7 Things you may not have known about DMSO

This odif­er­ous com­pound has be­come a com­mon treat­ment for a va­ri­ety of in­flam­ma­tory con­di­tions. Here are a few in­ter­est­ing facts about its his­tory and ac­tion.

EQUUS - - Contents - By Chris­tine Barakat

This odif­er­ous com­pound has be­come a com­mon treat­ment for a va­ri­ety of in­flam­ma­tory con­di­tions. Here are a few in­ter­est­ing facts about its his­tory and ac­tion.

Two decades ago, if you men­tioned dimethyl sul­fox­ide (DMSO) around the barn you may have got­ten puz­zled looks in re­sponse. Back then, this in­dus­trial sol­vent turned an­ti­in­flam­ma­tory ther­apy was rel­a­tively new to the horse world, and even if peo­ple had heard of it they viewed it as an un­usual or even mys­te­ri­ous op­tion.

Since then, DMSO has gone main­stream. It is ap­proved by the Food and Drug Ad­min­is­tra­tion (FDA) for top­i­cal use on horses, but vet­eri­nar­i­ans reg­u­larly use the chem­i­cal “off-la­bel” in other ways to treat a wide ar­ray of in­flam­ma­tory con­di­tions, from lamini­tis to neu­ro­log­i­cal prob­lems. When the DMSO’s dis­tinc­tive gar­licky smell wafts through the barn th­ese days, peo­ple are more likely to nod know­ingly than won­der what's go­ing on. None­the­less, DMSO is a lit­tle like as­pirin—some­thing that many peo­ple use with­out nec­es­sar­ily think­ing too much about how it works. But learn­ing more about DMSO may help you ap­pre­ci­ate how it can be use­ful in main­tain­ing your horse's health and com­fort. So here are seven things you might not know about DMSO. use with­out nec­es­sar­ily think­ing


A byprod­uct of pa­per pro­duc­tion, DMSO was first de­vel­oped as an in­dus­trial sol­vent. As peo­ple worked with the chem­i­cal, they no­ticed that if they spilled a bit of DMSO on their hands a dis­tinct gar­licky taste would be on their tongue shortly there­after. This in­trigued chemists, who be­gan re­search­ing how the liq­uid could so quickly pass through skin and mu­cosa, but the work was gen­er­ally lim­ited to ex­plor­ing non-med­i­cal ap­pli­ca­tions.

Then, in the 1960s, Stan­ley Ja­cob, MD, be­gan in­ves­ti­gat­ing DMSO as a preser­va­tive for or­gans des­tined for trans­plants. Work done in his lab­o­ra­tory soon sparked a rush of re­search into DMSO’s pos­si­ble med­i­cal uses.

By 1965, how­ever, the FDA closed down clin­i­cal tri­als cit­ing safety con­cerns. Since then, DMSO has been ap­proved for some spe­cific ap­pli­ca­tions. In hu­man medicine, th­ese in­clude use as an or­gan preser­va­tive and as treat­ment for a blad­der dis­ease called in­ter­sti­tial cys­ti­tis. In 1970 it was ap­proved for top­i­cal use in horses and dogs.


DMSO is clas­si­fied as a non­s­teroidal anti-in­flam­ma­tory drug (NSAID), just like phenylbu­ta­zone (“bute”). Un­like bute, how­ever, DMSO con­trols in­flam­ma­tion pri­mar­ily by act­ing as an an­tiox­i­dant.

You may be more fa­mil­iar with an­tiox­i­dant sources in nu­tri­tion, such as vi­ta­min E or ly­copene, but DMSO has a molec­u­lar struc­ture that al­lows it to func­tion in the same way. Specif­i­cally, DMSO binds with “free rad­i­cals,” which are oxy­gen com­pounds---left­overs from nor­mal bio­chem­i­cal re­ac­tions---that dam­age or de­stroy healthy cells. Th­ese free rad­i­cals are of­ten the byprod­uct of in­flam­ma­tion and, in turn, cause more swelling and in­flam­ma­tion as they ac­cu­mu­late. DMSO is a free rad­i­cal scav­enger that slows or halts this process.

