PABA (para-aminobenzoic acid) is not technically “banned” in a blanket sense, but the FDA has proposed classifying it as not safe and effective for use in sunscreens. This means it can no longer be used as an active ingredient in over-the-counter sunscreen products sold in the United States. The decision came down to a combination of allergic reactions, DNA damage from its photochemistry, and the availability of safer alternatives that made PABA’s risks outweigh its benefits.
What PABA Actually Does
PABA was one of the first UV-filtering chemicals used in sunscreens, absorbing radiation in the UVB range with peak absorption at 286 nanometers. It was effective at preventing sunburn, which is primarily caused by UVB rays. At its peak, sunscreen formulations could contain up to 15% PABA.
The problem is that PABA only blocks UVB. It does nothing against UVA rays, which penetrate deeper into the skin and contribute to premature aging and skin cancer. As scientists learned more about UVA damage through the 1980s and 1990s, PABA’s narrow protection became a significant limitation. But the real reasons for its removal go beyond its limited spectrum.
The FDA’s Safety Ruling
In a 2019 proposed rule, the FDA classified PABA as Category II for sunscreen use, meaning the evidence shows it is not generally recognized as safe and effective (GRASE). Only two sunscreen ingredients out of 16 previously approved ones received this classification: PABA and trolamine salicylate. Both were singled out specifically because of safety concerns, not just insufficient data.
For context, the FDA placed 12 other common sunscreen ingredients (including oxybenzone, avobenzone, and octinoxate) in a separate category where more data was needed before a safety determination could be made. Two ingredients, zinc oxide and titanium dioxide, were the only ones classified as safe and effective. PABA’s placement in the “not safe” category rather than the “needs more data” category reflects how strong the evidence against it had become.
Allergic and Photoallergic Reactions
The most well-documented problem with PABA is its tendency to cause skin reactions. The FDA cited “significant rates of allergic and photoallergic skin reactions” as a primary reason for its proposed removal. Photoallergic reactions are particularly concerning because they only appear when the chemical is activated by sunlight, which is exactly when you’d be wearing sunscreen. People would apply PABA-containing sunscreen, go outside, and develop rashes, itching, or blistering on the areas where the product was applied.
Making matters worse, PABA causes cross-sensitization with structurally similar compounds. Once your immune system reacts to PABA, it can also start reacting to related chemicals found in common medications. The FDA specifically flagged this as a risk, noting it “may lead to allergies to commonly used medications.” This means a sunscreen ingredient could potentially trigger drug allergies that persist long after you stop using the product.
DNA Damage and Photochemical Problems
Beyond skin reactions, PABA has troubling photochemical properties. When exposed to UV light, it doesn’t just passively absorb the radiation. It generates reactive molecules that can damage cells. In vitro studies dating back to 1982 showed that PABA can trigger the formation of thymine dimers in human cells. Thymine dimers are a specific type of DNA damage that is also caused by direct UV exposure, which is the very thing sunscreen is supposed to prevent.
PABA was found to be the most efficient producer of singlet oxygen (a reactive molecule that damages tissue) among sunscreens tested under steady-state UV exposure. It also forms free radical byproducts and binds directly to DNA in solution, creating additional photoproducts. In short, the chemical meant to protect skin from UV damage was simultaneously creating its own form of cellular damage when activated by light.
What About Padimate O?
Padimate O (also called octyl dimethyl PABA) is a derivative of PABA that was developed to address some of its parent compound’s problems. It absorbs UVB at a slightly different peak wavelength of 309 nanometers and is less water-soluble, which reduces some skin irritation issues. It remains permitted in sunscreens at concentrations up to 8%, though the FDA has placed it in the “needs more data” category rather than clearing it as safe.
Padimate O carries its own concerns. Research has shown that when activated by sunlight, it directly damages DNA. In one study, skin cells exposed to sunlight while treated with a sunscreen containing Padimate O showed at least 75 times more DNA strand breaks than cells treated with a sunscreen without it. Lab studies have also found it can interact with estrogen receptors in cell cultures, though animal studies did not confirm estrogenic effects in living organisms. It has not been classified as a carcinogen by any major regulatory body.
PABA in Supplements and Food
The FDA’s action applies specifically to PABA as a sunscreen ingredient. PABA is still available as an oral dietary supplement, sometimes marketed under the name “vitamin Bx,” though it is not actually a vitamin. It occurs naturally in brewer’s yeast, liver, mushrooms, spinach, whole grains, and molasses.
Oral PABA is not without risks. Allergic reactions are the most common problem and can cause rash, nausea, vomiting, diarrhea, and dizziness. In more serious cases, symptoms can include fever, liver failure, slowed breathing, and loss of consciousness. These severe outcomes are rare but documented. If you see PABA sold as a supplement, it has not gone through the same safety review process that led to its removal from sunscreens.
Why Manufacturers Stopped Using It
Although the FDA’s formal proposed rule came in 2019, sunscreen manufacturers had already abandoned PABA years earlier. The FDA itself noted that neither PABA nor trolamine salicylate “is used in marketed sunscreens any longer” at the time of its ruling. The combination of consumer complaints about skin reactions, negative publicity from DNA damage studies in the 1980s and 1990s, and the development of better UV filters made PABA commercially unviable long before regulators caught up. The 2019 action was essentially the FDA formalizing what the market had already decided.