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Food allergies occur when the body's immune system is in overdrive. A normally functioning immune system detects invaders and takes steps to stop them. With allergies, the immune system mistakenly believes that something non-threatening, such as a particular food, is an invader, and mounts an attack on the offending substance. The body does this by releasing immunoglobulins, which aim to bind with the invaders and thus neutralise them. Immunoglobulins initially attach themselves to mast cells, which release histamine into the surrounding tissue. This release of histamine causes inflammation of and irritation to the tissue. Humans have a lot of mast cells in the respiratory tract, which is why allergic humans like me tend to exhibit respiratory problems; but cats also have a lot of mast cells on their skin, which is why cats with allergies tend to exhibit skin problems.
Cats may have other allergies, such as flea allergy and/or atopy (inhaled allergies which cause respiratory problems, similar to allergies in humans) - up to 30% of cats with food allergies may have other allergies too.
People often assume a novel food causes food allergies but in fact it is quite common for a cat (and for humans) to develop an allergy to a food with which s/he is familiar, and which s/he may have eaten for years with no problems.
Food allergies in cats may have a number of different symptoms, and you may see any or all of the following.
As you might expect, food allergies may affect the gastro-intestinal tract. In fact, they may actually contribute to the development of Inflammatory Bowel Disease (IBD) (which Harpsie had). Symptoms include diarrhoea, often watery or with bright red blood, and vomiting.
Another sign of food allergies in cats is "gunky" ears. The gunk is usually brown. It may improve if the cat is put on antibiotics or antifungal medications, but usually returns shortly after the medications are stopped. The cat may also have somewhat reddened ears, or they may be lacking fur from the cat scratching.
Long Beach Animal Hospital has a photo of gunky ears (these are really severe; Harpsie's were not that bad!). Scroll down to Number 3. Otitis externa.
Treating ear problems in cats, dogs and other pets is an article by Dr Roger Ross which has helpful information about diagnosing and treating gunky ears.
Vet Info has some information about ear problems.
Most cats with food allergies present with skin problems. Usually the cat is extremely itchy (pruritis) around the face and neck, and may scratch these areas a lot, resulting in sore red areas, scabs (miliary dermatitis) and fur loss The itching and scratching will be seen year round, not only in flea season.
Sometimes cats will have bald patches with no apparent problems; this happened to Harpsie. On the other hand, you may also see "hot spots", also known as acute moist dermatitis. In these cases, the cat has scratched the sore skin so much that it has become infected, making the situation even worse; Harpsie had these too. Hot spots are painful, and the infections need treating promptly.
Long Beach Animal Hospital has a photo of hot spots - scroll down to Number 3. acute moist dermatitis.
Pet Education discusses possible causes of hair loss in cats.
Your vet will examine your cat for fleas and evidence of other forms of skin or ear problems e.g. ear mites or ringworm. Your vet may also take skin scrapings to check for fungal or bacterial infection. If such problems are present, they will be treated to see if the problem is then resolved.
Bloodwork will be run - eosinophil levels are often elevated in cats with allergies.
Skin tests or blood tests for allergies may be run but these tend to more reliable for atopic (airborne) allergies.
The best way to diagnose food allergies, which happens to be a form of treatment too, is to feed an elimination diet. You can read more about this approach below. If your cat starts exhibiting symptoms again after stopping the elimination diet and returning to normal food, the diagnosis is confirmed. However, we did not bother feeding normal food again, we could see how well Harpsie was doing on the elimination diet and did not want to rock the boat.
Feeding an elimination diet may resolve the problem in the longer term, but in the shorter term you may also need to use some of the other methods outlined below in order to give your cat relief from itching and scratching.
If your cat has hot spots and infections (pyoderma), your cat will need antibiotics and/or antifungals, depending upon the cause of the infection, but chances are the infections will recur until you get to the source of the problem.
For cats with ear infections, your vet will probably also want you to clean your cat's ears.
Drs Foster and Smith have some information on cleaning gunky ears.
Treating ear problems in cats, dogs and other pets is an article by Dr Roger Ross which has helpful information about diagnosing and treating gunky ears.
Histamine is a chemical in the body which causes the itchiness, redness and swelling seen with inflammation. Antihistamines are supposed to combat the histamine and reduce these effects (though I have yet to find one which works for me and my allergies).
