Icelandic Horse Connection

Success in Minimizing Summer Eczema (Sweet Itch)

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Success in Minimizing Summer Eczema (sommerekzem) (Published in October, 2003 Eidfaxi)

By: Dr. Barbara Sollner-Webb bsw@jhmi.edu, Professor, Johns Hopkins University School of Medicine, Baltimore, MD, who has two wonderful Icelandic horses in her backyard.

As probably almost all Icelandic horse owners in the US know, SE stands for Summer Exema/Excema/Eczema (alternate spellings), also called Sweet Itch. It results from an intense allergic reaction to the bites of no-see-ums, small swarming insects technically called culicoides. It occurs primarily in horses who were not exposed to these insects early in life, and it causes extreme itching, so that the horse violently scratches and bites the afflicted area. In mild cases, sections of fur are scratched off yet the skin stays mostly intact, while in more severe cases, the horse scratches and bites until the skin on the whole afflicted area is torn open and bloody. Different varieties of no-see-ums, which live in different areas of the US, preferentially bite different parts of the horse; in Maryland we have a rather wide-spread variety that attacks mainly the belly midline, also somewhat the chest, mane and face, and less so other parts of the horse.

I would like to share with other Icelandic horse owners how we have turned the terrible SE allergy of my first Icey into a quite easily manageable condition that is not too much bother for us or him. I am anxious to find out, from owners of other SE horses, if the regime we hit on that works very well for my SE Icey and for my friend's SE horse is similarly successful on other Iceys, including ones in areas with different no-see-um varieties. Further, there is hope that treating horses prophylactically may prevent onset of the allergy.

I got my first Icelandic horse shortly after he entered the US, 2 /12 years ago, and he developed a truly bad case of SE partway through his first US summer. The entire centerline of his belly rapidly became a torn-up disaster: multitudes of fresh bloody sores were continuously developing from his violent scratching of new bites before the previous bites in an area could begin to crust over. Individual sores were also appearing on other parts of his body. This bad allergy developed despite our diligent spraying with a recognized bug spray, to try to prevent an onset of SE. (However, I later learned that this particular bug spray does almost nothing against our no-see-ums, so its use provided no deterrent to his developing the SE allergy.) My reading had turned up no simple treatment to prevent the bites, short of completely covering the horse with a Boett blanket (basically a long pajama) or arranging for someone to regularly bring the Icey into a poop-free stall, ideally with a chest-high fan, for several hours each dusk and dawn; in our backyard "farm", given our work schedules, this would have been very hard to achieve. I also had read of no way to prevent the bites' intense itching, and hence their being scratched, short of massive steroid treatments to suppress the immune system.

Being an experimental scientist by profession, I decided to test different bug sprays and liniments for their effectiveness against SE. Testing bug sprays against no-see-ums is easy, since these are the insects that cluster around fresh poop piles. I was amazed to find that many standard sprays, which work well against flies, had minimal effect on no-see-ums. But fortunately, others were successful! Try the simple "poop test" yourself: divide a fresh pile into several smaller ones and spray each with a different bug spray, except a few "control" piles that remain un-sprayed, and check a few minutes later. I found that piles sprayed with Repel-X, Gnat-Away or Skin-so-soft had nearly as many no-see-ums as unsprayed ones, but piles sprayed with FlyGone 7000 had far fewer! After repeating the experiment and confirming that Flygone 7000 kept away the vast majority of the no-see-ums, we started treating the Icey with this bug repellant morning and evening, spraying mainly the belly midline but some all over, also rubbing some by hand on the face. Impressively, my Icey's SE improved!! Rather than getting so many new bites that his whole belly midline was continually scratched bloody, the skin started to crust over, punctuated by a limited number of new bloody sores. Furthermore, the number of new sores on other parts of his body also diminished dramatically. This impressive reduction in the number of new bites was very encouraging and provides the first level in a multi-barrier approach to control my Icey's SE.

