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Citronella oil safe for horses?

From: Carol

Dear Jessica, it has been so hot this summer and the bugs are driving all of us (people and horses) crazy. I can't find any fly spray that works for more than a few hours, and it's not only the flies. We have mosquitos that bite horses and people, and we have ticks (which scare me to death because of Lyme disease) and other biting bugs too.

I asked my farrier what she would recommend and she named a couple of products but I had tried both of them and they don't work for me. So I asked her to recommend something else and she said that she had heard of using apple cider vinegar and salad oil and citronella oil, mixing them and shaking them up and using them on the horses. I tried this and my horse reacted very badly, he got swollen up wherever I had sprayed him, and his chest and the underside of his neck looked all blistery. I don't know whether I got the mix wrong or what I did wrong, but it took a week before my horse was feeling better and the swellings went back down. I know that salad oil won't hurt a horse's skin and I'm pretty sure that cider vinegar won't either, but a lot of people have told me that they make their own bug sprays with citronella oil or some other kind of oil (I can't think of any of the names right now) and I haven't heard of anybody's horse (or any person) getting swollen and blistery like Chieftain. Can you give me some information about this? I don't understand how the citronella could be a problem because it's a natural oil, isn't it?


Hi Carol! Oddly enough, you are the third person this week to ask a question like this. I expect the bugs are out in force in a lot of different parts of the country.

This one really falls into the "talk to your vet" category, and I hope that you WILL consult with your vet about the blisters on your horse, and that you will also ask your vet's advice before you mix up any more home-made flyspray. Not only will your vet be able to tell you whether the "recipe" you plan to use has any individual ingredients that could hurt your horse, s/he'll also be able to tell you whether the COMBINATION of ingredients could hurt your horse. Not all mixtures are safe - which is why it's also a very bad idea to create home-made "mixtures" of several commercial fly sprays... the results can be extremely unhealthy for horses. So - TALK TO YOUR VET! Meanwhile, I can tell you what I know about the specific items you've mentioned.

Cider vinegar is unlikely to hurt your horse, whether you use it as a topical application or add it to your horse's feed. The same thing is true for salad oil. I'm not sure that salad dressing (vinegar and oil, yes?) will be much help against biting insects, but it's very unlikely to cause blistering... which is more than I can say for the third ingredient in the mix you've described.

I can think of two different things that may have gone wrong, and both of them involve the citronella oil.

First, I know that someone is circulating a very dangerous "recipe" for home-made flyspray. I know this because over the last few months, at least a dozen people have sent it to me. The recipe includes apple cider vinegar, dish detergent, bath oil, and citronella oil - and (this is where it become VERY dangerous) it SPECIFIES "citronella lamp oil for tiki torches".


There are two products called "citronella oil". One is the actual essential oil, "100% pure citronella oil". It is distilled from lemon grass, and has a distinctive, lemony smell. This is a plant product (but don't use it on your horse either, at least not until you've read the next paragraph and talked with your vet). The other product advertised as "citronella oil" is an inexpensive petroleum product with "citronella smell" added. The essential oil may cost you $5 or $6 for a tiny bottle containing one or two ounces; the same money will buy you a large container of the petroleum product... but they are NOT the same.

So, now you know to avoid using the petroleum "tiki torch" or "outdoor lamp" product on your horse - but there's something else you need to know. Talk to your vet about whether the essential oil (that's the expensive, plant product in the small bottles, remember) is safe to use on your horse's skin. IT MAY NOT BE SAFE, for two reasons.

Reason One: Citronella oil can be photosensitive - and your horse may end up being badly burned by sunlight that would not normally cause him any problems at all.

Reason Two: Some horses (like some humans) are sensitive to certain oils. Some are VERY sensitive to certain oils. If your horse is sensitive to citronella oil, and you use it on his skin, he may do exactly what your horse did - swell up and blister, even if he is nowhere near any sunlight. This is very painful, and can be dangerous. If it happens again, get your vet out as soon as possible. Getting an allergic swelling like this to recede may require anything from antihistimines to steroids, and it may also involve YOU doing a lot of cold-hosing and hand-walking. You and your horse will definitely need help from your veterinarian.

TRY PATCH TESTING. If you've ever coloured your hair, or if you've even READ the instructions on a packet of hair colouring product, you probably noticed the paragraph that warns you NOT to use the product until you have tested a tiny amount of it on your arm or some other area where a reaction would be noticeable but not horribly painful or inconvenient. This is a very sensible precaution, and you should do much the same thing when you buy or mix any flyspray product for your horse. Pick a spot on the side of his neck, or on the side of his rump, and apply a small amount of the product there. Wait eight hours and check the spots. If there's been no reaction at all, then you can probably use the product. If there IS a reaction - a swelling or blister - call your vet (and dispose of the spray so that nobody else can mistakenly use any of it on your horse).

By the way, this is useful advice for any product you apply to your horse's hair and skin. Please be careful with whatever you use, don't mix products, and beware of accepting advice about home-made mixtures. I've heard of people using all sorts of essential oils, undiluted (never a good idea!), in their home-made fly sprays - along with other substances such as Pine-Sol, Lysol, DMSO... THIS IS A VERY BAD IDEA.

Even if your horse doesn't show an initial reaction to whatever it is you plan to use, get your vet's approval before you use it, and then be careful when using it, and be careful the NEXT time you use it, and the time after that... Horses, like humans, can develop sensitivities to just about anything, so if your horse reacts by swelling up, sloughing skin, or showing wall-to-wall welts the second or third time you use ANY product (commercial product or home-made mixture), STOP using it, call your vet, explain what happened and find out what you should do and how you can remove the product quickly without doing more damage.

I know that it's very frustrating to see your beloved horse being driven mad by biting insects. I also realize that horses can have bad reactions to insect bites! But with many of these bizarre mixtures of this and that, the "treatment" may be more dangerous than the biting insects. Fly spray is a necessary evil, it can be quite expensive, and most horse owners are constantly changing brands and searching for a product that will really work well on their horses. Of course it's tempting to experiment with mixtures that someone - known or anonymous - offers to "share", and "home made" sounds so much friendlier and safer than "commercial, chemical product" - but it's less tempting when we remember that EVERYTHING is made of chemicals, and that by mixing some of THIS with some of THAT and a bit of THE OTHER, we could be cooking up something that will put our horses at risk. With flyspray, just as with so many other products, "natural" and "home-made" are not syonyms for "safe".

There's a place for essential oils in the home and in the barn, but anyone who uses them should buy them from a reputable source and use them carefully. It's important to remember that (a) essential oils should always be diluted with a carrier oil, (b) only tiny amounts should be used, and (c) not all essential oils are of the same quality and purity. It's also important to read EVERY label carefully - as you now know, there's the product called "citronella oil" for lamps, and then there's the essential oil, and they are very different... but you may need a magnifying glass to read the fine print on the label. ;-)


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