Cats often do not respond to antihistamines either, but one called chlorpheniramine (Clor-Trimeton) seems to be pretty effective for itchy cats, so is probably worth a try. Make sure you do not buy a brand containing acetaminophen (Tylenol) because acetaminophen is toxic to cats. Chlorpheniramine seems to work better when used in conjunction with essential fatty acids.
Mar Vista Vet has more information about the use of chlorpheniramine in cats.
Essential fatty acids are so called because the body cannot synthesise them, so they have to be obtained from food. The two main types of EFAs are Omega-3 and Omega-6. The modern diet tends to contain far more Omega-6, partly because Omega-6 EFAs are cheaper and more stable, but this may create a potentially harmful imbalance. What is the correct balance is not yet known, though some believe it is probably around 5:1 (Omega-6:Omega-3).
Essential fatty acids can help with food allergies because they have anti-inflammatory effects. The usual form of supplement is fish oil given orally, though oils from the liver, such as cod liver oil, are not ideal because they contain too much Vitamin A and D - look for an oil pressed from the flesh only. If fish oils are given, extra Vitamin E is also required in order to avoid steatitis (see Paragraph D). Flax seed oil is not recommended, because it does not contain all the essential fatty acids which a cat needs.
Essential fatty acids appear to be particularly helpful for food allergies when used in conjunction with an antihistamine called chlorpheniramine.
Pet Education provides a general overview of EFAs.
Consumer Lab has a summary of its findings with regard to the quality of EFAs, including the names of some of the US products which met with its approval.
This is the gold standard in diagnosing and treating food allergies. It is actually a pretty simple process, the problem is the need for absolute consistency - it is easy to slip up without thinking e.g. by feeding table scraps or by giving medications containing food dyes.
Ideally you should also stop using antihistamines and steroids whilst trying this method, but you may need to continue with them for the first couple of weeks of the trial until your cat shows an improvement in his/her condition.
Basically, the idea is that if you feed your cat a limited ingredient diet, ideally with a primary ingredient which your cat has not eaten before, your cat is less likely to be allergic to the food. If s/he is in fact allergic to something in the food, since there are very few ingredients in these foods, you should be able to work out which is the culprit with a little detective work. If s/he is not allergic to the food, the goal is to feed this food, and this food only, to the cat for at least three months. It may take up to four weeks for your cat to improve on such a diet, so feeding it for at least three months gives the cat's body time to heal and to rest the overactive immune system.
After three months, you can gradually try re-introducing ingredients one at a time, and see which (if any) your cat reacts to. It may take up to two weeks to see a reaction to a particular food, so this is a slow process. If your cat reacts to a food, you stop feeding it immediately and know not to feed it in the future. If your cat does not respond to a food, you can include it in his/her diet.
During this trial we fed Harpsie IVD Limited Ingredient Lamb & Pea. He had actually eaten lamb before (it's a relatively common food in the UK) but was not allergic to it. He did so well on his limited ingredient food, and enjoyed it so much, that we did not bother adding any further foods to his diet when the three months were up, so we never worked out which foods were causing his allergies. Beef, dairy and fish are the most common allergens in cats, but I suspect grains were a problem for Harpsie.
You can buy many prescription diets online, but often by the time you have added in shipping costs, you don't end up saving much money. In the end I started buying Harpsie's food from my vet by the case, and they then reduced the price from $2 per can to about $1.40.
Mar Vista Vet has detailed information on elimination diets.
About suggests five foods to consider when implementing an elimination diet.
Hill's sells a hypoallergenic treat for cats in the USA known simply as Hypoallergenic Treats Feline.
Tanya's Feline Chronic Renal Failure Information Centre has details of suppliers of prescription foods in UK, USA and Canada.
Your vet may recommend regular baths to soothe your cat's skin. Cool baths are more soothing than warm ones.
The shampoo page: sorting out the confusion is an article by Dr Roger Ross.
Mar Vista Vet has a lot of information about bathing and shampoos.
Sometimes corticosteroids are prescribed in order to reduce the inflammation that is present. One commonly used steroid is pred (prednisone or prednisolone). Cats metabolise prednisolone better than prednisone (they have to convert prednisone into prednisolone in their bodies anyway before they can use it) so it is usually better to give prednisolone in the first place. Vet Contact reports on a study entitled Bioavailability and activity of prednisone and prednisolone in the feline patient (2004) Graham-Mize CA & Rosser EJ Veterinary Dermatology 15 (s1), pp 10 which supports this view.
