Page 106 - Journal of Special Operations Medicine - Summer 2014

Figure 2 Blister on the toe. the Marines wearing the prototype sock with the liner
(24% versus 11%) or compared with Marines wearing
the standard military sock with the liner (24% versus
9%). The polyester sock presumably removed sweat
more rapidly while the thick sock presumably reduced
friction. 3

Antiperspirants
Sweat can be considerably reduced or eliminated by us-
ing antiperspirants. In one study, an antiperspirant con-
taining 20% aluminum chloride hexahydrate, a common
ingredient in underarm deodorants, or a placebo was
studied during a road march performed by U.S. Mili-
treating the blister, you can tear off the blister roof be- tary Academy Cadets at West Point, New York. Cadets
cause the now-elevated blister area will still be subjected applied the preparations to their feet at least three con-
to shearing forces at the pressure points. 1 secutive evenings before a 21-km road march, during
which they carried a total load of about 72 lb. Twenty-
Sweat, carrying loads, and faster walking make the situ- one percent of cadets using the antiperspirants experi-
ation even worse. When you first start to walk, your feet enced blisters compared with 48% of the cadets in the
are usually dry. This initially reduces friction because placebo group. However, skin irritation was reported by
you shed skin cells that provide a dry lubrication, much 57% of Cadets using the antiperspirant but only 6% of
like graphite. However, as you continue to walk and cadets in the placebo group. This study suggests that
4
begin to sweat, the moisture holds the loose skin cells antiperspirant may be an effective method of reducing
in place because of surface tension. This increases fric- foot blisters during road marching, but many users may
tion and makes blisters more likely. With an increase in have problems with skin irritation caused by the active
load or speed of march, more forceful movement of the ingredient. It may be possible to reduce skin irritation
foot inside the boot will increase the effect of friction. by using a lower concentration of aluminum chloride
1
Greater loads may also cause the foot to expand, in- hexahydrate or altering how often the antiperspirant is
creasing the number of pressure points inside the boot. 2 used (i.e., every other night or every third night). A com-
mon sense approach is to stop using this preparation if
irritation does occur. One of the best advantages of an-
Prevention of Foot Blisters
tiperspirants is that once you achieve the antiperspirant
Proper boot sizing, foot conditioning, particular types effect (after 3–5 days of applications), you can maintain
of socks, and antiperspirants can reduce your chances of it by future applications of about once a week.
getting blisters. Blisters occur most often in feet that have
not been properly conditioned. Research studies show
that skin adapts to repeated frictional effects. These ad- Additional Information
aptations include thicker skin, more rapid replacement Army Field Manual (FM) 21-18 (Procedures and Tech-
of the outer skin layer, and improved adhesion between niques of Foot Marches) contains additional information
skin layers. Skin adaptations occur in proportion to on treatment of foot blisters, general foot care (Appendix
training. The likelihood of blisters decreases if you train C), and physical conditioning for foot marches (Chapter
with loads and over distances you expect to encounter 5). The references at the end of this article contain more
on tactical missions and exercises. 1 technical details for medical personnel.

Socks
Particular types of socks may also help. A Marine Corps Summary
study looked at three types of sock systems: a standard To avoid blisters, first and foremost, select properly sized
green combat boot sock (wool-cotton-nylon-spandex boots for your feet. Break in the boots, gradually at first,
combination), the standard green combat boot sock with ever-increasing walking or marching distances with
with a liner sock consisting of polyester (i.e., a sock that a light load. Then condition your feet through regular
“wicks” away moisture), and a prototype outer sock road marching using loads, distances, and speeds similar
consisting of a wool-polypropylene combination worn to those you expect to encounter in regular missions.
over the same polyester liner sock as that of the second Use friction-reducing socks and socks that will “wick”
system. Blister cases requiring medical attention (i.e., se- away moisture. Antiperspirants applied to the feet sev-
rious ones) occurred with greater frequency in the Ma- eral nights before a march (and repeated at least once
rines wearing the standard military sock compared with a week) will also help, but if you experience irritation

96 Journal of Special Operations Medicine Volume 14, Edition 2/Summer 2014