studies from the mid-20th century. During the 1940s and 1950s, some small and poorly controlled studies suggested that PABA might help restore hair color in cases of premature graying and possibly support hair growth. However, these findings have not been consistently replicated in more rigorous, modern clinical trials. There is no strong scientific consensus or robust body of evidence to confirm that PABA supplementation has a significant or reliable effect on hair growth, hair loss prevention, or hair pigmentation in the general population.

The mechanism by which PABA was thought to work involves its role as a precursor in the synthesis of folate by bacteria, but this does not directly translate to benefits in human hair health. Despite its historical use in hair products and supplements, major health organizations do not endorse PABA for hair-related purposes, and it is not considered an essential nutrient for humans. Adverse effects, such as skin rashes and, rarely, liver toxicity, have also been reported with PABA supplementation at higher doses.

In summary, while PABA has a history of traditional use for supporting the hair body system, scientific evidence justifying its effectiveness is weak and not sufficient to support its widespread use for this purpose.