Where do medical myths come from? More than a half century ago, a myth circulated that polio might be caused by summer air. Another myth was that anything that entered bodily tissues would ultimately be rejected (even though there had been limited success with hip implants). As a result, people often stayed indoors on summer evenings and implantable devices were considered a foolish notion until about 60 years ago. Today, it is known that polio spreads via fecal-oral transmission of the polio virus, and new materials have made implantable devices commonplace.
More recently, myths about cotton neutralizing chlorhexidine gluconate (CHG), CHG irritation, and CHG “washing off in the shower” are circulating because of a lack of understanding of how CHG works and from pervasive misinformation. The purpose of this article is to “bust” these myths.
The myth that cotton neutralizes CHG probably started because of confusion about how CHG binds to the stratum corneum of skin. One might assume that CHG would also bind to cotton or other materials often used to apply CHG antiseptics.
The neutralization myth was given some credibility by Dr. Graham Denton, a well-known CHG researcher who reported that CHG in solutions can bind to cotton. In discussions with Denton, he clarified that the amount of CHG that would likely be bound to a cotton washcloth during normal use would be minuscule, perhaps even undetectable. His research on CHG binding to cotton was performed on low-concentration CHG formulations packaged with towels of different materials for long periods of time.
To address this myth, a limited study of the interaction of cotton washcloths with 4 percent CHG was performed. The CHG level was unaffected when applied to a wet or dry cotton washcloth for five minutes, measured and repeated.
Water in wet washcloths diluted the CHG and changed its concentration. However, the original amount of CHG was present in the water squeezed from them.
The study, which measured CHG levels in Hibiclens®, suggests that the CHG levels are unaffected when applied to either a wet or a dry cotton wash cloth. So, the myth about cotton washcloths neutralizing CHG is not true. Myth busted!
Why is this important? Well, there are many chemical and physical interactions that can affect antiseptic efficacy:
storage temperatures (hot and cold)
spectrum of kill
chemicals (lotions, soaps, other antiseptics, wound care ointments, etc.)
Knowing that cotton washcloths do not neutralize CHG is one less thing to worry about.
Another popular myth is that CHG is very irritating, and that 2 percent CHG is milder than 4 percent CHG. A recent irritation study showed the opposite – 2 percent CHG antiseptics in the study were potentially more irritating than 4 percent CHG antiseptics of the same brand and potentially much more irritating than the most popular 4 percent CHG antiseptic. Myth busted!
How can a 2 percent CHG antiseptic be more irritating than a 4 percent CHG? The answer is that CHG is usually not the primary source of skin irritation. CHG is only 2 percent to 4 percent of most formulations; 96 percent to 98 percent of the formulation consists of “other ingredients.” Based upon dermatological testing, it appears that it is usually ‘other ingredients’ that cause irritation, not CHG.
So, using a 2 percent CHG means using a lower concentration of active ingredient, which is not quite as effective as 4 percent, and the 2 percent CHG product’s irritation potential is greater in some instances. It just does not make clinical sense to use a 2 percent CHG product, knowing that 4 percent CHG products can provide greater amounts of active ingredient, usually with less irritation. (See Figure 1)
Figure 1: Hibiclens® Irritation Studies Summary
The latest myth is that CHG washes off with water and provides no residual killing power. A simple handwashing demonstration ‘busts’ that myth. When the most popular 4 percent CHG antiseptic was applied as a surgical hand scrub (according to the tentative final monograph), the scrubbed hands killed Staphylococcus aureus when placed onto a S. aureus-inoculated agar plate six hours after the final wash. Whether handwashing, surgical pre-operative prepping, general skin cleansing, skin wound treating or surgical hand scrubbing, CHG works the same. It binds to the skin stratum corneum and maintains residual killing power for up to six hours. (See Figure 2.)
Figure 2 at lower right.
So, all of the CHG does not go down the drain when the skin is washed. In fact, much of it binds to the skin and keeps on killing – long after alcohols, iodophors, PCMX and other antiseptics have stopped killing and/or have been washed off the skin. CHG works very differently from other antiseptics, yet many people probably assume that it works the same and erroneously accept the myth that it all washes off and goes down the drain.
Hopefully this information will dispel several of the myths about CHG products. Just remember that medical myths abound, disguised as truth — “a wolf in sheep’s clothing,” so to speak. So watch out for myths and eliminate them with education and an inquiring mind. ICT
Milt Hinsch is the technical services director of Mölnlycke Health Care, and can be contacted at (678) 250-7920 or [email protected]. Mölnlycke Health Care US, LLC sells Hibiclens® Antiseptic/Antimicrobial Skin Cleanser, Biogel® Surgeons Gloves and Barrier® Wearing Apparel.