Types of Allergies

• Skin allergies are perhaps the most common allergic response, often presenting as hives following an insect bite or as a reaction to a new fly spray or other topical substance.
  
  Allergic respiratory disease or heaves (recurrent airway obstruction) is usually triggered by dust, moldy hay or bedding. Heaves triggered by pollen is most common in southeastern United States.
  
  In the case of heaves, cortisone can reduce the swelling of the airways, a common problem with seasonal (and chronic) respiratory allergies. Skin reactions can be treated with cortisone that is either injected or applied as a topical cream.
  
  

Cortisone Treatment

• Most types of allergies respobnd initially to predisone, a synthetic corticosteroid. Prednisone is quickly converted to the more absorb-able prednisolone by the liver, making it the drug of choice by many veterinarians. Prednisone is usually administered either through injection or as a topical cream.
  
  Corticosteroids are frequently used to treat allergies because of their success in reducing inflammation. But cortisone alone treats only the symptoms, doing nothing toward eliminating the cause.
  
  

Antihistamines Following Cortisone Treatment

• According to Richard A. Mansmann, director of the equine health program at North Carolina State University, antihistamines such as hydroxyzine seem to work fairly well to control seasonal allergies when administered at the beginning of the season, before symptoms appear. If symptoms appear first, your veterinarian may elect to use cortisone to reduce inflammation before beginning an antihistamine regimen.
  
  

Side Effects of Cortisone

• Short-term use is unlikely to produce side effects, but cortisone has the potential to produce serious long-term side effects including laminitis (painful inflammation of the foot in horses that can produce mild to severe symptoms), diabetes and a weakening of the immune system.
  
  Since cortisone suppresses the immune response, horses on long-term use may become more susceptible to bacterial or viral infections
  
  

Cortisone and Pregnancy

• Estrogen also has the ability to increase the effects of corticosteroids so unless the benefits outweigh any potentially harmful effects, cortisone should not be used in horses that are pregnant or lactating. When used in large doses in early pregnancy, malformation of the fetus may occur.