So we were part way there. I then began testing various anti-itch ointments, because of course it is the itch that causes the horse's scratching and biting, which in turn makes the bloody sores. Again, you can try the test yourself, monitoring for several days how bites progress when treated with various candidate liniments. Draw an imaginary line down the center of the belly area and one running across, dividing the horse into four quadrants, and before each bug spraying, rub a test liniment on the sores of a quadrants, while leaving one quadrant without liniment. Include also the individual bites that the horse gets further up his sides. Most informative are the developing sores that you notice when the fur is partly scratched off but before the skin becomes raw or broken. I found that SWAT and Vaseline both did minimal, while Calamine helped some. Then an Icelandic friend gave me an product called Equus Lotion from the Icelandic company SDS-Smyrsl. It worked amazingly well!! This lotion clearly makes the no-see-um bites much less itchy, since the treated belly sections began to heal with a few days of treatment. Already after one treatment, the individual developing sores elsewhere on the horse looked less irritated, in contrast to untreated ones which became more abraded, generally bloody.

After figuring out an appropriate bug spray and liniment, I stopped testing other products and started treating all the afflicted areas of the horse, and his condition improved dramatically. Throughout the remainder of his first no-see-um season, this regime sufficiently reduced the new bites and their itching so that only quite sporadically did new bloody sores develop. The old sores healed, and his belly centerline grew continuous new skin for the first time in many weeks. When it first turned hot and buggy the next summer, my Icey's second in the US, his SE started again. But this time we were ready and immediately resumed the routine of twice daily spraying with FlyGone 7000 and dabbing any starting sores with SDS lotion. He still got some bites, and scratched some, but generally none formed bloody sores, and he retained much more mane than the previous year! But on occasions when treatment got lax, sores rapidly developed, so we knew the regime was working. That fall, fur even started to grow on his belly again, which had remained bald scar tissue the previous winter.

My Icey's third US summer, 2003, was far better still. Most of the time, he needed only the Flygone to prevent any SE sores. And when a sore occasionally started to develop, a single application of the SDS lotion usually gave sufficient relief that it healed. This impressive improvement might suggest that Icey is becoming somewhat tolerant of the no-see-ums. However, I suspect it is in large part due to his having learned to minimize contact with these bugs. Specifically, each dusk and dawn, when the no-see-ums come out en masse, he leave his equine buddies in the field and walks into the barn, where there are far fewer of these insects! And after a few hours, when the no-see-ums have dissipated, he goes back outside. He certainly has learned to make good use of his free access to the barn and field.

In summary, we have hit upon a multi-barrier approach to minimizing SE: First is a bug spray that is effective at greatly reducing the number of no-see-um bites. Second is a liniment that greatly reduces the itching at each bite which gets through that first line of defense. Finally, an additional valuable line of SE defense is having the horse indoors at dawn and dusk, when no-see-ums are most active, in a poop-free breezy area. Since our schedules did not permit bringing Icey in at these times, this brilliant fellow learned to do it for himself.

Let me note a few additional points: First, while the SDS Equus Lotion seems nearly magical, it isn't sufficient alone. Without an effective bug spray to reduce the vast number of no-see-um bites the poor Icey gets, a little scratching at each bite adds up to a lot of total scratching and still a bloody belly. Second, since bug spraying is new and scary to many imported Iceys, you may have to teach its acceptance; easy is to start by spraying water (so no smell) and reinforce using lots of treats. Third, no-see-ums are smaller than the mesh on most flymasks, so you need to apply bugspray to the face (but avoid the eyes and mouth; I spray it in my hand and rub that on the face). Fourth, while Flygone 7000 and the SDS lotion work very well, there certainly will be other successful products. However my experience is that most recommended flysprays and liniments seem minimally effective for SE, so test products before relying on them.

Finally, I'd like to raise an idea for new imports. Since it is well-known that the way to prevent a bad allergic reaction (like SE) is to never get a large dose of the irritant (the no-see-um bites), I suggest that immediate regular spraying with a bug spray that is effective on no-see-ums should greatly minimize new SE cases. Indeed, when I imported a second Icey a year after the first (we all know that Iceys are like potato chips and you can't have just one!), we immediately used Flygone 7000 as her bug spray. Most encouragingly, she has not developed SE! In contrast, I know ten other Icelandic horses that arrived in our general area in this same time period, and all but one developed SE already their first US summer. While certainly not statistically significant, my Flygone-sprayed horse beating these odds is very encouraging.

