Monday, April 20, 2015

Feline Allergies: Why is my cat grooming so much?

What are allergies, and how do they affect cats?

One of the most common reasons that a cat may seem itchy, twitchy or groom excessively is allergies.  In the allergic state, the cat's immune system "overreacts" to foreign substances (allergens or antigens) to which it is exposed.  Those overreactions are manifested in three ways.  The most common is itching of the skin, either localized (one area) or generalized (all over the cat).  Another manifestation involves the respiratory system and may result in coughing, sneezing, and/or wheezing.  Sometimes, there may be an associated nasal or ocular (eye) discharge.  The third manifestation involves the digestive system, resulting in vomiting or diarrhea.

Severe skin allergies are easy to recognize - some cats develop bare spots on their sides, legs, or abdomen where they lick and chew at their fur. Other cats may develop severe sores or wounds where they cause trauma to themselves. However, it can be hard to recognize the signs of a mild allergy. These cats may twitch their skin or become irritated when petted, or they may lick or chew at the air or nearby objects when they are scratched at the base of the tail. These are itchy cats, even if no one ever observes them grooming excessively.

 If you search "cat licking air" on YouTube, you will find videos of hundreds of itchy cats.

Skin allergies can take a long time to resolve, even when they are not this severe
In some cats, the itchiness eventually becomes so bad that in addition to wounding themselves, the cats develop a secondary bacterial skin infection. This little 2 year old presented to us for a second opinion after 6 months of treatment elsewhere. She was treated with steroids and antibiotics, and after another 5 months, she was doing really well. Now she is maintained on periodic low doses of steroids to prevent this problem from becoming so severe in the future.

Aren't there several types of allergies?

There are four known types of allergies in the cat: contact, flea, food, and inhalant.  Each of these has some common expressions in cats, and each has some unique features.

Contact Allergy
Contact allergies are the least common of the four types of allergies.  They result in a local reaction on the skin. Examples of contact allergy include reactions to flea collars or to types of bedding, such as wool.  If the cat is allergic to those, there will be skin irritation and itching at the points of contact.  Removal of the contact irritant solves the problem.  However, identifying the allergen can require some detective work.

 Flea Allergy
Typical flea allergy scabs on the back of a cat's neck
Flea allergy is common in cats.  A normal cat experiences only minor irritation in response to flea bites, often without any itching.  Many times when we find fleas on a cat, the people he lives with are surprised because the cat has not shown any sign of irritation  or discomfort. The flea allergic cat, on the other hand, has a severe, itch-producing reaction when the flea's saliva is deposited in the skin.  Just one bite causes such intense itching that the cat may severely scratch or chew itself, leading to the removal of large amounts of hair.  There will often be open sores or scabs on the skin, allowing a secondary bacterial infection to begin.  The area most commonly involved is over the rump (just in front of the tail).  In addition, the cat may have numerous, small scabs around the head and neck.  These scabs are called miliary lesions, a term which was coined because the scabs look like millet seeds. These areas are most commonly affected because they are the areas the cat has the most difficulty clearing of fleas.

The most important treatment for flea allergy is to get the cat away from all fleas.  Therefore, strict flea control is the backbone of successful treatment.  Unfortunately, this is not always possible in warm and humid climates, where a new population of fleas can hatch out every 14-21 days.  When strict flea control is not possible, injections of corticosteroids (or "cortisone" or "steroids") can be used to block the allergic reaction and give relief.  This is often a necessary part of dealing with flea allergies.  Fortunately, cats are more resistant to the side-effects of steroids than other species.  If a secondary bacterial infection occurs, appropriate antibiotics must be used.  

Sometimes, one cat in the home may have a severe flea reaction and another will seem completely unaffected. However, it is important to treat ALL animals in the household (dogs, too!) because otherwise, the fleas will continue to reproduce on the untreated pets in the home.

Inhalant Allergy
The most common type of allergy is the inhalant type, or atopy.  Cats may be allergic to all of the same inhaled allergens that affect us.  These include tree pollens (cedar, ash, oak, etc.), grass pollens (especially Bermuda), weed pollens (ragweed, etc.), molds, mildew, and the house dust mite.  Many of these allergies occur seasonally, such as ragweed, cedar, and grass pollens.  However, others are with us all the time, such as molds, mildew, and house dust mites.  When humans inhale these allergens, we express the allergy as a respiratory problem; it is sometimes called "hay fever."  The cat's reaction, however, usually produces severe, generalized itching.  In fact, the most common cause of itching in the cat is inhalant allergy.
Some cats rub their faces, others lick parts of torso or limbs

Most cats that have inhalant allergy react to several allergens.  If the number is small and they are the seasonal type, itching may last for just a few weeks at a time during one or two periods of the year.  If the number of allergens is large or they are they are present year-round, the cat may itch constantly. 

