Hydrocolloid (Colloid) Dressings

Definition and Etymology

"Colloid" comes from the Greek term for a two-phase system - a uniform dispersion of one phase of matter (unfilterable small particles) into another phase or matrix. Mutually attractive charges exist between the particles, contributing to the diffusible properties of colloids. This property accounts for the absorptive and expansive capacity of colloid gels, which function as a semipermeable membrane. Gel swelling occurs because the particle concentration of the gel is higher than that of the surrounding medium, drawing water from surroundings into the gel.

Composition and Structure

Hydrocolloid dressings (e.g., DuoDERM®) are available in sheet and paste forms and consist of two layers:

Layer	Content
Inner (adhesive) layer	Hydrophilic colloid base = mixture of pectin, karaya, guar, or carboxymethyl cellulose + adhesive containing polyisobutylene, styrene isoprene, or ethylene vinyl acetate
Outer layer	Thin semipermeable polyurethane film

When in contact with wound exudate, a gel forms, and as a unit, the dressing is semipermeable to water vapor and gases.

A second type is a synthetic, non-adherent, high-density plastic woven polymer (e.g., N-Terface®) through which fluid flows to an overlying dressing without adhering to new epithelium.

Hydrocolloid dressings were first employed as ostomy products and have since been adapted for wound care.

Mechanism of Action

Gel formation: Exudate is absorbed by the hydrocolloid, producing a yellowish-brown gelatinous mass - this is a normal finding (not pus), and the patient must be counselled about this.
Autolytic debridement: The accumulated exudate in a moist, semipermeable environment becomes a source of phagocytic cells and endogenous enzymes, promoting autolytic debridement that can be washed away with saline.
Angiogenesis stimulation: The semipermeable outer barrier has been shown to stimulate angiogenesis and increase the rate of healing.
Occlusion with absorbency: Combines benefits of both, unlike simple film dressings.

Advantages

Can be cut and conformed to wound shape (sheet form)
Waterproof - impermeable to water, oxygen, and CO2; popular "waterproof" dressing
Adhere directly - no secondary dressing required
Cushioning/pressure-relieving effect, especially at bony prominences (increases as dressing absorbs exudate)
Colloidal gel prevents adherence to wound base - atraumatic removal
Promotes autolytic debridement
Stimulates angiogenesis
Can be left in place for extended periods (less frequent changes)
No secondary dressing needed

Disadvantages

Maceration of peri-wound skin
Risk of irritant or allergic contact dermatitis (to adhesives)
Risk of forming excessive granulation tissue
End product (thick, yellow-brown, often foul-smelling gel) can resemble purulent discharge - must educate patient
Contraindicated in infected and/or highly exudative wounds (occlusion may enhance bacterial growth)

Indications (Wound Selection)

Hydrocolloid dressings are best suited for wounds based on depth and drainage as shown in the chart below:

Choice of dressing based on wound depth and exudate

Fig. 145.10 - Dermatology 2-Volume Set 5e

As seen in the chart:

Thin hydrocolloid - moderate wound depth, low-to-moderate drainage
Thick hydrocolloid - deeper wounds with moderate-to-high drainage
Hydrocolloid occupies a broad range but yields to alginate for very deep/highly exudative wounds

Clinical uses include:

Partial and full-thickness wounds
Pressure ulcers (especially at bony prominences - extra-thin hydrocolloid)
Venous and arterial leg ulcers
Post-debridement wound cover
Mastocytoma (hydrocolloid dressing under occlusion for symptom control)
Post-surgical wounds with minimal-to-moderate drainage

Comparison with Other Dressing Types

Dressing	Best for
Film	Shallow wound, minimal drainage
Gel/Hydrogel	Provides moisture to dry wounds, burn care
Hydrocolloid	Moderate depth, low-moderate drainage; maintains moisture
Alginate	Deep wounds with high exudate (hemostatic, absorptive)
Foam	Shallow-moderate depth with moderate drainage

Key Clinical Points

Hydrocolloid and hydrogel dressings form complex structures with water - fluid absorption occurs with particle swelling, aiding atraumatic removal
Hydrogel differs in being a cross-linked polymer with high water content, allowing high evaporation without compromising wound hydration (better for burns)
The foul-smelling yellow-brown gel on removal is not infection - patient education is essential
Occlusion is contraindicated in infected or highly exudative wounds

Sources: Dermatology 2-Volume Set 5e, p. 2968-2969 (Bolton 2025); Schwartz's Principles of Surgery 11th Ed, p. 335

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