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My wife was just at a grocery store and a checkout girl told her that calamine lotion (zinc oxide + ferric oxide) had been correlated to kidney failure. My wife was going to get it for my daughter who has some mosquito bites and this checkout girl's statement caused her to get some far more expensive clay stuff instead.

This just sounded absolutely absurd to me, so I thought I'd ask about it here.

In my searching, I can't find any references elsewhere to calamine (or caladryl, its other name) and kidney failure. About the only thing I can turn up is a connection between cadmium and kidney failure, such as this quote from Medicine Plus, a service of the US National Library of Medicine:

Note that many zinc products also contain another metal called cadmium. This is because zinc and cadmium are chemically similar and often occur together in nature. Exposure to high levels of cadmium over a long time can lead to kidney failure. The concentration of cadmium in zinc-containing supplements can vary as much as 37-fold. Look for zinc-gluconate products. Zinc gluconate consistently contains the lowest cadmium levels.

Calamine, however, is zinc oxide, not pure zinc. It's not clear whether or not zinc oxide containing products suffer from the same potential risk of cadmium contamination as those containing pure zinc.

Nothing from Wiki on zinc toxicity stands out to me as supporting this, nor does this page from Medicine Plus on zinc oxide overdoses.

Is there any evidence that calamine lotion (aka caladryl) contains anything that might be positively correlated with kidney failure from moderate topical use?

It's hard to qualify "moderate"... I have used it less than 10 times in my entire life. The most was for chicken pox and perhaps some bug bites when I was a kid.

Let's cap usage as topical application to the skin in approximately 2.5cm diameter blots applied to 10 spots on the body for three consecutive days and doing this once per month. Doing an insanely rough calculation, if the application coating thickness is 0.5mm (pretty darn thick, in my opinion), this would be (pi x 2.5cm^2 x 0.05cm) x 10 spots x 3 consecutive days x 12 months = 141.3 cm^3 / 141.3 mL / year applied topically.

Hendy
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  • Zinc oxide creams are used directly for nappy rash and as heavy-duty sunscreen. What percentage of calamine lotion is zinc oxide? – John Lyon Aug 01 '11 at 01:06
  • @jozzas: I haven't found a reference giving me the portion of Zn oxide... Wiki only mentions the % of ferric oxide. – Hendy Aug 01 '11 at 01:34
  • The "zinc oxide, not pure zinc" reasoning is flawed. Cadmium and zinc occur together in nature due to their chemical similarity, but not as pure metals. So, if anything, non-refined zinc oxide is _more_ likely to contain cadmium. – MSalters Aug 01 '11 at 11:42
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    @MSalters: the reasoning would be flawed if there was reasoning present. Re-read; all I did was point out the difference between the quote and the contents, and then say, "*It's not clear whether or not...*" I never made a claim to know or a definitive statement. – Hendy Aug 01 '11 at 11:55
  • I do remember some months back about some uproar that zinc buildup was leading to kindney failure. But that went away quickly so I assumed it was less proven than they were claiming. – Chad Aug 01 '11 at 12:39

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I could not find a single supporting claim on the internet for the claim you provided so I would argue it's not notable.

Note that Calamine applied topically is not absorbed through the skin source:

Zinc oxide or calamine are unlikely to be absorbed through the skin. Zinc salts are poorly absorbed from the gastrointestinal tract. Only a small proportion of dietary zinc is absorbed. Zinc is widely distributed throughout the body and is excreted in the faeces with only traces appearing in the urine.

Possible side effects if someone were stupid enough to drink calamine lotion (source):

Side Effects If Ingested

Although it is unlikely that calamine lotion will be ingested if it is kept out of the reach of children, the lotion contains zinc oxide, which can cause an allergic reaction if swallowed. According to the National Institutes of Health, zinc oxide poisoning can occur if calamine lotion is eaten. Symptoms of zinc oxide poisoning include upset stomach, diarrhea, chills and fever, a yellowing of the eyes or skin, and irritation of the mouth and throat.

Although the above is not from a scientific article I think it is clear and logical that zinc poisoning is possible if you were to ingest a product that contains zinc.

There is no indication of what levels of zinc poisoning or zinc ingestion needs to occur before there is damage to the kidneys, but zinc poisoning will damage your organs.

There is nothing to indicate that topical use will lead to kidney failure.

There is evidence to suggest that someone silly enough could correlate kidney failure with calamine lotion purely because it contains zinc oxide.

going
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    Toxicology on ZnO from [a fact sheet](http://fscimage.fishersci.com/msds/25490.htm): *Oral* LC50 for *mice* (concentration at which half the mice are killed): 7950 mg/kg. Carcinogenicity: Not listed by ACGIH, IARC, NTP, or CA Prop 65. – Oddthinking Aug 08 '11 at 08:01