Other names it goes by? Mexoryl SL, terephthalylidene dicamphor sulfonic acid What's it used in? Sunscreen of SPF 15 and above and facial moisturisers. What does it do? Terephthalylidene absorbs ultraviolet light. Any controversy? It's restricted for use in cosmetics, with a maximum concentration of 10 per cent. It can cause dermatitis, acne, eczema, itching, redness and dry skin.