Ester-C is a patented ingredient that provides powerful immune system support.* It is quickly absorbed and gentle on your stomach.* Ester-C also contains C-Sorb. Ester-C along with C-Sorb and naturally occurring metabolites, works synergistically to enhance the absorption and retention of Vitamin C in your body. In a clinical study, white blood cell levels of Vitamin C were elevated in subjects receiving Ester-C when measured 24 hours after initial dose. Ester-C gives you powerful immune system support at the cellular level for up to 24 hours - to help keep you healthy.* Ester-C is non-acidic. That means it's stomach-friendly. Ester-C is gentle on your stomach so you can feel comfortable taking it every day. Suitable for vegetarians. Free of: yeast, wheat, milk or milk derivatives, lactose, sugar, preservatives, soy, artificial color, artificial flavor, sodium (less than 5 mg per serving).