Medical dressings are made from a wide range of materials, from simple cotton gauze to advanced polymers and biological compounds derived from seaweed or animal tissue. The specific materials depend on the type of dressing, but most share a common goal: protecting the wound, managing moisture, and supporting the body’s natural healing process. Here’s what goes into each major category.
Traditional Gauze and Non-Woven Dressings
The simplest wound dressings are woven or non-woven fabric pads. Their composition typically includes cotton, polyester, or rayon, either alone or blended together. Woven gauze has an open, grid-like weave that allows air to reach the wound, while non-woven versions are made by pressing or bonding fibers together rather than weaving them. These basic materials are inexpensive and widely available, though they don’t actively manage moisture the way more advanced dressings do.
Foam Dressings
Foam dressings are most commonly made of soft polyurethane, a synthetic polymer structured with two phases: a solid polymer framework and tiny air-filled pockets. Those pockets give the foam its cushioning and absorbent qualities. The surface of the foam is often treated to become water-attracting, creating a non-stick layer that lets wound fluid pass through into the foam’s body without adhering to the wound itself.
The size and shape of the air pockets matter. Pore diameters in some foam dressings range from 25 to 75 micrometers, while others span a much wider range of 32 to 1,000 micrometers. Smaller, more uniform pores generally provide more consistent absorption. The walls between pores (called struts) also vary in thickness, from roughly 70 micrometers in small-pored foams up to 300 micrometers in foams with large pores. These structural details determine how well a dressing absorbs fluid, holds its shape under movement, and cushions the wound.
Hydrocolloid and Hydrogel Dressings
Hydrocolloid dressings contain gel-forming polymers that absorb wound fluid and create a moist healing environment. A key ingredient in many of these is carboxymethylcellulose, a compound derived from plant fiber. It’s biocompatible, biodegradable, and inexpensive, which makes it a go-to material for this category. Some formulations combine it with gelatin, a protein sourced from animal tissue, which forms a cross-linked network that gives the dressing its gel-like consistency. A small amount of citric acid is often used as a crosslinking agent to bind the polymers together into a stable structure.
Hydrogel dressings work on a similar principle but contain a higher percentage of water. They’re especially useful for dry wounds because they donate moisture rather than just absorbing it. Both types keep the wound surface from drying out, which supports cell growth and tissue repair.
Alginate Dressings
Alginate dressings are made from a natural polymer extracted from brown seaweed, including kelps. The alginate molecule is built from two sugar-based building blocks (mannuronic acid and guluronic acid) arranged in chains. When these chains come into contact with calcium ions, a strong chemical bond forms between them, creating a three-dimensional gel that’s insoluble in water and won’t break down with heat.
This reaction is what makes alginate dressings so effective at absorbing large amounts of wound fluid. As the dressing absorbs moisture, it transforms from a fibrous pad into a soft gel that conforms to the wound’s shape. Calcium alginate is the most common form used in commercial products. Some alginate dressings are also impregnated with additives like manuka honey for additional antimicrobial benefit.
Transparent Film Dressings
Thin, see-through dressings are typically made from semi-permeable polyurethane membranes. “Semi-permeable” means the film allows water vapor and oxygen to pass through but blocks bacteria and liquid water. This lets the wound breathe without being exposed to outside contaminants. These films are flexible and conformable, making them a common choice for superficial wounds, IV sites, and as a secondary layer over other dressings. One experimental polyurethane film showed a water vapor transmission rate of 390 grams per square meter per day, giving a sense of how actively these thin materials manage moisture.
Antimicrobial Dressings
When infection is a concern, dressings may contain an active antimicrobial ingredient layered into or onto the base material. The three most common are silver, honey, and iodine.
- Silver is a broad-spectrum antimicrobial that works by damaging bacterial DNA, cell walls, and the enzymes bacteria need to survive. It’s incorporated into many dressing types, including foams, alginates, hydrocolloids, gels, gauze, and powders. Silver-impregnated dressings release silver ions slowly, which reduces bacterial load while limiting damage to healthy tissue. A single silver dressing can provide 3 to 7 days of antimicrobial protection.
- Manuka honey works through osmotic effects, drawing fluid from deeper tissue layers and helping remove dead tissue. It also has anti-inflammatory properties and stimulates new blood vessel formation. MediHoney dressings, one of the most studied brands, have been shown to speed bacterial clearance in diabetic foot ulcers and reduce the need for antibiotics.
- Metal oxide nanoparticles such as zinc oxide, iron oxide, and titanium dioxide represent newer antimicrobial agents being incorporated into dressing materials for sustained antibacterial activity.
Collagen Dressings
Collagen dressings are made from the same structural protein found in skin, bones, and connective tissue. Most commercial collagen dressings use type I collagen sourced from cow skin and bone, which is the most affordable and abundant option. Porcine (pig) skin is another common source. More specialized options include collagen derived from marine creatures like fish, jellyfish, sponges, and squid, as well as recombinant human collagen produced in yeast or plant cells without any animal components.
These dressings work by providing a scaffold that the body’s own cells can migrate into and build on, essentially giving the wound a structural template for new tissue growth. Marine and recombinant sources are growing in popularity because they eliminate the risk of animal-borne disease transmission.
The Adhesive Layer
Most dressings that stick directly to the skin use one of three types of pressure-sensitive adhesive: acrylic, silicone, or polyurethane. Each behaves like a thick liquid when you press the dressing onto skin, spreading into the tiny irregularities created by pores, wrinkles, and hair. Once the pressure is released, the adhesive firms up into an elastic solid that moves with the skin.
Silicone adhesives are popular in wound care because they bond well to skin, peel off gently, and are highly biocompatible. Acrylic adhesives naturally function as viscous liquids at room temperature due to the flexibility in their chemical backbone, which helps them form a strong initial bond. Polyurethane adhesives have an elastic stiffness very close to that of soft tissue (about 1 to 2 megapascals compared to tissue’s 1 megapascal), which means the dressing flexes and stretches in sync with your body rather than pulling against it.
Multi-Layer Composite Dressings
Advanced dressings often combine several of these materials into distinct layers, each with a specific job. A typical three-layer design includes a bottom contact layer that touches the wound and absorbs fluid, a middle active layer containing antimicrobial or healing agents, and a top barrier layer that blocks bacteria and prevents fluid from leaking out.
In one research example, the bottom layer was made of water-attracting nanofibers (roughly 94 nanometers in diameter) designed to absorb wound fluid and promote cell growth. The middle layer was a 3D-printed blend of alginate and zinc oxide nanoparticles for antibacterial protection. The top layer was made of water-repelling polycaprolactone nanofibers to prevent bacteria and external fluids from reaching the wound. This layered approach mimics the natural structure of skin itself, with each layer serving a function analogous to a different skin layer.