An occlusive dressing is a medical dressing which seals a wound off from air and fluids as well as resisting penetration by viruses, bacteria, and other organisms. While no dressing can provide a completely perfect seal, occlusive dressings come close. Drugstores sometimes sell them and they are also available from medical supply catalogs. They are usually intended for hospital and clinical use and may be applied by a health care professional.
There are a number of reasons why a doctor might want to use an occlusive dressing as opposed to a more conventional dressing which allows a wound to breathe. One reason is to ensure that a topical ointment thoroughly penetrates a wound. The dressing seals the wound so that the ointment cannot evaporate and the dressing itself is minimally absorptive, forcing the ointment into the wound rather than sponging it up from the surface of the skin.
Another reason to use an occlusive dressing is in an allergy test. When testing suspected or potential allergens, an occlusive dressing can be applied to seal the wound off. This limits interference from allergens in air or fluids and also keeps the area of the wound in a constant state of exposure to the allergen, which will not be evaporated, absorbed by the bandage, or washed away by fluids. This can provide a more controlled environment for the testing.
Sucking chest wounds may also be treated with the use of an occlusive dressing, and such dressings may also be used for patients who have been partially eviscerated, to contain the bowels until the patient can be treated surgically. Combined with gauze, an occlusive dressing may also keep a wound moist. It can also be used with sponges or gauze soaked in materials like antibiotics and used in the treatment of certain types of wounds.
Such dressings usually come in the form of flat sheets which can be cut to size if necessary before being attached with adhesive tape. Taping on all sides of the bandage will create a snug seal, while leaving one side open can create a valve or flapper, which may be desired in some situations. Like other dressings, occlusive dressings need to be checked periodically and changed to reduce the risk of infection and other complications. For serious injuries, bandage changes may need to be performed by a nurse, doctor, or medical technician, while lesser injuries can be managed by the patient, following instructions from a medical provider.