Antibacterial additive commonly used in consumer products such as deodorant soaps and "antibacterial" cleaners — the ingredients list on any bar of antibacterial soap will probably include triclosan. It works by inhibiting an enzyme, called FabI, needed for fatty acid synthesis and bacterial survival. Triclosan has been touted as a non-specific agent that attacks bacterial membranes and kills randomly, therefore not encouraging resistant strains.

In July of 2000 a research team at St. Jude Children's Research Hospital discovered that Streptococcus pneumonia has an alternative enzyme called FabK, which is unaffected by triclosan. Also, escherichia coli has demonstrated mutations in FabI which also can cause triclosan resistance. With widespread use of triclosan, resistant strains of this nature can be expected to become more common.

Since antibacterial soap is considered no more effective than regular hand soap in normal cleansing, there is some call for regulating the use of triclosan.

Purell and Ivory soap are considered good hand sanitizers, and do not contain triclosan.

Sources for this writeup include: ,

Triclosan is one of the more common antibacterial agents used in soaps, mouthwashes, toothpastes, deodorants, cosmetics, and etc., etc., etc. It is also sometimes embedded in clothing and plastics, in which case it is usually is marketed as Microban, and in acrylic fibers, in which case it is marketed as Biofresh.

Although triclosan has been approved for use by both the U.S. Food and Drug Administration and by the European Union, there are some health and environmental concerns. Various people have tried for various reasons to have it banned. Banning it is probably a bit extreme, but the amount of triclosan we currently use is also extreme.

  1. Bacterial resistance: There is some evidence that some types of bacteria (for example, E. coli) can form resistances to triclosan {3}. Most studies have shown that the likelihood of bacterial mutations is very low -- low enough that they recommend using triclosan, at least in situations in which you are preparing food for others, working in medical settings, or cleaning cuts and minor injuries {2}. One study found no significant increase in antimicrobial drug resistance after one year of triclosan use in normal household conditions {5}. Of course, triclosan has been used for billions of hours of 'normal household conditions', along with, one assumes, some abnormal household conditions. So far it hasn’t been suspected of having created any dangerous mutants.

    Update: Clostridium difficile, Serratia marcescens and Pseudomonas putida have come to light as bacteria that are not killed by exposure to triclosan. No doubt there will be many others discovered/evolved in the next few years.

  2. Chloroform gas: Triclosan combines with chlorine to form, among other things, chloroform gas, which is a suspected human carcinogen. Chlorine, of course, is present in small amounts in most tap water. This has caused some cancer scares, but the amount of chloroform gas created is very small, so that you would have to be using a lot of triclosan to expect any negative effects... but we do use a lot. I haven't found any statistics on how much triclosan is used daily by the average person vs. how much is needed to be a serious cancer risk from chloroform gas. There are however, studies that use the creation of chloroform gas in addition with the creation of other toxins to show that triclosan is a health risk {7}{a}.

    It is also possible that swimming in a chlorinated swimming pool might present the same risk if you have previously used skin care products containing triclosan {8}. This is not something that you hear much about, and is not likely to be a significant risk.

  3. Dioxins: Dioxins are bad. They can weaken the immune system, cause birth defects and decreased fertility, and cause cancer -- among other bad things. Dioxins are bioaccumulative (while they do break down, they do it very slowly). Dioxins can be found in triclosan as impurities formed during the manufacturing process, and triclosan can break down into various types of dioxins when added to water and then exposed to UV radiation (the chlorine molecules in tap water can make it even worse).

    To state that again, in simpler language: Triclosan + Water + Sunlight = BAD. Dioxins harm fish and accumulate in their tissues {9}. When we eat the fish, the dioxins can pass on to us. Algae are also affected, and if you live near a river, you know that what affects algae can affect us all.

Triclosan is found in three out of five breast milk samples (in Sweden) {10}. Triclosan overuse is linked to an increase of allergies {6} (as happens with the overuse of other antibacterial agents). Triclosan has been shown not to help fight the spread of colds and the flu. Triclosan looks like cocaine (a white powder; close enough). Triclosan is fun to pick on.

So, is triclosan the next DDT? Well, probably not. But we do use a lot more of it than we need to, and probably a lot more than is good for us. You don't really need an antibacterial soap under normal circumstances. If you are doing something that could spread germs to a number of other people, then it's not a bad idea to use triclosan or some other antibacterial soap, but for everyday purposes, 'normal' soap plus some common sense and basic hygiene is plenty good enough, and safer for us all.

Products that use triclosan are required to say so somewhere on their label. Chances are that if it says antibacterial on the label in big letters, it will say triclosan somewhere on the back. You may not feel the need to avoid the product, but you should at least think about why a given product needs to kill bacteria.

Technical details.

Systematic name; 5-chloro-2-(2,4-dichlorophenoxy)-phenol
AKA; 2,4,4'-trichloro-2'-hydroxydiphenyl ether < br /> Molecular formula; C12H7Cl3O2
SMILES; C1=CC(=C(C=C1Cl)O)OC2=C(C=C(C=C2)Cl)Cl
Molar mass; 289.5 g/mol
CAS number; 3380-34-5

{9} (PDF format)
{a} I haven't read the actual article, but since I have the reference I thought I should post it, for those of you with access to a decent library. Kristopher McNeill and William Arnold, Envir.Toxicol.Chem. 2005, 24, 517-525

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