Hydrocolloid dressings are water-repellent dressings that consist of water-absorbing particles such as cellulose, pectins, or gelatins. The outer dressing consists of a semipermeable water-proof and germ-proof polyurethane foil that protects the wound. The main principle of a hydrocolloid dressing is the creation of pressure: the particles absorb wound fluid, swell, and turn into gel. This gel keeps the wound moist. The gel can absorb wound fluid until the hydrocolloids are saturated. This is the case when the dressing has the form of a bubble. Dead cells, excess fluid, and germs are removed with each dressing change.