Hay fever, also called allergic inhalant dermatitis, is really an allergy to plant pollens.  It is especially common in August and September because of the pollens being released from weeds, particularly ragweed.  Unlike humans with hay fever, dogs with pollen allergies itch more than they sneeze.  Itching all over without skin sores or fleas is typical of hay fever in dogs.  Itching and sneezing are the results of nerve irritation by histamine which is released when pollens stimulate the rupture of small histamine containing cells in the skin or mucous membranes.

Incidence 
It is estimated that at least one in 10 dogs have hay fever.   The incidence is even greater in purebred dogs since the risk for hay fever is an inherited trait.  Some of the breeds with higher than average risk for developing hay fever include poodles, Dalmatians, schnauzers, Irish setters, Boston terriers, Scottish terriers, West Highland terriers, cairn terriers, and wire-haired terriers.  

Symptoms/Signs      
The cardinal signs of hay fever in dogs is a generalized itch without...or before...a rash.  The first and most severely affected areas of skin tend to be the face, feet, and "armpits".  Hair loss can develop from the itching being so intense that the dog will bite or scratch off hair shafts.  Thinning hair is seen first around the eyes and on top of the feet.  To a lesser extent there may be itching of the nose, sneezing, and watery eyes.  Signs are usually first noticed in warm weather when the dog is 1 to 3 years of age.  Improvement becomes evident after the first hard frost, which is usually late November in central Missouri.      

Diagnosis 
Skin or blood tests may be used to identify which pollens are the cause for the dog's hay fever.   Your veterinarian will advise you if these tests are necessary for your dog.   

Treatment 
Prescription drugs can be prescribed by your veterinarian that can reduce the sensitivity of the immune system to pollens.  The cortisone family of drugs can safely and economically provide significant relief of symptoms if prescribed in the correct manner.  A new, more expensive, drug called cyclosporine ("Atopica") is an alternative drug to the use of cortisone-like drugs for the treatment of allergies.  It works by a different method than cortisone and has different potential adverse effects.  If skin tests or blood tests are used to identify the specific pollens at fault, a series of many injections with diluted pollens may reduce the severity of hay fever.

Management
Although hay fever cannot be entirely prevented, exposure to pollens and the resulting histamine effects can be reduced by the following:

• Confinement in air conditioned rooms, particularly at night and early morning (air conditioning filters pollens)
• Clipping long hair coats and frequent gentle baths with cool water (reduces pollen entrapment in hair and histamine irritation of nerves causing itching)
• Administering antihistamine such as Benadryl to block histamine effects using dog dosages given to you by your veterinarian

For more information, contact your local veterinarian or the MU Veterinary Medical Teaching Hospital 573-882-7821 or visit www.vmth.missouri.edu

C.B. Chastain, DVM
Professor, University of Missouri
College of Veterinary Medicine