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PABA

Para-aminobenzoic acid was once marketed as "vitamin Bx" — it is not a vitamin for humans, and the grey-hair and vitiligo claims that sell it come from uncontrolled 1940s reports. Its one real use, high-dose potassium para-aminobenzoate for Peyronie's disease, is a prescription drug in parts of Europe.

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What the science says

  • Restores grey hair to its natural color Limited evidence

    This claim traces to uncontrolled case series from the 1940s in which large PABA doses were said to darken grey hair in some subjects. No controlled trial has ever confirmed it, and the effect — where reported at all — reversed on stopping. Human hair greying is driven by melanocyte stem-cell depletion, which PABA has no established mechanism to reverse.

  • Slows plaque progression in Peyronie's disease Moderate evidence

    A prospective, placebo-controlled randomized trial of potassium para-aminobenzoate (POTABA) 12 g/day for 12 months in 103 men found significantly less plaque-size progression and a lower rate of penile-curvature deterioration versus placebo, though it did not reduce curvature that was already established. This is a drug-level dose under medical supervision, not a supplement use, and POTABA is prescription-only in Germany and several other countries.

  • A required vitamin humans need to supplement Limited evidence

    PABA is a substrate bacteria use to synthesize folate; humans absorb folate directly and have no PABA requirement, no deficiency syndrome and no established RDA. Because of this role it directly antagonizes sulfonamide antibiotics, which work by blocking bacterial PABA utilization.

Dosage & safety

Studied doseSupplements typically supply 100-500 mg/day, a dose with no demonstrated benefit for any condition. The Peyronie's protocol is potassium para-aminobenzoate 12 g/day in four divided doses for 12 months — 24 to 120 times the typical supplement dose, taken under urological supervision, and poorly tolerated by many patients.
SafetyDoses above roughly 8-12 g/day cause nausea, anorexia, rash and fever, and are the main reason patients drop out of Peyronie's protocols; hepatotoxicity and symptomatic hypoglycemia have been reported at high intakes. PABA antagonizes sulfonamide antibiotics and should not be combined with them; it may also interact with dapsone and methotrexate. Do not use in pregnancy or in children. Topical PABA was one of the classic sunscreen contact and photocontact allergens and was withdrawn from sunscreens — the FDA does not consider it generally recognized as safe and effective for that use — so people with a known PABA sunscreen allergy should avoid the oral form. Avoid in kidney or liver disease.

How to take it

TimingDivided doses across the day, as in the high-dose Peyronie's protocol.
With food?With food, which limits the nausea and anorexia that end most high-dose courses.
Worth knowingIf you have ever reacted to an old PABA sunscreen, avoid the oral form too — it was one of the classic contact and photocontact allergens.

Interactions

With medications

  • sulfonamide antibiotics (co-trimoxazole, sulfamethoxazole)

    PABA directly antagonises how sulfonamides work and can make treatment fail. do not take them together

  • dapsone

    The same antagonism applies to sulfones. avoid combining

  • methotrexate

    PABA can displace methotrexate from plasma proteins and increase its toxicity. do not combine

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does PABA reverse grey hair?

No controlled trial has ever confirmed that PABA restores grey hair; the claim traces to uncontrolled case series from the 1940s, and where an effect was reported it reversed on stopping (limited evidence). PABA has no established mechanism to reverse the melanocyte stem-cell depletion that drives greying.

Is PABA a vitamin?

PABA (para-aminobenzoic acid) is not a vitamin for humans: bacteria use it to make folate, but humans absorb folate directly and have no PABA requirement, no deficiency syndrome and no RDA. The old "vitamin Bx" label is marketing, not biology.

Does PABA help Peyronie's disease?

High-dose potassium para-aminobenzoate (POTABA) has moderate evidence in Peyronie's disease: 12 g/day for 12 months slowed plaque progression in a placebo-controlled trial of 103 men, though it did not reduce curvature already present. That is a prescription-level dose under urological supervision, far above the 100-500 mg in PABA supplements.

Can I take PABA with antibiotics?

Do not take PABA with sulfonamide antibiotics such as co-trimoxazole or sulfamethoxazole, because it directly antagonizes how they work and can make treatment fail. PABA should also not be combined with dapsone or methotrexate.

Scientific references

Where to buy

Swanson Vitamins, PABA, 500 mg, 120 Capsules

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