When used to con­trol in­flam­ma­tion in strains and other soft-tis­sue in­juries, DMSO is usu­ally ap­plied top­i­cally.

How­ever, it may also be in­jected into a tar­get area when an in­jury oc­curs in par­tic­u­larly dense tis­sue, such as a bowed ten­don, or the site is dif­fi­cult to reach. A vet­eri­nar­ian may ad­min­is­ter DMSO orally or in­tra­venously in the early stages of lamini­tis to try to slow or halt the in­flam­ma­tory cas­cade.


DMSO is a hy­gro­scopic com­pound, mean­ing it at­tracts wa­ter. This prop­erty makes the com­pound es­pe­cially ver­sa­tile. For in­stance, it can re­duce edema0 in swollen limbs and is of­ten used as part of a “sweat” to com­bat stock­ing up. DMSO can also re­duce swelling in the brain and spinal cord, which can be lit­er­ally life­sav­ing in dis­eases like West0 Nile en­cephali­tis. DMSO may be used to draw flu­ids out of the lungs in cases of acute pul­monary edema.

Be­cause it pulls wa­ter from tis­sues, DMSO has a di­uretic ef­fect, mean­ing it makes a horse uri­nate more. This can help flush tox­ins from the body more quickly. With this ac­tion in mind, DMSO is of­ten given in­tra­venously in the treat­ment of can­tharidin poi­son­ing (blis­ter bee­tle tox­i­c­ity), to lessen the ef­fect of the toxin on the kid­neys and in­testi­nal tract. Af­ter episodes of ty­ing up, DMSO may help horses elim­i­nate waste prod­ucts of mus­cle break­down through their urine more quickly. The di­uretic ac­tion of DMSO, how­ever, can make it un­safe for horses who are dehydrated or in shock. It can fur­ther de­hy­drate th­ese an­i­mals or dan­ger­ously lower their blood pres­sure.


DMSO’s molec­u­lar struc­ture al­lows many sub­stances to dis­solve com­pletely within it. It also al­lows the chem­i­cal to transport th­ese dis­solved sub­stances through cell mem­branes with­out dam­ag­ing them, even if th­ese sub­stances wouldn’t be able to pass through on their own.

For in­stance, treat­ing rain­rot or other skin in­fec­tions can be dif­fi­cult be­cause the re­spon­si­ble or­gan­isms are buried deep un­der the skin or crusty, painful scabs. How­ever, a mix­ture com­bin­ing an­tibac­te­rial med­i­ca­tion with DMSO can pass through the skin and reach the af­fected area. For the same rea­son, DMSO is of­ten added to an­ti­fun­gal med­i­ca­tions for treat­ment of eye con­di­tions and some­times to steroids for tar­geted, top­i­cal anti-in­flam­ma­tory treat­ment.

It’s im­por­tant, of course, to avoid in­ad­ver­tently mix­ing DMSO with po­ten­tially toxic sub­stances. You wouldn’t want fly spray cross­ing into your horse’s blood­stream, for ex­am­ple, so take care to avoid ap­ply­ing DMSO to your horse if he has re­cently been sprayed. Like­wise, avoid mix­ing DMSO with sub­stances that could be toxic if in­gested, such as organophos­phates or mer­cury salt. Also be mind­ful that the ef­fects of some drugs, such as cor­ti­cos­teroids and at­ropine, are in­ten­si­fied when mixed with DMSO, so do­ing so needs to be done with cau­tion un­der a vet­eri­nar­ian’s di­rec­tion.


Although it’s com­monly mixed with com­pounds to pro­vide pain re­lief, some stud­ies sug­gest that DMSO alone has anal­gesic prop­er­ties. Re­search shows

that DMSO slows or blocks con­duc­tion of im­pulses along nerve cells, which in ef­fect re­duces pain from mus­cu­loskele­tal in­juries, post­op­er­a­tive in­ci­sions and other sources. Re­lief is only tem­po­rary ---last­ing up to a few hours---be­cause as the DMSO dis­si­pates, nor­mal nerve func­tion re­turns. It can be com­bined with other pain-re­liev­ing drugs, how­ever, to ex­tend the anal­gesic ac­tion.