If your Icey has SE, or you are importing a new Icey into a SE area, I urge you to try this regime; see if it doesn't make your horse quite comfortable. He or she will certainly be very appreciative of any relief, for SE must be something like us having a bad case of poison ivy all summer long. And please, do let me know how things go with your horse's SE; my e-mail is bsw@jhmi.edu. Good luck!

[Purchase information: Flygone 7000 is marketed by Horseman's Dream and is available at many local tack stores ($15-$20/quart) or online from Valley Vet (http://www.valleyvet.com; $36.49/gallon plus shipping) or American Livestock (http://www.americanlivestock.com; $10.50/quart with free shipping on larger orders). I use about 2 gallons per Icey per summer. Fortuitously, SDS Equus Lotion has just started being imported into the US by BR Imports L.L.C. (http://www.sdsproductsusa.com; e-mail: info@sdsproductsusa.com); $21.95 for 500 ml (slightly over a pint); I used two bottles the first summer and two bottles since then.]

about myself: Barbara Sollner-Webb, bsw@jhmi.edu, is a Professor at Johns Hopkins University School of Medicine, Baltimore, MD, where she and her students study basic processes of gene expression. High on her list of favorite hobbies is trail riding, and she has two wonderful Icelandic horses in her backyard. She feels that Iceys are the perfect breed of horse, at least for a middle-aged lady who loves nature and riding and having a horse who is a real compatriot. Barbara's husband and grown daughter are also confirmed riders, although of big horses. The family also includes a delightful rescue dog (an enormous St. Bernard who sleeps on the bed) and a captivating pot-belly pig (who had been thrown out on a freeway in a snowstorm).

SE article #2:

SE is a Lesson in Immunology (Scheduled to be published spring, 2004, in Eidfaxi)

by Dr. Barbara Sollner-Webb, bsw@jhmi.edu, Professor, Johns Hopkins University School of Medicine, Baltimore, MD, who has four wonderful Icelandic horses in her backyard.

Sweet Itch (SE) is an allergic reaction to the bites of no-see-ums (technically called culicoides) and it provides a real-life lesson in basic immunology.

To better understand the affliction and to devise ways to mollify its severity and hopefully prevent its onset, lets start by reviewing a few key facts in immunology. Most fundamental, when an adult animal is exposed to a foreign protein or other biochemical ("antigen"), it generally elicits an immune response that involves developing antibodies which provide the animal with immunological protection against the invasion. However, depending on the antigen and especially on the magnitude of the initial doses, a very intense immunological response can ensue and create an allergic reaction on repeated exposure. This is the basis of SE in imported Icelandic horses.

Now, it would be disastrous if the developing immune system in a mammalian infant were to generate antibodies to molecules from its own body. So evolution has arranged that biochemicals which the baby contacts before birth and for a while after birth are recognized as "self" and do not elicit an immune response. [When this self-protection fails, it is called an "auto-immune disease".] Then for a while, until the baby's immune system is fully developed, invading antigens elicit mild immune responses but generally not the intensity for an allergic reaction.

A familiar example is chicken pox, in humans. Babies who are exposed to this virus in their first few months generally develop no obvious reaction, but when later re-exposed, they are refractory to the allergic response that we call "chicken pox". Yet without an initial exposure (or immunization, as is now available for chicken pox), later exposure almost certainly causes the allergic reaction.

With this background, SE starts to makes sense. Foals born in SE areas get bitten by no-see-ums early in life, so generally do not develop an allergic reaction. Conversely, horses imported as adults from Iceland into SE areas will have had no such early protective exposure and thus are prone to the SE allergy. It develops due to the very large number of no-see-um bites that unprotected horses can get in a single day.

Because the intensity of the exposures is important in determining whether an antigen elicits an allergic reaction, it is important to minimize the number of no-see-um bites that a horse receives. That is why bug sprays which are effective against no-see-ums can help prevent SE, even though the horse still receives some bites. It also explains the virtue of bringing SE horses inside, under fans, at dusk and dawn, when no-see-ums are the most voracious.

