Allergies & Atopy 3

Antihistamines

Antihistamines are widely used in both the human and animal medical fields. Most of the antihistamines used in veterinary medicine are antihistamines that were designed for and used primarily by humans. Antihistamines have been shown to be effective in controlling allergies in up to 30% of dogs and 70% of cats. When used as part of a treatment plan including fatty acids and avoidance, the percent of respondents goes much higher.

Every animal will respond differently to each of the different antihistamines. Therefore, several different antihistamines may have to be used before an effective one is found. Every antihistamine has a different dose and risk of side effects. Antihistamines should be used with veterinary guidance. Some common side effects include sedation, hyperactivity, constipation, dry mouth, and inappetence. The correct antihistamine given at the proper dose should not cause unwanted side effects. For severely itchy dogs, mild sedation may be a positive and desired side effect.

Antihistamines come in several forms including H1 and H2 blockers. While the H2 blockers (Claritin, Seldane, and Hismanal) have been shown to be very effective in treating human allergies, they have not been shown to be effective in treating canine or feline allergies, and are therefore, not recommended for pet use. There are many different H1 antihistamines available on the market, but veterinary use is usually restricted to the following.

AntihistamineTrade NamePossible Side Effects
DiphenhydramineBenadryl SedationDry mouth
HydroxyzineAtaraxSedation, no dosage for cats
ClemastinefumarateTavistSedation, dry mouth
ChlorpheniramineChlor-TrimetonLethargy, diarrh

Immunotherapy (Hyposensitization)

Immunotherapy has been described as the mainstay of treatment for canine atopy. It is indicated in animals where the avoidance of antigens is impossible, symptoms are present for more than 4 to 6 months out of the year, and fatty acids and antihistamines do not provide satisfactory results.

An animal must undergo intradermal skin testing prior to hyposensitization. After the antigens to which the animal is allergic have been identified through testing, a commercially prepared injection containing the altered antigens is injected into the dog. Depending on the type of product used, a series of weekly or monthly shots are given. The animal then becomes de-sensitized to the offending allergens. Success is as high as 80% with this treatment plan. Treatment is time consuming and requires a dedicated owner and veterinarian. I feel that this treatment is an excellent option in severe cases of atopy, especially in young dogs. This testing and treatment option is currently grossly underutilized in the veterinary profession, but is gaining in popularity. If you have an allergic pet that is not responding to conventional treatment, seriously consider this as a treatment option.

Steroids

Almost everyone out there has an opinion on steroids and many of them are bad; that is, unless they were suffering from severe itching, coughing, or pain and had to take steroids for relief, in which case, they may sing their praises. Steroids are extremely effective for relieving severe itching and inflammation. The problem is that they can have many short and long-term side effects, if not used correctly.

Steroids are usually administered in one of two forms, injectable and in tablet form. The steroids being discussed here are corticosteroids and are not the anabolic steroids used by body builders. Anabolic steroids are a completely different drug and have no application in treating animal allergies. There are many different forms of corticosteroids currently available on the market. They vary widely in their duration of activity and strength.I have seen steroids grossly abused when used as a cure-all without proper diagnosis of a condition or using other alternative treatments. At the same time, I have also seen veterinarians and owners refuse to use them to alleviate severe itching and pain when they were clearly the best choice and should have been used. Steroids are a drug, and just like any other drug, they can be misused. If used correctly, they can be as safe as any other drug that we use. The problem is that they work so well that they are often overused. Because of their potential side effects, they should be used very carefully, and at the lowest effective dose. They are usually reserved as one of the last lines of treatments, but if nothing else works, use the steroids.

Steroids have a wide range of activity and affect several different systems within the body. They are closely involved with the skin, immune, and endocrine system. The effects on the immune and endocrine system can create the widespread and multisystem side effects seen with their use.

Injectable: Injectable forms of steroids include betamethasone, dexamethasone, flumethasone, methylprednisolone, and triamcinolone. These agents are usually given intramuscularly and have between one week and six months duration depending on the product, the dose, and the individual animal.

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