What is Para-Aminobenzoic Acid (PABA)?
Para-aminobenzoic acid (PABA) is a non-protein amino acid and an organic compound that is found in various natural sources and can also be produced synthetically for commercial use. It is a white, crystalline solid, though commercial samples may appear greyish. Its chemical formula is $C_7H_7NO_2$. PABA is an important intermediate in the synthesis of folate (Vitamin B9) by many types of bacteria, plants, and fungi. However, humans do not synthesize their own folate from PABA and must acquire it from dietary sources.
PABA's Classification as a 'Nonessential' Nutrient
For many years, PABA was classified as a B vitamin, sometimes referred to as Vitamin Bx or Vitamin B10. This classification has since been updated, and PABA is now considered a nonessential nutrient for humans. This is because the microbes living in the human gut microbiome, such as E. coli, are capable of synthesizing PABA from other compounds. While the body can produce some PABA, the amount is not sufficient for human needs, especially concerning its role as a precursor for folate production, which is a vital nutrient for DNA synthesis and repair.
Sources of Para-Aminobenzoic Acid
In addition to the amount produced by gut flora, PABA can be obtained from several dietary sources. These include:
- Brewer's yeast
- Whole grains
- Organ meats (such as liver and kidney)
- Mushrooms
- Spinach
- Eggs
- Milk
- Molasses
The History and Decline of PABA in Skincare
PABA is perhaps most famously known for its use as a chemical UV filter in sunscreens, a role it occupied starting in the 1940s. It was highly effective at absorbing ultraviolet B (UVB) radiation, which is responsible for causing sunburn. However, over time, significant safety concerns led to a sharp decline in its use in both topical and facial products.
Multiple studies and reports indicated that PABA could cause a high rate of allergic and photoallergic skin reactions in some individuals. Beyond skin sensitivity, research suggested PABA could increase the risk of cellular UV damage and potentially contribute to skin cancer under certain conditions, a finding that the FDA considered a serious concern. The FDA proposed that PABA is no longer generally recognized as safe and effective (GRASE) for sunscreen use, leading most manufacturers to phase it out. Safer, more stable, and less allergenic alternatives like zinc oxide and titanium dioxide have since become the standard in sunscreens.
Other Historical and Medical Uses
Beyond sun protection, PABA has been historically explored for other potential benefits, though many lack robust scientific evidence. Some of these include:
- Fibrotic Skin Disorders: The potassium salt of PABA, known as Potaba, has been used as a drug to treat conditions involving the hardening and thickening of skin and connective tissues, such as Peyronie's disease and scleroderma. However, the efficacy of PABA for these conditions is often debated and research results are conflicting.
- Premature Gray Hair: Early studies in the 1940s suggested that high doses of PABA could help repigment gray hair, but this effect has not been recently replicated or studied. The effect was also temporary, with hair reverting to its gray color upon cessation of use.
- Vitiligo: PABA was also investigated for vitiligo, a condition characterized by skin depigmentation. While some anecdotal reports exist, there is limited scientific evidence to support its effectiveness for this purpose.
For more detailed medical information on PABA, you can consult a reliable source such as the MedlinePlus medical encyclopedia.
Comparison of PABA with Modern Sunscreen Ingredients
| Feature | PABA (Para-aminobenzoic acid) | Zinc Oxide | Titanium Dioxide |
|---|---|---|---|
| Classification | Chemical UV absorber | Physical UV blocker | Physical UV blocker |
| Mechanism | Absorbs UVB radiation | Reflects and scatters UVA and UVB radiation | Reflects and scatters UVA and UVB radiation |
| Effectiveness | Primarily UVB protection | Broad-spectrum (UVA and UVB) | Broad-spectrum (UVA and UVB) |
| Safety Profile | Higher risk of allergic and photoallergic reactions | Very low risk of skin irritation; gentle for sensitive skin | Very low risk of skin irritation; gentle for sensitive skin |
| Status (FDA) | Not considered GRASE for sunscreen | Generally Recognized As Safe and Effective (GRASE) | Generally Recognized As Safe and Effective (GRASE) |
| Skincare Trend | Outdated; often avoided | Widely used; popular in mineral sunscreens | Widely used; popular in mineral sunscreens |
| Environmental Impact | Some concerns regarding derivatives | Considered safer for marine ecosystems | Considered safer for marine ecosystems |
Conclusion: The Place of Para-Aminobenzoic Acid in Modern Health
While the generic name for PABA is unequivocally para-aminobenzoic acid, its status in modern health and wellness has changed dramatically over the decades. Once considered a B vitamin and a staple ingredient in sunscreens, it is now classified as a nonessential nutrient for humans, whose bodies can produce it via gut bacteria. Its historical use in sunscreens was largely discontinued due to safety concerns, including a high rate of allergic reactions and potential photosensitivity. Better, safer, and more effective sunscreen alternatives have replaced it. Though it has some historical medical applications, current scientific consensus and research on its efficacy are often limited or conflicting. Today, consumers are more likely to find PABA or its derivatives in dietary supplements or specialized pharmaceutical compounds rather than mainstream skincare products. Understanding its full generic name, para-aminobenzoic acid, provides a more complete picture of this complex and evolving compound.