With this information, you may well be wondering why horses born in the US, but in an area not afflicted by SE, frequently do not develop SE when later moved into a SE area. For this, one more fact about immunology is needed, namely, that an immune response raised against a particular antigen generally provides a partial response to closely related antigens. And the US has ever-so-many more kinds of bugs than does Iceland, including various ones related to SE-causing no-see-ums. Thus, horses born in areas where they get exposed to such bugs would be much less likely to develop an allergic reaction, when brought into a SE area, than horses brought from Iceland, that did not have such an early exposure.

Now indulge me with a bit more immunology: It is known that frequent very low doses of an antigen generally do not generate an allergic reaction, but rather elicit a protective immunity. This is the principle behind desensitization shots, such as people can get for poison ivy or bee stings. Certainly this logic should extend to no-see-ums and horses. That is why my recent (October, 2003) Eidfaxi article on SE suggested that newly imported horses should religiously be treated with a bug spray that has been proven effective at markedly reducing the number of bites from no-see-ums. It will be important to spray every single day that the horse might be exposed to those bugs, for a good long period, so that the horse never receives a large number of no-see-um bites until after its immune system has been desensitized to this antigen, which fortuitously should result from the limited number of bites that the horse will receive despite the bug spray. [I suggest using FlyGone 7000 in the AM and PM throughout their whole first spring/summer/fall in the US, and in their second year at least the spring and part of the summer, and then to use this spray as their forever insect repellent.] Should the new, long-lasting bug treatments prove to be similarly effective against no-see-ums, they should simplify this treatment considerably.

By considering the immunological basis of SE, we have already found a regime that largely alleviates the allergic symptoms in my first imported Icey, who had developed a terrible case of it during his first US summer. Hopefully the above-suggested desensitization protocol can help prevent the onset of this very nasty affliction in most imported Iceys.


Added note:

An exciting-looking product called "FLY_BAN HORSE SPOT-ON" was advertised in the spring 2004 "Country Supply" catalog that it "Kills and repels members of the Culicoidae and Simuliidae vectors that may cause Sweet Itch... especially useful on horses turned out to pasture." However, the manufacturer told me they have temporally pulled this product, to re-word their packaging and advertising, for tests have shown it is no more effective against SE than standard Permethrin-containing spot-ons.

Another product that may help with dermatitis: M-T-G http://www.shapleys.com/

The following are notes and suggestions from the Icelandic Horse email list, and there are a couple of links for additional information below:

The best coal tar shampoos are the ones sold through the catalogs like Omaha Vaccine or Jeffers or one of the companies that supply dog grooming needs. Look for shampoos that talk about being anti-seborrheic(sp.). Some people believe that excess seborrhea (waxy substance secreted by the skin that blocks the pores) contributes to summer eczema type reactions. It seems to help horses that have various kinds of itchy reactions.

Whoever it was that posted this recipe said it was very close to the same ingredients of a product called "The Missing Link". It is as follows:

1 pound of Kelp (Granulated)
1.5 cups Nutritional Yeast
1.5 cups Shave Grass or Horsetail
2 cups Cattle Minerals
3/4 cup Ground Flax Seed

Also mix in for added flavor and nutrients, Raspberry Leaves - Milk Thistle - Burdock Root. I believe it was the Flax Seed that is most important in helping the body with eczema. I'll let you know how we do this summer. I've got two that suffer slightly aroung the face and belly mostly. We are also going to use the Boet Blanket this summer. So far we are just using the Hood and Belly Band while in pasture.

Flax Seed needs to be ground (some say and cooked, other say no need to cook).

Flax Seed oil is not as potent as the seed.

Linseed comes from flax plants (genus Linum), so linseed is flax seed. It's rich in phosphorous, and is a relatively good source of B group vitamins, the oil puts a nice gloss on a horse, and it's a useful feed for a lean animal.

VERY IMPORTANT: Linseeds contain the enzume linase, which when the seeds are soaked releases hydrocyanic acid (prussic acid) from a glycoside present in the seeds. Hydrocyanic acid is toxic, and although the linase should be inactivated by stomach acids, it's important to store the seeds properly so they aren't damp, and never feed it if it's been soaked but not cooked. It's also important to make sure that any linseed oil, and the left-overs (linseed meal) that you're feeding is food grade quality - low temperature oil extraction can leave linase functional.

