Lets take the product that lew just posted on his blog.
http://www.amazon.com/dp/B001ET7BT4/ref=as_li_ss_til?tag=lewrockwell&camp=213381&creative=390973&linkCode=as4&creativeASIN=B001ET7BT4&adid=0AWGC5D9P0QS35Z5CXDM
Collyrium
Ingredients Active: Boric Acid, Sodium Borate, Sodium Chloride and Purified Water. Inactive: Preservative Added: Benzalkonium Chloride.
Why in the world do you need to add a preservative to this? What are you preserving?
Purified Water? no, that should never go bad.
Boric Acid? does that go bad? I can't imagine that it does.
Sodium Borate? same thing as above.
Sodium Chloride? Salt is a preservative for cryin out loud
Someone help me out here. Why do they put preservatives in these eye drops?
"Purified Water" ceases to be purified as soon as you open the package so I would hypothesize that it is perhaps used to preserve the product after opening. Benzalkonium Chloride is also used in anti-septic applications which suggests to me that it would perhaps help to keep the drops sanitary if some contaminant found it's way in.
I don't have any proof, though I did find that in an alternative product (also eye-drops) this statement was present: "Contain a mild, well-tolerated preservative, known as silver sulphate in the 10ml bottle. Trial sizes and single-use droppers do not contain a preservative. [emphasis mine]"
You are spot on.
Benzalkonium Chloride is used both to combat microbial contamination of the containers and to break cell-cell junctions in the corneal epithelium, allowing drops to enter the anterior chamber where they are needed the most.
Its value as a preservative comes from being able to disturb the cellular walls in bacteria. To cut a long story short it disrupts the lipids making up the "cell walls" in bacteria, making them "fall apart". It starts to be effective at around 0,05% (in volume) but it's mostly effective at around 0,1%. There are some known side effects but, unless you abuse of eye drops on a daily base or have glaucoma, you will have no problem.
About Silver Sulfate... among its Risk Phrases (did you pay attention in chemistry class? I hope you did) is R36, irritating to the eyes.
Thanks.
The comment for silver sulfate was only to point out that in that instance they do not include it in single-use versions of the same product (i.e. one that would only ever be opened once).
"and to break cell-cell junctions in the corneal epithelium, allowing drops to enter the anterior chamber where they are needed the most."
So, you're saying Benzalkonium Chloride solutions work better at cleansing the eye than water solutions without Benzalkonium Chloride?
Technically speaking no, it just allows the active components (most common are boron salts and boric acid) to get where they are needed the most easily. I am a chemist with a strong interest in biochemistry, not a doctor, but I'll try to explain to the best of my capabilities: our eyes are built in "layers". The outermost of these layers is the corneal epithelium, which acts a first barrier of sorts to protect the cornea from bacteria and resist the free flow of fluids from tears (even when we are not crying are eyes are constantly "kept moist" by secretion from the lacrimary glands). Benzalkonium chloride allows the drops to pass through this first barrier by "weakening" it for a brief moment, get to the stroma (and in primates such as ourselves through Bowman's membrane), Descemet's membrane and finally into the anterior chamber.
"Technically speaking no, it just allows the active components (most common are boron salts and boric acid) to get where they are needed the most easily. I am a chemist with a strong interest in biochemistry, not a doctor, but I'll try to explain to the best of my capabilities: our eyes are built in "layers". The outermost of these layers is the corneal epithelium, which acts a first barrier of sorts to protect the cornea from bacteria and resist the free flow of fluids from tears (even when we are not crying are eyes are constantly "kept moist" by secretion from the lacrimary glands). Benzalkonium chloride allows the drops to pass through this first barrier by "weakening" it for a brief moment, get to the stroma (and in primates such as ourselves through Bowman's membrane), Descemet's membrane and finally into the anterior chamber."
thanks for the info..
but why would we want boric acid and this other stuff to pass through to the other layer of our eyes?
Boric acid is an antiseptic and an antibacteric and is also one of the very acids that has no ill effects on the eyes.
"Boric acid is an antiseptic and an antibacteric and is also one of the very acids that has no ill effects on the eyes."
So, if I just want to wet my eyes and not use antiseptic on them, just use purified water? Sort of like wanting to wash my hands with actual soap, not antibacterial detergent?
They used to add mercury based preservative thimerosal!!
I think you'll find that water without some salt is not nearly as comfortable.
so maybe a little purified water and salt.
without all the antiseptic and chemicals used to breakdown the outer layer of the eye.
"thimersal"
sounds like they have a really bad history of using ridiculous preservatives.
limitgov: so maybe a little purified water and salt. without all the antiseptic and chemicals used to breakdown the outer layer of the eye.
Yeah, cooking up your own batch of eye wash is probably a bad idea >_>
Too much or too little salt and you'll sting, as you either inject too many ions or too few causing ion travel. The salt is there to match the salinity of your natural tears.
Anenome wrote the following post at Wed, Sep 21 2011 11:26 PM: Yeah, cooking up your own batch of eye wash is probably a bad idea >_>
- That is not the issue. The question is, why can't the companies producing eye wash/eye drops/contact lense solution without known toxins.
"Yeah, cooking up your own batch of eye wash is probably a bad idea >_>"
I never said remove the salt.
I never said you were going to remove the salt :P
But, do you have the proper tools to measure ion concentrations in human tears and reproduce that? On a stove?
I picture you with a pot of water and a salt shaker :P
If you're really that concerned, buy some sterile saline. AFAIK it won't have the other ingrediants you're worried about. Except that, upon opening it, it won't remain good for very long, as there's many living organisms out there which tolerate salt water just fine.
Phil Ridley: - That is not the issue. The question is, why can't the companies producing eye wash/eye drops/contact lense solution without known toxins.
Define 'toxin.'
The answer is, they could. Just like they could produce food without preservatives.
But the value to users wouldn't be as high.
I have a bottle of Visine that expired five years ago (I use it rather rarely). Still works fine :P Try that with your self-concocted mix / non-preservative mix.
Frankly, better question the need for eye drops in the first place. If we agree that saline solution is bacterio-static, and that tears are saline, then maybe the need for eye drops is a salt deficiency? The USDA's dietary guidelines almost eliminate salt, and it is being replaced with toxic MSG in many processed foods.
Now, I differentiate here between unrefined seasalt/rocksalt, which has all the minerals the body requires, in the right proportions, in easy to assimilate electrolyte form, vs table salt which is pure sodium chloride. The biggest joke about reducing salt consumption is that the body reacts by exreting less in tears, sweat and other places that require salt. Of course, extra table salt will enhance mineral imbalalance, but that is not the case for unrefined sea/rocksalt. I recommend celtic seasalt and himalayan rocksalt.
The most recent journal of the Weston A Price Foundation covered this issue:
- http://www.westonaprice.org/journal/journal-summer-2011-salt-and-sulfur
"But the value to users wouldn't be as high."
That is not true. Foods without preservatives are MORE EXPENSIVE.
limitgov: "But the value to users wouldn't be as high." That is not true. Foods without preservatives are MORE EXPENSIVE.
You're just revealing that you don't understand the economic use of the term 'value.'
By 'value' I don't mean mere product gotten for the money, I mean value in the sense of what it is about a product that makes one person choose to buy it over another product, of which product gotten for the money is only one criteria.
Your average consumer will consider all sorts of variables before picking X product over Y product.
Sure the product is more expensive, but it may be that people value a more expensive, but long lasting product, over cheaper products that won't last as long.