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From Wikipedia:

Household use of antibacterials in soaps and other products, although not clearly contributing to resistance, is also discouraged (as not being effective at infection control).

Following the links led me to this paper: Larson EL, Lin SX, Gomez-Pichardo C, Della-Latta P., Effect of antibacterial home cleaning and handwashing products on infectious disease symptoms: a randomized, double-blind trial. Ann Intern Med. 2004 Mar 2;140(5):321-9.

They conclude:

The tested antibacterial products did not reduce the risk for symptoms of viral infectious diseases in households that included essentially healthy persons. This does not preclude the potential contribution of these products to reducing symptoms of bacterial diseases in the home.

Upon reading this, my thoughts were: Why would one test whether antibacterial products have an effect on viral infections diseases? Since the authors used a control group (those whose soaps didn't have an antibacterial agent), they are only testing for the effect of the antibiotic.

This leads me to the main question:

Question: Which common diseases would likely be more affected by antibacterial hand soaps (and other antibacterial products) than their non-antibacterial counterpart?

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psychosomatic illnesses? Soap is a pretty potent anti viral and anti bacterial all by itself. Hospitals and doctors use Purelle or other alcohol based gels to keep their hands clean. The weak antibiotics in antibiotic soaps like triclosan are probably encouraging the formation of antibiotic resistance. –  shigeta Feb 22 '12 at 9:15
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2 Answers

This may be related to this question on Skeptics SE: Does regular handwashing with antibacterial soap prevent disease? Since it is closely related, I will copy my answer from there to here:

See this related answer.

To answer your specific questions:

Has something changed?

Well, we have access to these products now, whereas we didn't before.

Does this sanitizing really make people healthier?

That is a subject of debate. While it can prevent rapid spread of some things, keep in mind that anti-bacterial soaps should only have specific uses.

The CDC has concerns about the prevalent use of these products.

Scientists are concerned that the antibacterial agents will select bacteria resistant to them and cross-resistant to antibiotics. Moreover, if they alter a person's microflora, they may negatively affect the normal maturation of the T helper cell response of the immune system to commensal flora antigens; this change could lead to a greater chance of allergies in children. As with antibiotics, prudent use of these products is urged. Their designated purpose is to protect vulnerable patients.

Also, there is some concern as outlined by the hygiene hypothesis (WP). However, that is mostly associated with childhood immunities and allergies as opposed to the effects on adults.

“The natural immune system does not have as much to do as it did 50 years ago because we’ve increased our efforts to protect our children from dirt and germs,” says McMorris.

“Allergies are on the rise because our society has changed the way we live. As a result, people with allergies are having children with others who have allergies, which in turn creates a natural increase in the prevalence of allergies in our society.

The bottom line on this hypothesis is that more research is required.

He (Richard G. Barbers, M.D., USC professor of medicine at the Keck School) also gives credence to the hygiene hypothesis in that "we may be over-protecting kids, and their immune systems, consequently, do not become well-developed."

Barbers notes that only time and a lot more research will tell whether the hygiene hypothesis is valid, and whether, once again, parents should let their kids play in the dirt.

It is generally understood that interaction with beneficial germs is good for you. However, normal cleaning will not destroy these germs since they reside within you (unless his germaphobia induces him to take antibiotics). The human immune response doesn't particularly work that way.

The investigators show that "good" bacteria in the gut keep the immune system primed to more effectively fight infection from invading pathogenic bacteria. Altering the intricate dynamic between resident and foreign bacteria - via antibiotics, for example -- compromises an animal's immune response, specifically, the function of white blood cells called neutrophils.

Using too many anti-bacterial soaps has raised quite a few concerns even still.

Soaps and lotions that include antibacterial agents have no benefit over ordinary soap and water, but more research is needed to allay or substantiate concern that these substances may be leading to increased rates of antibiotic resistance. This is the conclusion of the Food and Drug Administration's Nonprescription Drugs Advisory Committee, which met last month to consider the use of these products outside of the health care setting.

"In the absence of proven benefit, there's no real reason to encourage the use of these products," said Alastair J.J. Wood, MD, committee chair and associate dean at Tennessee's Vanderbilt Medical School.

That is not to say that their use should be discontinued entirely. Two MDs weigh in and conclude:

Opt for regular soap and water, unless you’re at a hospital or doctor’s office, where it’s best to use antibacterial soap. But if you’re out and about and antibacterial soap is the only kind around, it’s fine to wash with it—and it’s worth keeping in the kitchen to use after handling raw meat.

Hope that helps.

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I thought I would attempt to answer my own question. The only other answer currently (by Larian LeQuella), while a helpful comment, I feel it doesn't answer my original question.

To begin, we need to put the results into context.