I've always fed it cooked - it absorbs large amounts of water, and forms a thick jelly or soup that most horses seem to like (smells horrible to me). I've never used psyllium on my horses (in fact prior to being on this list I'd never heard of it's use in horses), but the jelly formed by cooking the linseed is because of the large amounts of mucilage it contains, which acts as an excellent internal lubricant. I also feed quite a bit more than a tablespoon, but not as much as some of my UK friends who feed up to a pound a day per horse. To cook it, I put about 4oz of seeds in a large heavy pot about half full of water, bring it to the boil, boil it hard for a few minutes, and then let it simmer for at least half an hour (preferably an hour or more for a nice thick gooey mix). It's a bugger for sticking and burning, so you'll need to stir it occasionally. You can mix the hot stuff with pelleted feeds or bran to form a mash that ill horses seem to enjoy.

When I first started using this recipe he had no hair on one side of his tail. The hair is starting to regrow gradually. It is also brilliant for soothing the areas where he is very sore from rubbing. The recipe is:

5 drops lavender- Boots the Chemist
5 drops Tea Tree- Boots the Chemist
2 drops Roman Camomile- Aromatherapist
2 drops Yarrow- Aromatherapist
2 drops Garlic (had to buy garlic capsules and take the oil out-) Holland and Barrett

Add these to 50ml of Aloe Vera gel (I have used a make called Banana Boat from Superdrug) and apply to the affected area twice a day for no more than 3 weeks. Emily

Possible Benefits of Flax Seed:

The supplementing of flax seed oil will help with many conditions including:

  • *clear up skin conditions
  • *relieve arthritic and inflammatory pain
  • *increase bone strength
  • *improved skin and coat condition (decreased dandruff and a beautiful shine on their coats! Even some dappling)
  • *When a pregnant mare was fed flax, her offspring were larger, and grew faster than when previous to being fed flax
  • *within 9 months cracked hooves were completely healed
  • *research indicates that horses fed flax and injected with the deadly organism Escherichia coli were better protected than those not fed flax, suggesting enhanced immunity in these animals
  • *Valuable source of energy (great to feed during the cold months or during times of stress to prevent weight loss)
  • *keeps less desirable saturated fats mobile in the blood stream
  • *increases oxygen uptake to the cell
  • *decreases recovery time from strenuous exercise
  • *Numerous studies conducted on animals and humans show that flax has powerful anti-tumor properties and may reduce tumor size by 50%.

Ellen's Spray for Sweet itch & Mosquitoes

2 oz. Permethrins
1/2 cup skin so soft (avon)
1/4 cup of Nolvasan (Fort Dodge)
2 Tbsp. Nolvasan Scrub (surgical scrub by Fort Dodge)
Water Mix all of this together in a gallon milk jug (clean one) and spray nightly of the horse. It helps fight bacteria and skin problems as well as working to defray the bugs. Since I have put this together my mare is doing great and looks great.

I spray this nightly on all the horse because I am afraid it might start in any of them, so I use this as a deterent. I have tried everything else on the market for sweet itch and nothing has worked as well as this concoction. If I miss using it for one night the mare shows signs that she is itching, so I don't miss a night. This is my own recipe so use at your own risk. But I have talked to vets and they said that everything I am using will not hurt the horse and if it works then use it. I also use the surgical scrub to wash the mare and the horses when bathing. Their coats are quite beautiful.

This year the SE has been much less a problem for my horse (his third summer with it). I think the ground flax has helped a great deal and I've reduced the amount of flax I was feeding to 1/3 cup 2X day. Also have him on a mineral supplement made especially for our geographic area and also give a homemade version of Missing Link daily. Swat applied liberally on the underside of the body (a big trouble area for him) is very helpful and liberal spraying with Clac 86. So far no mane or tail rubbing and just a few areas of the body that have a fungus-like appearance. I have been applying a zinc based preparation to these areas that I bought at Equitana this year. I guess it's a matter of alot of experimentation until you come up with something that works for your horse.

We have had a very hot, humid summer. My horse was clipped in April and grew his usual summer coat back, which is longer and thicker than I would like it to be for his comfort in the heat. His SE flared up in June and I got a fly sheet with a large belly band while at Equitana (the area where he happens to get alot of sores). It's not a Boett. As he was very hot under the mesh fly sheet, I decided to body clip him again so he would be more comfortable while wearing the sheet.

