Acetic Acid and Dakin’s Solution: Are They Proper Wound Care Today?

Published on January 15, 2020 by Bill Richlen, PT, WCC, DWC

We must ensure we provide wound care treatments based on solid medical rationale and science or clinical evidence. 

This applies to wound care clinicians, especially certified wound care clinicians, and includes all aspects of wound care — even applying Dakin’s solution and acetic acid.

Unfortunately, in my 25 years of wound care experience, I still see many practices that do not meet those criteria. I am guilty too.

Back in the early days of my wound care career, I promoted practices that didn’t meet those criteria because I trusted the clinicians teaching me were doing the right thing. 

However, I began to question things as my knowledge grew. After doing the research, I was shocked to learn some tried-and-true practices weren’t so tried and true after all.

In this blog post, we delve into one of those methods — the use of Dakin’s solution and acetic acid in wound care.

Let’s review Dakin’s solution

Dakin’s solution was first developed in World War I through a collaborative effort between English chemist Henry Dakin and French surgeon Alexis Carrel. 

They developed the sodium hypochlorite solution and an apparatus that continuously instilled the solution because of its short-acting antimicrobial properties.

Dakin’s solution is available in four strengths:

  • 0.5% (full strength)
  • 0.25% (half strength)
  • 0.125% (quarter strength)
  • 1/40 (0.0125%)

Only 0.0125% is non-cytotoxic to tissue and cells. 

Full strength is only recommended by the U.S. Centers for Disease Control and Prevention (CDC) for disinfecting surfaces because this is the lowest strength that will not damage skin, according to an article in the journal Advances in Skin and Wound Care.

The current antimicrobial testing on half- and quarter-strength solution has only been done in-vitro, which does not correlate with clinical effectiveness in wounds.

There are no clinical studies that quantitatively measure bacterial levels in wounds after treatment with Dakin’s, only that the wounds showed improved healing. 

Dakin’s solution safety

To assume that means “it must have reduced the bacteria” is poor critical analysis of the data. One should never assume.

As a matter of fact, the U.S. Food and Drug Administration (FDA) has not found half-strength Dakin’s to be safe and effective. The FDA clearance for commercial quarter-strength Dakin’s solution states the sodium hypochlorite acts as a preservative within the solution, and there is nothing about directly affecting microorganisms within the wound. 

With all this obvious evidence — or lack of — regarding the use of Dakin’s solution, there are other questions you also should consider. 

  1. What strength did Dakin and Carrel use in their practice? I wasn’t able to find a resource to confirm this.
  2. Why are we only applying one to two times a day when they did continuous instillation?
  3. What is the effect in chronic wounds since Dakin and Carrel only used it on acute wounds?

Though Dakin’s is probably the best-known sodium hypochlorite product, it is not the only one. Hypochlorites exist in other forms, including non-cytotoxic products such as Anasept cleansers.

Let’s explore acetic acid (vinegar solution)

Acetic acid is a mixture of vinegar and water. Standard vinegar is about a 4% acetic acid concentration. 

Vinegar’s use can be dated back to third century B.C. in the area of alchemy. It wasn’t until the early 20th century that we find acetic acid being introduced into wound care.

Many different concentrations have been used — from 5% to as low as 0.25%. Evidence has established that a minimum of 0.5% is necessary for effective antimicrobial effects, but most studies have used a 1% concentration, with some up to 3%. 

Acetic acid has a two-fold effect in that it kills microorganisms and decreases the pH of the wound. A healing wound generally has a pH closer to neutral.

Using acetic acid would lower the pH to inhibit bacterial growth (1% acetic acid has a pH of 2.4) versus higher wound pH that is friendlier to bacterial growth, according to research by the Indian Journal of Plastic Surgery. Its cytotoxic effects are conflicted in that acetic acid is cytotoxic in vitro, but in vivo studies were not conclusive.

Questions on acetic acid studies

Studies have shown it to be effective against pseudomonas in burns and skin infections

However, upon closer analysis of methods used and conclusions, a couple of significant issues with the acetic acid studies became quite evident. 

  1. First, they either used a swab culture, which cannot quantitatively measure bacteria levels in a wound, rather only what is present. Or they didn’t specifically mention how they arrived at the “reduction or elimination of bacteria,” the Indian journal noted. 
  2. Secondly, some studies concluded they “eliminated” the bacteria in the wound. The challenge with this notion is it suggests “sterilization” of a wound is possible. We know from real-world science that sterilization of a wound is impossible, and reduction of the bacteria is our best hope. 

Although use of these agents has been promoted for decades as effective antimicrobials, the evidence does not bear that out.

The common response of “I have used it on many wounds and it works” is anecdotal, which is not real evidence. Our patients deserve the best 21st century wound care we can provide.

Take our online Skin and Wound Management course to learn more.

Bill Richlen, PT, WCC, DWC
Bill Richlen, PT, WCC, DWC

Bill Richlen, PT, WCC, DWC, is a licensed physical therapist and has experience in advanced wound care consultations in long-term care, outpatient, skilled rehabilitation and home health. He has served as a clinical instructor for physical therapy students, been the director of several large rehabilitation departments, and has been providing multi-disciplinary wound care education to nurses and therapists for over 17 years. His expertise in diverse settings enhance his role as a clinical instructor. Bill’s dynamic and captivating teaching style keep’s attendee’s attention throughout the course.

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