Behavior problems are fairly common in dogs and cats, and successfully addressing the issue(s) often requires a bit of time, understanding, and patience. Pet owners often seek out advice and assistance from professionals, including trainers and veterinarians, to help them work through with the issue at hand. Because changes in behavior can have an underlying medical cause, it's important to accurately diagnose the behavior and then consider the possible contributing factors.

Some of the more common changes that owners may notice in a pet's behavior with illness include:

• Changes in a pet's elimination habits
• Changes in sleep patterns
• Hiding behavior
• Changes in their grooming habits
• Changes in vocalization
• Increased anxiety, fear, or panic
• Aggression
• Change in social behavior
• Problems with the pet's gait
• Change in their appetite or thirst

The behavior changes may lead pets to do things that are unacceptable to pet owners and other members of the household including:

• Urinating in undesired locations
• Defecating in undesired locations
• Excessive licking, chewing or scratching
• Excessive barking, whining or crying
• Acts of aggression to other pets or humans
  
  

Each of these behavior changes may have a true behavioral basis for them, or they may be due to an underlying medical problem. Without a complete physical examination, various laboratory tests (blood, urine, and/or fecal) and, possibly, radiographs (x-rays), medical problems cannot be ruled out. Here are some examples of problem behaviors and possible causes (both medical and behavioral diagnoses):
 
House Soiling (Urine and/or Stool)

Medical

• Conditions that can lead to increased drinking and urination - Diabetes mellitus, Cushing's disease, etc.
• Anatomic abnormalities - ectopic ureter, bladder stones, anal gland problems
• Pain - teeth, back pain, or arthritis
• Brain tumors
• Seizures
• Urinary tract infections
• Thyroid disorder (cats)
• Liver disease
• Incontinence
• Food intolerance
• Intestinal parasites
• Gastrointestinal or colon problems
  
  

Behavioral

• Submissive behavior or excitement
• Lack of opportunity to get out of doors or to the litter box (cats)
• Incomplete house training
• Cognitive dysfunction
• Separation anxiety, panic, fear, anxiety
• Litterbox issues (cats)
• Social distress (cats)

Excessive Grooming (licking, scratching, chewing of self)

Medical

• Allergies
• Parasites - intestinal, scabies, house dust mites, demodex mites
• Pain - nerve pain, dental pain, arthritis, or back pain
• Gastrointestinal disease
• Anal gland problems
• Infection - skin infections (bacterial), skin yeast infection, urinary tract infection
• Adverse food reactions or food allergy

Behavioral

• Anxiety, fear, or panic
• Obsessive compulsive disorders
  
  

Aggression

Medical

• Pain
• Thryoid disease
• High blood pressure
• Cancer
• Epilepsy
• Exposure to toxins
• Infectious disease (Rabies, Toxoplasmosis)
• Gastrointestinal disease

Behavioral

• Fear, anxiety, panic
• Territorial
• Resource guarding
• Maternal
• Intercat / interdog issues
• Poor socialization
• Poor handling skills
• Cognitive dysfunction

Excessive Vocalization

Medical

• Hyperthyroidism (cats)
• Brain tumor
• High blood pressure
• Hunger
• Deafness

Behavioral

• Fear, anxiety, or panic
• Aggression
• Cognitive dysfunction
• Boredom
• Alarm or perceived threats
• