PABA, or para-aminobenzoic acid, is a naturally occurring substance used in sunscreen products. While the U.S. Food and Drug Administration vouches for the safety of PABA as a sunscreen ingredient, sunscreens with PABA cause allergic reactions in some people, and limited research suggests PABA may produce cancerous changes in skin cells. There is not strong evidence supporting oral use of PABA, and taking large oral doses of PABA can result in life-threatening consequences.
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Safety of PABA in Sunscreen
PABA was one of the first commonly used chemical sunscreen ingredients. Applied topically, PABA protects the skin from ultraviolet B, or UVB, rays, thereby protecting the skin from sunburn, sun damage and skin cancer. However, due to high incidence of allergic reactions to PABA, it was eventually removed from most sunscreen formulations. Additionally, while there is not conclusive or extensive evidence indicating PABA as a carcinogen, research published in the early 1980s, including a study published in "The Journal of Investigative Dermatology" in 1982, suggested topical PABA may cause mutated skin cells in lab rats, which further contributed to PABA's negative reputation. Nevertheless, PABA today remains an FDA-approved sunscreen ingredient and many sunscreens now use less-irritating PABA esters such as padimate A.
PABA is also sometimes used orally, as a dietary supplement, although there is scant evidence to indicate oral PABA as an effective treatment for any health condition. Despite the lack of research supporting the usefulness of taking PABA internally, PABA supplements are sometimes suggested as an alternative treatment for Peyronie's disease, scleroderma, vitiligo and male infertility. When taken orally, PABA is probably safe in dosages up to 400 mg, although the same is not true for higher doses, which may result in serious side effects, including liver failure, according to Natural and Alternative Treatments. The safety of oral PABA use for young children, pregnant or nursing women, or those with serious kidney or liver disease is not known, and PABA may also interact with certain medications, inclding sulfa antibiotics, says NAT.
Allergic Reactions and Overdose
Both oral and topical PABA use may result in allergic reactions, and PABA overdose may occur if you take more the recommended amount of PABA. However, most negative reactions to PABA are due to allergic reactions, not overdose, according to MedlinePlus. Symptoms of an allergic reaction or overdose to PABA include a skin rash, dizziness, diarrhea, nausea and vomiting. More serious PABA reactions include shortness of breath, slowed breathing, stupor, coma and liver failure. According to MedlinePlus, if you have a PABA reaction from topical exposure to the skin or eyes, it's important to flush with lots of water for 15 minutes, and if you're having a reaction from ingesting the chemical, you should drink water or milk immediately unless otherwise instructed by a health care professional.
PABA Alternatives and Considerations
Due to public health concerns about PABA, many sunscreen formulations are now PABA-free. Moreover, due to safety concerns about synthetic chemicals still commonly used in sunscreens, including parabens, oxybenzone, and retinyl palmitate, there is a growing market for "all-natural" sunscreens. Natural sunscreens typically use mineral ingredients such as zinc oxide and titanium dioxide, which act as physical, rather than chemical, barriers to UV rays. Zinc oxide and titanium dioxide also provide full-spectrum UV coverage, which means they protect you from damaging UVA rays as well as the UVB rays blocked by sunscreens like PABA. According to the American Melanoma Foundation, your skin is best protected from the harmful effects of UV radiation when you use a full-spectrum sunscreen with an SPF of 15 or higher.