Your vet may wish you to start at a higher dose to reduce the inflammation, then reduce to a maintenance dose. If a cat is prescribed steroids, they should not be stopped suddenly, but rather the dose must be tapered. This is because using corticosteroids may suppress the adrenal glands' ability to produce cortisone naturally; so tapering the dose minimises the risk of adrenal insufficiency occurring as a result.
Unfortunately cortico-steroids can have serious side effects with long-term use (including triggering diabetes, fluid retention, hypertension, and masking infections). Corticosteroids cannot normally be used in diabetic cats. If your cat develops congestive heart failure (CHF) within a week of starting corticosteroids, the steroids may be the cause. One study, Corticosteroid-associated congestive heart failure in 12 cats (2004) Smith SA, Tobias AH, Fine DM, Jacob KA, Ployngam T The International Journal of Applied Research in Veterinary Medicine 2 (3) pp159-170 found that some cats developed a unique form of congestive heart failure within seven days of starting steroids. Five of the cats died, but the seven that survived did much better than the typical CHF patient once taken off the steroids.
Newman Veterinary has helpful information about steroids.
Veterinary Partner discusses pred and explains how corticosteroids work.
Mar Vista Vet discusses the potential problems of ongoing steroid use.
Long Beach Animal Hospital has an excellent overview of skin allergies, with photographs of common problems.
Mar Vista Vet has a helpful overview of food allergies and elimination diets.
Mar Vista Vet has information on treating itchy skin.
Skin allergies, atopy, allergic dermatitis, inhalant dermatitis, miliary dermatitis and similar allergic problems in the dog and cat is a helpful overview by Dr Roger Ross.
I am a highly allergic person, so you would think I would have known years earlier that Harpsie had allergies too. However, since the symptoms of allergies in cats are not like those of humans, I had no idea. In humans, allergies tend to manifest themselves as respiratory problems - snuffling, runny eyes and so on. But in cats they tend to manifest themselves as skin and ear problems.
Harpsie had "gunky" ears from a very early age. They were always full of brown stuff. Every time he saw the vet, she would comment on them, and would give us antibiotics or antifungals. These all seemed to work to a degree, some better than others, but as soon as we stopped them, the gunk came back. We simply stocked up on cotton wool buds and I would clean Harpsie's ears several times a week.
Sometimes Harpsie also had itchy skin, and this seemed to get worse as he got older. The itchiness and scabbiness (which we assumed was from him scratching) would leave him with bare patches of skin, usually around or near his neck, but occasionally on his flanks too.
In 1999, when Harpsie was seven, I decided to be firmer with him about wearing his collar when he was in the garden. He had never left the garden, but I didn't want to take any chances. After a couple of weeks of consistent collar-wearing, Harpsie was scratching a lot more around his ears and collar. The vet took a look and said his ears were mucky as usual but there was no sign of an infection or earmites; and to keep an eye on his collar area. Two days later, I checked and the fur was rubbed away in a ring around Harpsie's neck and the skin looked very tender, much worse than two days earlier. Harpsie was rather thin and run down at this time, and we thought he might be stressed by our relatively recent (two months earlier) adoption of two other cats. I had absolutely no idea that the rashes and loss of fur were caused by allergies and by his collar rubbing on already sore skin. I took the collar off that day, but the sore area didn't really settle much thereafter, although at least Harpsie was not scratching as much.
This sort of thing continued for several years. Harpsie would lose his fur on his chin and face and around his neck. He would scratch a lot, and he absolutely loved rubbing his face on the corners of wooden furniture - we were worried he would poke an eye out. We continued to try various medications at intervals but they only helped short term. When we were moving to the USA, we had to postpone Harpsie's rabies shots because his skin was infected on his neck once again, so he needed a course of antibiotics before the rabies shots could be given.
After we moved to the USA, the vets there were none the wiser. Harpsie had the gunk in his ears analysed by the major animal hospital and was put on an antifungal medication, which worked as long as he stayed on it - as soon as he came off it, the gunk returned.
One day when we went to see Harpsie's neurologist, Harpsie had bad skin as usual. The neurologist prescribed antibiotics but also suggested that we should see a dermatologist and recommended one. We had to wait three weeks for the appointment, during which time Harpsie was on antibiotics for 10 days - his neck improved a lot, but he still wasn't right. Finally it was time for our appointment. By this time Harpsie was 13 years old.
dermatologist did lots of tests, and
ascertained that poor Harpsie
was full of infections, despite having been
on antibiotics so recently. He had two types in
one ear (one very severe), one type in the other
ear, one on his chin and one on his back. Also,
the area around his eyes (where he liked to rub on the
sharp edges of furniture) was inflamed. The scary
thing was, you couldn't
see anything at all on his chin or back - she only checked his back
because he suddenly began washing it a lot a week or so
before the appointment. I would never
have guessed these areas were infected.