Treatment depends largely on the length of the cat's allergy season.  It involves two approaches.  Steroids will dramatically block the allergic reaction in most cases.  These may be given orally or by injection, depending on the circumstances.  As stated previously, the side effects of steroids are much less common in cats than in people.  If steroids are appropriate for your cat, you will be instructed in their proper use.

A medication called Atopica (cyclosporine) can be used to target and suppress the activity of certain cells (such as eosinophils and mast cells) in the immune system that are involved in inflammation. Inflammation is what causes the irritation and itching sensation due to allergies. Often this medication can be used to help reduce the dose of steroid that is required to treat the allergy, and in some cases, it can control the allergic reaction on its own.

Another useful treatment for allergies is a product called Dermoscent. This topical application is a synergistic blend of 10 essential oils that are rich in essential fatty acids and Vitamin E that has been shown to increase fur shine and decrease dandruff and hair loss. Similarly to Atopica, Dermoscent can help decrease the need for steroid use in allergic cats and can sometimes eventually become the sole treatment for the problem, eliminating the need for oral medications altogether. However, in most cats, steroid and/or cyclosporine treatment may be necessary initially to counter severe inflammation and give the Dermoscent time to work.

Some cats are helped considerably by a hypoallergenic shampoo.  It has been demonstrated that some allergens may be absorbed through the skin.  Frequent bathing is thought to reduce the amount of antigen exposure through this route.  In addition to removing surface antigen, bathing alone will provide some temporary relief from itching and may allow the use of a lower dose of steroids.  Antihistamines are usually of little value in the cat but can be tried. 

Allergy testing can be done intradermally or with a simple blood draw
The second major form of allergy treatment is desensitization with specific antigen injections (or "allergy shots").  Once the specific sources of allergy are identified, very small amounts of the antigen are injected weekly.  This is all in an attempt to reprogram the body's immune system.  It is hoped that as time passes, the immune system will become less reactive to the problem-causing allergens.  If desensitization appears to help the cat, injections will continue for several years.  For most cats, a realistic goal is for the itching to be significantly reduced in severity; in some cats, itching may completely resolve.  Generally, steroids are not used with this treatment protocol.  This therapeutic approach is recommended for the middle-aged or older cat that has year round itching caused by inhalant allergy.  This approach is not successful with food allergy.

Although desensitization is the ideal way to treat inhalant allergy, it does have some drawbacks and may not be the best choice in certain circumstances and for these reasons: 

1.        Cost: This is the most expensive form of treatment. 
2.        Age of Patient: Because many cats develop additional allergies as they get older, young cats may need to be retested 1-3 years later.
3.        Success Rate: About 50% of cats will have an excellent response.  About 25% get partial to good response.  About 25% get little or no response.  The same statistics are true for people undergoing desensitization.
4.        Food Allergies: Although tests for food allergy are available, the reliability of the test is so low that it is not recommended at this time.  A food trial remains the best diagnostic test for food allergy.
5.        Time of Response: The time until apparent response may be 2-5 months, or longer. 
6.        Interference from steroids: Cats must not receive oral steroids for 2 weeks or injectable steroids for 6 weeks prior to testing; these drugs will interfere with the test results.

Food Allergy
Allergic cats are usually affected by proteins sources like chicken and beef
Cats are not likely to be born with food allergies.  More commonly, they develop allergies to food products they have eaten for a long time.  The allergy most frequently develops in response to the protein component of the food; for example, beef, pork, chicken, or turkey.  Food allergy may produce any of the clinical signs previously discussed, including itching, digestive disorders, and respiratory distress.  We recommend testing for food allergy when the clinical signs have been present for several months, when the cat has a poor response to steroids, or when a very young cat itches without other apparent causes of allergy.  Testing is done with a special hypoallergenic diet.  Because it takes at least 8 weeks for all other food products to get out of the system, the cat must eat the special diet exclusively for 8-12 weeks (or more).  If positive response occurs, you will be instructed on how to proceed.  If the diet is not fed exclusively, it will not be a meaningful test.  We cannot overemphasize this.  If any type of table food, treats or vitamins are given, these must be discontinued during the testing period. 

Because cats that are being tested for inhalant allergy generally itch year round, a food allergy dietary test can be performed while the inhalant test and antigen preparation are occurring. 

Whatever the cause of your cat's allergy symptoms, for most cats, therapy of some kind will be required for the rest of their life. For some cats, the treatments may be given seasonally, but for most cats, the treatment must continue year-round, but at the lowest effective dose.

1 comment:

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