Within 5 days of being body clipped and wearing the fly sheet he was free of any new outbreak of SE and the old sores were healing fast. Now everything is completely healed and there is not a sign of any more SE. He had had a small amount on his face, spots on both sides of his barrel, alot on the chest area and belly. The mane and tail for some reason had not been too badly rubbed this year. New hair is now growing in the bald spots. The really neat thing is that the sheet has been off for over a week now and STILL no sign of SE. I fully expected it to come roaring back when I removed the sheet. We will now wait and watch to see what happens. Perhaps body clipping the summer coat off and reducing sweating is a help for him -- has anyone else had this experience? We are still in the worst part of the season for SE, but I am encouraged.

From: Konstanze Ehlebrecht

"Stroppel, Jasmin" schrieb:

I read an interesting notice in a German horse magazine today. A German breeder and importer of Icelandic horses claims, he has a way to test out in Iceland, if a horse gets sweet itch or not. He let them give an injection of a drug (can't remember the name, but can find out) which lets the horses sweat very much within a few minutes. He says, those horses which don't sweat very much after this injection are disposed for sweet itch and that he has a hit rate of 90% (There was unfortunately no declaration what is meant: only 10 % of the tested for "good" horses get sweet itch which won't be a hit rate of 90 % if usually you have a rate of 20-25%, or if 90% of the tested for "bad" horses get it)

He explains this fact with a much bigger disposal for sweet itch of horses with less sweat glands. A fact which is helpful in Iceland not to get a cold > or even pneumonia is a disadvantage in warmer an more humid climate. Of course he does not deny that the midges are the trigger of the allergic reaction, but the disposition is given by the lesser sweat glands.

I only have one horse with mild symptoms and I can not say that Sörli is sweating less than others. So for me it is hard to try to prove this theory on the living objects. How about you others have you made any observations which may support this theory?

Of course it would be very helpful to identify such horses in Iceland and not to export them, which save a lot of sorrow and pain to owner and horse.


Liebe Jasmin, ich bin froh, daß Du Dich dazu geäußert hast! Ich habe diesen Artikel auch gelesen (er war, glaube ich, im "Islandpferd") habe aber die Zeitschrift noch nicht wieder gefunden. (Meine Zeit ist leider in den letzten Monaten in hauchdünne Scheiben geschnitten :((( Ich finde diese Info sehr interessant, hatte aber die selben Schwierigkeiten mit der Interpretation von "90%" wie Du. Hatte mir auch vorgenommen, den Autor mal dazu zu befragen. In unserer kleinen Herde in Island haben wir eine Stute, von der ich glaube, daß sie S.E bekommen würde, falls exportiert. Möglicherweise könnte ich das an dieser Stute mal ausprobieren, obwohl ich etwas zögerlich bin, nur so "zum Spaß" mein Pferd mit einer Substanz zu traktieren, nur um meine Neugier zu befriedigen!

Auf jeden Fall gehört zu einer Allergie neben dem auslösenden Faktor aber auch noch die Disposition und warum sollte dieser Umstand nicht ebenfalls begünstigend wirken. Auch "Disposition" ist ja kein absoluter Faktor sonder kann sich auch aus mehren Teilfaktoren zusammensetzen. (Halt mich bitte nicht für spinnert, aber da beim Menschen ja auch das psychische Strickmuster eine Rolle spielt, hatte ich auch schon mal überlegt, Besitzer von Ekzemern zu fragen, welche Position in der Hierarchie der Herde ihre Tiere einnehmen.)

Liebe Grüße in die Schweiz,

Konstanze in Köln

I make a rinse, pour over areas that are really making him itch. Making sure it gets down to his skin. Do not rinse out. Take an inch of fresh rosemary, inch of fresh mint, put it in 4 cups of boiling water, let it steep until lukewarm, take herbs out, add 1/4 cup good white vinegar. Do this about once a week.

In my experience, once a horse experiences sweetitch, it comes back every year and tends to get worse.

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Input the words "summer eczema" or "sweet itch"
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