Alginin is an edible natural gum obtained from kelp, mainly the giant kelp Macrocystis pyrifera. It absorbs water quickly, which makes it useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles. It is also used for waterproofing and fireproofing fabrics, for thickening drinks, ice cream and cosmetics, and as a detoxifier that can absorb poionous metals from the blood.

It is often used in the form of sodium alginate paste, or alginic acid.

Calcium alginate is used in burns dressings that promote healing and can be removed painlessly.