Hydro colloids are composed of gelatin, pectin and or car-boxy methyl cellulose, and serve as occlusive or semi-occlusive dressings. They are impermeable to water, bacteria and other contaminants but permeable to water vapor. They absorb wound exudes to form a hydrophilic gel.
They are not indicated for arterial/ osteopathic ulcers, infected or heavily exuding wounds because of risk of rewound maceration. Another down side of the treatment is their tendency to produce malodorous exudes, which can be mistaken for infection