We are advised to try an elimination diet for three months to see how much it helped. I had no idea how I was going to implement this diet (I free feed my cats) but we had to give it a go.
The dermatologist thought that Harpsie probably had airborne allergies too, but she wanted to see how much treating the food issue would help first, because the treatments she would use for airborne allergies would not interact well with the medications Harpsie took for his many other ailments.
We needed a new cupboard for all the treatments. Harpsie was given more antibiotics, special ear drops (two types), an ear cleaner, cream for his sore eyes and special shampoo - he had to be bathed every other day for the next few weeks. They did suggest shaving him (!) but I had my limits, as did Harpsie. They also recommended Soft Claws to reduce his ability to scratch, but in the end we did not use these. We were told to go back in three weeks for a check up.
Harpsie's elimination diet was to be IVD Lamb & Pea. Since he was allowed to eat nothing else for the next three months, we also had to feed it to the girls. Fortunately they all fell in love with this food immediately, and wolfed it down. And it seemed to help Harpsie very quickly. Here's a message Harpsie wrote to his friends about his next vet visit three weeks later:
"Hi, Harpsie here. Just an update on my latest visit to one of my 'ologists, the dermatologist.
"I'm ashamed to say this visit only cost $285, so clearly I'm losing my touch. It was disgustingly hot getting there (NYC summers are the pits for us longhairs). They left me lying in the scales for ages while they tested my samples. I liked the scales because I could rest my head on the edge. I've gained half a pound in three weeks! - I do love my new food. I got bored on the scales after a while, so I wandered around on the floor.
"The 'ologist came in and kindly agreed to perform the consultation on the floor since that suited me better - I thought that was cool. My skin infection has cleared up, as has one of my ear infections. I am no longer scabby, nor do I scratch all the time. I feel much more comfy! I've even been playing football (well, trying to, the old legs are a lot better but still a bit wobbly). I still have an infection (the second, more severe one) in my ears, and also the one on my chin is still there, so they have to be treated further. But things are looking good overall!
"My new food (IVD Lamb canned) costs US$2 a can! If anybody knows a cheaper source, I think the tinopeners would appreciate the info."
The dermatologist did not stock the food herself, we bought it from one of Harpsie's other 'ologists. We did discover that if we bought an entire case of the food, the cost fell quite a bit, to about US$1.40 per 5 oz can. Even so, when you are feeding a food exclusively to three cats, the cost soon adds up. But it was worth it to see Harpsie feeling so much better. He even rubbed his face less on the wooden furniture.
Because Harpsie was so much recovered, we did not bother pursuing the possibility of airborne allergies. It turned out to be unnecessary: we did finally clear up Harpsie's remaining infections with antibiotics and antifungals; and for the first time in Harpsie's life, they did not return after we stopped the medications. Since he enjoyed it so much, and since it obviously worked for him, Harpsie continued on his elimination diet for the next six months with no problems. We had skin and ear samples tested at intervals, and he remained infection- and itch-free.
In December 2005 Harpsie became slightly quieter, and was less impressed by his prescription diet, having previously wolfed it down. However, the manufacturers had changed the formulation and the girls wouldn't eat it either, so we assumed that was the problem. We tried other formulations (Rabbit & Pea and Duck & Pea) but Harpsie was gradually losing his appetite. In retrospect, I believe this may have been the first early signs of the cancer that was to take his life five months later.
In February 2006, Harpsie had a crisis, and from that time on until the day he died, the only thing he would eat was a non-hypoallergenic diet, Hill's a/d. Strangely enough, Harpsie's skin never erupted though; it was as if his body was so busy coping with the other problems he was experiencing that it did not have time to worry about skin flare-ups. Or maybe his food allergies were finally gone, given the long rest that his immune system had had from the offending foods.
I am so very glad that we finally got Harpsie's food allergies under control in the last year of his life - he was so very much more comfortable as a result, and it gave him a new lease of life. My only regret is that it took us so long to realise what a big problem they were for him. I will always wonder how much the ongoing inflammation of the untreated food allergies and IBD may have contributed to Harpsie's fatal abdominal cancer )-:
This page last updated: 12 February 2008
Links on this page last checked: 2 February 2008
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