If it seems like DMSO has a va­ri­ety of pur­ported ac­tions, that’s true. It’s noth­ing if not ver­sa­tile. Some ap­pli­ca­tions of DMSO com­bine all of th­ese: For in­stance, it is of­ten used in sur­gi­cal colic cases to re­duce the risk of tis­sue ad­he­sions due to in­flam­ma­tion and poor cir­cu­la­tion; some sur­geons think that it may also pro­vide some pain re­lief in the hours fol­low­ing surgery.



DMSO isn’t tech­ni­cally a med­i­ca­tion, but var­i­ous com­pe­ti­tion or­ga­ni­za­tions treat it as one when it comes to drug test­ing.

The Fédéra­tion Equestre In­ter­na­tionale (FEI) clas­si­fies DMSO as a “con­trolled” pro­hib­ited sub­stance, mean­ing that although it may have some ther­a­peu­tic value, DMSO has the po­ten­tial to af­fect a horse’s per­for­mance and its use is for­bid­den or lim­ited. As of Jan­uary 2018, the threshold of DMSO al­lowed by FEI was 15 mi­cro­grams per mil­li­liter in urine or one mi­cro­gram per mil­li­liter in plasma. The Jockey Club al­lows 10 mi­cro­grams per mil­li­liter of plasma. If you com­pete with your horse, check any gov­ern­ing as­so­ci­a­tion rules re­gard­ing DMSO use.

Also keep in mind that be­cause DMSO can move other ma­te­ri­als through the skin, com­bin­ing it with other med­i­ca­tions could re­sult in a vi­o­la­tion of thresh­olds for both. For in­stance, mix­ing DMSO with the top­i­cal NSAID Sur­pass (di­clofenac) can cause an in­crease of the med­i­ca­tion in the blood­stream, lead­ing to a dis­qual­i­fy­ing test. The med­i­ca­tion guide­lines for the United States Eques­trian Fed­er­a­tion state, “Do not ap­ply di­clofenac cream in com­bi­na­tion with any other top­i­cal prepa­ra­tions in­clud­ing DMSO, ni­tro­fu­ra­zone, or lin­i­ments.”


A search of a re­search data­base will turn up a good sam­pling of peer­re­viewed pa­pers on DMSO use in horses, but the com­pound has got­ten far less sci­en­tific scru­tiny than have med­i­ca­tions de­vel­oped specif­i­cally for ther­a­peu­tic ap­pli­ca­tions. Some stud­ies about DMSO’s ef­fects con­tra­dict each other, par­tic­u­larly in re­gard to its use for treat­ing arthri­tis.

Scant in­for­ma­tion is avail­able re­gard­ing dos­ing. Of­ten vet­eri­nar­i­ans rely on their own ex­pe­ri­ences and those of their col­leagues in de­cid­ing when and how to use DMSO. That is why it’s im­por­tant to let your vet­eri­nar­ian lead the way when it comes to treat­ing your horse with this com­pound.

het­her ap­plied top­i­cally, Wo­rally, in­tra­venously or by in­jec­tion, DMSO re­quires care­ful han­dling. But its ver­sa­til­ity means that if you haven’t used it so far, you prob­a­bly will even­tu­ally. If you do, keep th­ese ba­sic facts in mind to make sure your horse ben­e­fits fully from this un­usual prepa­ra­tion.

DMSO can dra­mat­i­cally re­duce edema in swollen limbs and is of­ten used as part of a “sweat” to com­bat stock­ing up.

Although DMSO isn’t tech­ni­cally a med­i­ca­tion, it is treated as one when it comes to test­ing by var­i­ous com­pet­i­tive or­ga­ni­za­tions.

A mix­ture com­bin­ing an­tibac­te­rial med­i­ca­tion with DMSO can pass through the skin and reach the area af­fected by rain­rot.

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