INGREDIENT · UVA FILTER
Ecamsule in sunscreen: the UVA filter and what trials show
Ecamsule is a UVA filter that is easy to miss on a label because of its long chemical name. Its absorption has been measured in only a few small studies, and there is one trial in people with sun allergy.
You may see it written as
- Terephthalylidene Dicamphor Sulfonic Acid
What ecamsule is
Ecamsule is the short name for terephthalylidene dicamphor sulfonic acid.1 A 2007 review says older US broad-spectrum sunscreens, which relied on mineral filters or avobenzone, degraded under UV exposure. It describes ecamsule as a novel ultraviolet A filter with efficient UVA coverage, better photostability and enhanced water resistance, reports that sunscreens with it were widely used in Europe and Canada, and says the US Food and Drug Administration approved it in July 2006.2
In 2015 the FDA tentatively found the available data insufficient to add ecamsule to its general over-the-counter sunscreen rules,1 and it is not on the list of filters in those rules as amended in 2026.3
How much gets into the body
In a study in volunteers, a sunscreen emulsion containing radiolabelled ecamsule was left on the skin for four hours. Between 89% and 94% of the radioactivity was recovered in wash-off samples, urine held at most 0.014% of the applied dose, and none was found in blood or faeces. The authors conclude the systemically absorbed dose is less than 0.1%, and that human exposure is negligible. In isolated skin, 0.16% of the dose was found in the dermis and receptor fluid after 24 hours.4
This is one study of one formulation applied for four hours, and its first author worked in research at a cosmetics company.4
A 2019 FDA trial applied sunscreens under maximal-use conditions. With a sunscreen cream containing ecamsule, the peak blood level averaged 1.5 ng/mL, above the 0.5 ng/mL level below which the FDA may waive some further safety studies. Only six people used that cream.5
The sun-allergy trial
In a 2009 double-blind trial, 144 people prone to polymorphous light eruption (a sun-triggered rash) used a sunscreen mix of 3% ecamsule, 10% octocrylene, 2% avobenzone and 5% titanium dioxide on one side of the body, and a version without ecamsule, or without avobenzone, on the other. The full mix was the better one more often: 56% against 11% compared with the version without ecamsule, and 36% against 16% compared with the version without avobenzone.6
Because all the filters were in a mix, the trial cannot say what ecamsule alone does. It shows that a UVA-covering combination worked better than one missing a UVA filter, in a group with a sun-triggered condition.
Using ecamsule with other products
The trial above tested ecamsule in one sunscreen with avobenzone, octocrylene and titanium dioxide.6 That is one product, not layered products.
Ecamsule in pregnancy and breastfeeding
We found no pregnancy- or lactation-specific evidence for this ingredient.
Evidence on cosmetic products in pregnancy is limited overall, so ask your doctor or midwife about the specific product you use.7
What you will see on the label
On a label, look for Terephthalylidene Dicamphor Sulfonic Acid. Snifff shows it as Low risk. For the rest of the formula, see what the score means and how to read the list.
As Snifff shows itTerephthalylidene Dicamphor Sulfonic Acid
Pregnancy and nursing
We found no pregnancy- or lactation-specific evidence for this ingredient.
Wording as it appears in the extension, which can change between releases.
A FEW MORE ANSWERS
Common questions about ecamsule
Is ecamsule absorbed into the body?
In a volunteer study, the systemically absorbed dose was estimated at less than 0.1% of the applied dose.4 Under maximal-use conditions, a 2019 FDA trial measured it in blood above the agency’s 0.5 ng/mL threshold.5
Is ecamsule better than avobenzone?
A 2007 review says older US sunscreens with avobenzone degraded under UV exposure, and describes ecamsule as more photostable.2 No trial we found compared them head to head.
What is the name on the label?
Look for Terephthalylidene Dicamphor Sulfonic Acid on the ingredient list. FDA notices call the same filter ecamsule.1
Is ecamsule safe in pregnancy?
Snifff found no pregnancy-specific evidence for Ecamsule. Ask your doctor or midwife about the product you use.
WHERE THIS COMES FROM
Sources
- Over-the-counter sunscreen drug products: regulatory status of ecamsule (proposed sunscreen order)US Food and Drug Administration, Federal Register 80(37) · 2015
- Mexoryl: a review of an ultraviolet A filterD'Souza G, Evans GRD · Plastic and Reconstructive Surgery · 2007
- Final Administrative Order OTC000039: amending Over-the-Counter Monograph M020, Sunscreen Drug Products for Over-the-Counter Human Use (issued 10 June 2026)US Food and Drug Administration · 2026
- Percutaneous absorption of Mexoryl SX in human volunteers: comparison with in vitro dataBenech-Kieffer F, Meuling WJ, Leclerc C, Roza L, Leclaire J, Nohynek G · Skin Pharmacology and Applied Skin Physiology · 2003
- Effect of sunscreen application under maximal use conditions on plasma concentration of sunscreen active ingredients: a randomized clinical trialMatta MK, et al. · JAMA · 2019
- A new ecamsule-containing SPF 40 sunscreen cream for the prevention of polymorphous light eruption: a double-blind, randomized, controlled study in maximized outdoor conditionsDeLeo VA, Clark S, Fowler J, Poncet M, Loesche C, Soto P · Cutis · 2009
- Cosmetic dermatology in pregnancy and lactation: a risk-benefit framework for clinical practiceKovacs T, et al. · International Journal of Dermatology · 2026
This page explains an ingredient. It is not medical advice, and it is not an assessment of any product. If you are pregnant, breastfeeding, or have a skin condition, ask your doctor or pharmacist.