Re: Nair to soften nails

Jean (not otherwise identified) asks about using Nair to soften paraffin 
blocks, a topic that has been discussed here before.

About ten years ago I did a locum tenens in a laboratory (the names have been 
changed to protect the guilty) that used Nair extensively. In those distant 
days pathologists occasionally wrote procedures, and I wrote this procedure 
for them because they didn't have one. I've left the procedure mostly 
unchanged so that readers can understand the context in which Nair was used.

Bob Richmond
Samurai Pathologist
Knoxville TN
PRINCIPLE: Nair, a proprietary depilatory, is used to soften paraffin blocks 
before cutting sections.

SPECIMEN:  In this laboratory neutral buffered formalin is used, followed by 
processing without vacuum through an aliphatic xylene substitute into a 
proprietary embedding compound.

REAGENTS:  Nair lotion hair remover with baby oil. Ingredients: water, 
mineral oil, calcium hydroxide, sodium thioglycolate, cetearyl alcohol, 
calcium thioglycolate, ceteareth-20, fragrance, and iron oxides (July 1991). 
Carter Products, Division of Carter-Wallace, Inc. New York NY 10153.

INSTRUMENTATION:  Open processor without vacuum. An electric fry pan is used 
in lieu of an embedding station. Paraffin microtome.


1. Cut paraffin block down to desired level with a microtome.
2. Remove from microtome.
3. Smear on Nair at room temperature
4. Let sit at least 5 minutes, but not more than 15 minutes.
5. Wipe the Nair off.
6. Replace paraffin block in microtome and cut sections 

RESULTS:  Paraffin embedded tissue is softened and is easier to cut. 
Supposedly this effect is the result of the keratolytic action of the 
depilatory (thioglycolate) but it seems equally likely that the softening is 
the result of penetration by mineral oil. The effect of this technique on the 
results of immunoperoxidase stains is unknown.

NOTES: This procedure is done on all paraffin blocks at Cloudcuckoobury 
Laboratories, Nephelococcygia. The procedure did not originate in this labor
atory. It adds about a minute to the time of cutting a paraffin block (4.5 
CAP work units/BLOCK without it). 

Lee Luna (see reference in the old AFIP manual, page 119) used the depilatory 
lotion NeetŪ for softening keratin. He placed the formalin-fixed specimen in 
the depilatory solution for several hours, then checked to see if it would 
bend easily. He washed the specimen in running water 10 minutes, and 
processed. Formalin fixation keeps the depilatory from entirely dissolving 
the keratin.

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