Fact: Hand-washing using tap water alone will reduce the amount of bacteria and viruses on hands (they might not be actually killed, but no longer on your hands).

Some examples:

  • Ansari et al. (1989) performed an experiment where a fecal solution was placed on participants' hands and subsequently washed off using one of a range of soaps. They found a reduction in around 83% of the human rotavirus and 90% of the E. coli.

  • Shojaeia et al. (2006) randomly selected 150 food handlers in Iran, and instructed them to wash and scrub their hands with sterile water. Before the intervention, around 73% were contaminated with bacteria (primarily with Staphylococcus aureus or E. coli), and afterwards 32%.

Fact: More bacteria and viruses are removed from hands by hand washing by using some type of soap (not necessarily antibacterial).

Some examples:

  • Ansari et al. (1989) (op. cit.) found that certain agents (e.g. 70% isopropanol) can increase the reduction in E. coli and human rotavirus to around 98%. However, this was not true of all possible hand-washing agents.

  • Mbithi et al. (1993) also conducted a experiment consisting of placing a fecal solution on participants' hands that was subsequently washed off using one of a range of soaps. In this case, the hepatitis A virus (HAV) and poliovirus type 1 (PV) was considered. They found that tap water gave a reduction of HAV of around 80% and PV of around 85%. The reduction increased to around 88-92% for HAV and 90-98% for PV for most soaps tested.

[There will be zillions of additional examples to the above.]

A large survey was conducted by Aiello et al. (2007) which considered the efficacy of triclosan (one of the common active ingredients used in antibacterial hand soap) found that, overall, previous research has indicated no significant additional benefit vs. ordinary hand soap. They write:

Soaps containing triclosan within the range of concentrations commonly used in the community setting (0.1%–0.45% wt/vol) were no more effective than plain soap at preventing infectious illness symptoms and reducing bacterial levels on the hands.

This is probably not the last word on the matter, e.g. Fischler et al. (2007) claimed a significant difference in the transmission and acquisition of E. coli and Shigella flexneri after using an antibacterial soap. It is also plausible that antibacterial agents other than triclosan (where the focus has been) provide a health benefit (for example, methylchloroisothiazolinone/methylisothiazolinone). In fact, the Aiello et al. (op. cit.) paper itself indicates a non-negligible effect from >1% triclosan. Kimberly-Clark give a 99.9% or more bacterial killing efficacy for a range of bacteria in a 2003 in vitro experiment of their product; obtainable via Googling "kimberly-clark killing efficacy".

(Side note: There is also a suspicion that the use of triclosan will give rise to triclosan resistance or cross-resistance to antibiotics (e.g. by Levy (2001), Aielloa and Larson (2003), Yazdankhah et al. (2006)). Although, Cole et al. (2003) and Weber and Rutala (2006) claim otherwise in the case of antibiotic resistance.)

This leads to the original question: Which common diseases would likely be more affected by antibacterial hand soaps (and other antibacterial products) than their non-antibacterial counterpart? I.e. if we wanted to test the claim that a certain antibacterial hand soap has some positive effect (vs. a non-antibacterial version), what would be some common diseases that we could test for, and expect to find a non-negligible result?

I offer the following candidate for a bacterial disease whose effect should be noticeably reduced by the use of antibacterial hand soaps:

  • Staphylococcus aureus is a bacterial species that causes a range of noticeable illnesses and can be transferred by skin-to-skin contact and contact with contaminated objects. We can thus reasonably expect it to be affected by an effective antibacterial hand soap. In fact, washing hands is recommended for reducing the prevalence of S. aureus, along with zillions of other diseases (by e.g. Better health channel). This is one of the bacteria that Kimberly-Clark give a 99.99% kill efficacy of their product in vitro.

Although, not directly related to hand-washing, Brady et al. (1990) used a 1% triclosan preparation and Zafar et al. (1995) used 0.3% triclosan to control methicillin-resistant Staphylococcus aureus.

The single additional measure of changing handwashing and bathing soap to a preparation containing 0.3% triclosan (Bacti-Stat) was associated with the immediate termination of the acute phase of the MRSA outbreak. -- Zafar et al.

Similarly, a 1.5% triclocarban bath has been used to treat atopic detmatitis Breneman et al. (2000):

The antimicrobial soap regimen caused significantly greater improvement in the severity and extent of skin lesions than the placebo soap regimen, which correlated with reductions both in S aureus in patients with positive cultures at baseline and in total aerobic organisms.

The above results suggest that antibacterial soaps could have a beneficial effect against S. aureus (more than a non-antibacterial counterpart). However, it is unclear as to how much of this effect implies a comparable effect for hand washing alone (and in an ordinary household setting). Moreover, there are many different antibacterial hand soaps and other products, whose active ingredients might be at different dosage, all of which would further affect the outcomes.

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