Silver has broad-spectrum antimicrobial activity.¹⁰ Resistance is much less likely than with antibiotics as, like other antiseptics, silver acts at multiple sites on and in target cells.¹⁶

Silver sulfadiazine became a standard treatment for burns more than 30 years ago. Since then, silver has become established as a component in wound dressings, including first aid plasters.

Traditionally this has been as the metal (sometimes in nanocrystalline format) which ionises on contact with the wound fluids, in organic complexes (such as or as silver alginate), or as an inorganic salt such as silver oxide, silver phosphate or silver chloride.¹⁶

The reactive Ag+ ion is the key factor in its antimicrobial activity, disrupting the biofilm.¹⁶ However, Crawford Healthcare has introduced a more reactive ion, Ag3+, into dressings. It claims its KerraContact AG3+ with Oxysalt Technology has improved activity against biofilms, breaking down the biofilm in 30 minutes and suppressing bacterial growth for a week.¹⁷

There is some evidence suggesting silver nitrate, nanocrystalline silver, and some silver-containing dressings may also have anti-inflammatory effects and encourage blood vessel formation (neovascularisation) although the clinical relevance is not yet understood.¹⁶