Do I want reagent-grade chemicals on my face?

November 6, 2005 6:50 PM

FormularyFilter? Compounding my own salicylic acid facial peels: do I need to use pharmaceutical grade ingredients?

I'm planning to make a salicylic acid facial peel (for my own use, not to sell) using ingredients I'll buy online--namely, powdered salicylic acid.

Looking at chemical supply websites (Sigma-Aldrich, Gallade, Cole-Parmer) I assumed that I should buy USP or pharmaceutical grade, since those would be the most pure and (I figure) the safest. I don't need a whole kg or even the 125 grams that companies offer, and the stuff (especially pharmaceutical grade) isn't cheap, so I checked out ebay. I emailed someone selling small amounts of salicylic acid to ask what grade it was, and she replied that it was reagent grade, "for topical use and I do not recommend ingesting it." (Why I'd want to ingest salicylic acid is beyond me, but anyway...)

Are reagent grade (or other non-pharmaceutical grade--CP grade, NF grade) chemicals safe to put on my skin, in the appropriately dilute concentrations (20-30% by weight in the case of salicylic acid peels)? I'd assumed that using pharmaceutical grade chemicals would be necessary for topical pharmaceutical use in addition to enteric use, but the ebay lady's response suggests otherwise. When I think about it, it's probably an issue of purity, and potential contaminants may be dangerous to ingest but fine topically.

Alternatively, where can I buy very small amounts of pharmaceutical-grade salicylic acid? A few grams of it would probably be inexpensive enough that I'd just spring for the higher grade whether or not it's necessary. I also welcome suggestions of where to buy larger amounts--i.e. if there are chemical companies that are particularly pleasant to buy from, name 'em!

I understand the risks involved in doing a facial peel myself, and I believe I have enough experience with chemicals to calculate and mix things correctly, so please don't lecture me about those aspects of safety.

posted by needs more cowbell to science & nature (12 comments total)

Salicylic acid is naturally occuring in willow bark. Obtaining large quantities by extraction is probably cost-prohibitive, but you may be able to get enough for personal use that way.
posted by ijoshua at 7:34 PM on November 6, 2005

Aspirin is a derivative of salicylic acid. I'm guessing that is why there is a comment about not ingesting it, (people might think it's aspirin?).
posted by 6:1 at 7:35 PM on November 6, 2005

Seconding the aspirin. It's an easy way to get a Beta Hydroxy Acid peel for cheap. Get the uncoated, unbuffered kind, crush up about 10 or so, mix with a small amount of water, smear it all over your face and let dry.
posted by 4easypayments at 7:40 PM on November 6, 2005

Salicylic acid is produced industrially by carbonylation of phenol (deprotonate phenol with sodium hydroxide, add CO2, then acidify to form the acid). Reagent greade salicylic acid is, therefore, contaminated with phenol, a known mutagen. Pharmaceutical-grade salicylic acid is futher purified to remove phenol (and probably other contaminants).

I don't want to lecture you on what you're set on doing, but you really should avoid buying this stuff off of eBay, and don't buy reagent grade chemicals to save a buck.
posted by istewart at 7:48 PM on November 6, 2005

ijoshua, I'd guess that any salicylic acid I extract from willow bark on my own would probably be less pure than reagent-grade stuff I could buy. I suppose I would at least know what went into my product, which would be useful if I knew that everything used was not harmful when absorbed through the skin, but I'm not sure how likely that is. Also, while I'm confident in my skill at calculating and mixing, my knowledge of organic chemistry is really rusty (and I don't have a lab at my disposal). Unless it's incredibly easy...have you done it before?
posted by needs more cowbell at 7:56 PM on November 6, 2005

Thanks istewart, that's exactly the sort of thing I wanted to know. I hadn't thought about contaminants being mutagens, and I will definitely avoid reagent-grade chemicals.
posted by needs more cowbell at 8:03 PM on November 6, 2005

It's possible you're being quoted high prices because you're not affiliated with an institution that makes high volume purchases. I just checked our lab's supplier (VWR), and our institutional price for USP-grade salicylic acid is $20 (Canadian) for 125 grams. Not so bad, compared to a lot of other things we buy. Do you have any acquaintances in the medical/research profession who might be willing to order it for you?
posted by greatgefilte at 8:46 PM on November 6, 2005

Slightly off the topic, but it's worth emphasising that "more pure" is not the same as "less dangerous". It depends what the impurities are. When I did my first stint in a lab as an undergraduate, I was advised to drink the 95% pure ethanol rather than the 99% - in the former, the other 5% was water, but in the latter the remaining <1% was benzene and pyridine and all sorts of nastiness. I didn't drink either, but the lesson stuck.

Reagent-grade salicylic acid will be purer than something that you make from willow-bark, but if that other 1% is phenol you don't want to be putting it on your face.
posted by nowonmai at 9:26 PM on November 6, 2005

I realize that, nowonmai, and it's a good point. I'm not sure what I'd need to use to extract salicylic acid from willow bark, but I think it's likely that whatever I used to do it myself would leave (harmful) impurities (phenol or others) as well.

On second thought, I suppose I might be able to extract some amount of salicylic acid from willow bark just by boiling it or soaking it in alcohol--I'm looking for a 20% concentration, and it doesn't matter much what the other 80% is as long as it's not harmful. But I'd have no way of knowing what the concentration was, or even if I'd extracted any salicylic acid at all.
posted by needs more cowbell at 9:48 PM on November 6, 2005

$20 Canadian is pretty reasonable, greatgefilte--I'd been seeing prices upwards of $45 US. I'll see if anyone I know has ordering privileges at institutional prices...if not, would you be interested in making a deal, by any chance?

[I suppose this is where I kick myself for leaving my (very brief) job in the chemistry department stockroom on such a sour note. ]
posted by needs more cowbell at 10:01 PM on November 6, 2005

But I'd have no way of knowing what the concentration was, or even if I'd extracted any salicylic acid at all.

If you're really interested, take an introductory organic lab class at your local community college. They'll teach you how to safely extract and purify organic compounds.

You'll likely refer to Beilstein's or the CRC Handbook of Chemistry and Physics, which are references that contain tables of attributes for thousands upon thousands of chemical compounds, including salicyclic acid. This will tell you about things like what this acid is soluble in, which will help you figure out a safe(r) way to extract and use your product.
posted by Rothko at 2:12 AM on November 7, 2005

nmc -- I see that in the US, you can actually get 100g for $15, at non-institutional prices (see this page.) The only question is whether they'll ship to an ordinary citizen or not.

I'd have to look into whether or not I can ship to you -- are you in the US or Canada? Email me...
posted by greatgefilte at 10:42 AM on November 7, 2005