Alum block after shaving: Alzheimer's risk?
November 26, 2012 9:55 PM   Subscribe

So I hear that aluminum is pretty bad for your body (and maybe is linked to Alzheimer's?). I also hear that alum (which is used to close nicks after shaving) is the name of an aluminum compound. The majority of info about alum crystals for personal hygiene tends to be on "natural living" web sites and the like, so my main question is: is there any actual scientific study either way as to the safety of such a thing being rubbed on your face on a regular basis?
posted by DoctorFedora to Science & Nature (6 answers total) 4 users marked this as a favorite
I do know that shaving alum is the potassium alum (potassium aluminum sulfate) in most cases, rather than ammonium alum. It's also found in powdered form as a pickling spice, because its astringent qualities means it can make pickles shrink. And I use it while shaving (followed by witchhazel)-- the alum gives me a basic map of my face in terms of where I scraped my skin with the razor, by highlighting the invisible scrapes with stinging pain.

As far as I'm aware, the aluminum-Alzheimer's link was that Alzheimer's patients had more aluminum in their brains than non-patients. This link caused a nosedive in the sale of aluminum cookware back in the 1990s, and a few people changed deodorants (though nearly all of them use some form of aluminum salt as a drying agent for your pits), and it's mostly forgotten about these days, I feel, so either it was discredited, or the correlation did not prove to be causation.

The layer being applied to your face is so very thin it's basically invisible, and when it's doing its job, it's causing your skin to retract and thus your pores to slam shut, so it's hard to see how it would be a threat compared to, say, waving a razor around your neck every morning while groggy.

But I have no science on the topic, so I am interested as well.
posted by Sunburnt at 10:23 PM on November 26, 2012

Best answer: As far as I know the aluminum-Alzheimer's link has been written off as a flawed experiment, after multiple failures to replicate it. I was about to hunt down some links, but you can probably find everything I would here: Previously, previously, previously on AskMe.
posted by hattifattener at 10:34 PM on November 26, 2012 [14 favorites]

Response by poster: Awesome! I am ALL ABOUT finding out that scary class-action-type health scares are either nuanced or simply the results of mistaken interpretations of test results.
posted by DoctorFedora at 11:30 PM on November 26, 2012

Even assuming aluminium is harmful, you'd need to confirm that using alum (an aluminium salt) on your skin leads to increased bio-availability, i.e. that you end up with more aluminium ions in your body.

A quick google shows that alum treated water does show an uptick in men of alum in urine, but NOT aluminium in blood plasma - i.e. it's not being significantly absorbed by the body. Drinking 1.6L of alum treated water a day was estimated to lead to between 0.4 and 1% lifetime burden of aluminium compared to aluminium salts in food.

If drinking alum-treated water every day causes only a very minor intake of aluminium, I'd question whether rubbing it on your face, even open cuts, would be a significant vector for additional absorbtion - it doesn't seem terribly likely.

Given aluminium is a very common metal, aluminium salts are also very common in the biosphere, so pretty hard to avoid! In very large quantities (i.e. eating it by the spoonful), aluminium salts are harmful, but there is no definitive evidence I'm aware of that they're harmful in the small quantities that are added to things such as baking powder, and used for pickling, along with the natural sources that occur up in your food-chain.

In summary; we're not convinced that normal amounts of alum in your diet is harmful, but it doesn't hurt to try and cut down on excess sources in your diet anyway. Aluminium exposure from other aluminium salt sources can be considered negligible compared to what you eat.
posted by ArkhanJG at 12:39 AM on November 27, 2012

As I understand it, the thing about Alzheimer's and aluminum is that they found increased levels of aluminum in the brains of Alzheimer's patients and people freaked the hell out over that correlation and immediately assumed that there must be a cause and effect relationship, ignoring any possibility of there being a common cause or the observation just being statistical noise and the trend not holding in larger populations.

In fact, there is some speculation now that amyloid beta plaques may not have anything to do with Alzheimer's, but might just be what your body does with excess amyloid beta, but that's beyond the scope of what you're asking.
posted by Kid Charlemagne at 1:37 AM on November 27, 2012

Best answer: The link between aluminum and Alzheimer's disease is tentative at best. Charles DeCarli, director of the Alzheimer's Disease Center at the University of Kansas Medical Center, explains:
"I believe the connection between aluminum and Alzheimer's Disease is a myth which comes from two sources:

"First, in the past, patients undergoing renal dialysis would often become confused. When renal failure occurs, the body cannot remove aluminum from the blood. In some regions, the water used for the dialysate contained a lot of aluminum. Some patients also used aluminum-containing medications. The amount of aluminum in the blood seemed to correlate with the amount of confusion the patients displayed; the concentration of aluminum in the blood of the confused patients was thousands of times higher than normal. Doctors subsequently started using purified water in renal dialysis and reducing the amount of aluminum-containing medication prescribed, which has greatly diminished the problem. When researchers realized that aluminum buildup in the bloodstream can cause confusion, they turned their attention toward the role of aluminum in Alzheimer's Disease. But the confusion associated with aluminum toxicity in dialysis patients is much different than the confusion of Alzheimer's. To date, there is no conclusive evidence that patients experiencing aluminum toxicity have a greater incidence of Alzheimer's Disease.

Second, researchers found aluminum in plaques present in the brains of people who had suffered from Alzheimer's. These plaques are associated with lesions of the brain that contain amyloid protein, which is thought to damage nerve cells and thereby cause Alzheimer's. Unfortunately, these findings were again compromised by contamination. The plaques are 'sticky'; the water used to wash the tissue to prepare for staining included some aluminum. When the tissue was processed using more sophisticated analytical methods, or when more accurate measures of aluminum content in the Alzheimer's-diseased brain were used, no excess aluminum was found. In addition, studies of the total amount of aluminum in the body of patients with Alzheimer's Disease show no increase in aluminum concentrations as compared to healthy individuals.
posted by Blasdelb at 2:12 AM on November 27, 2012 [6 favorites]

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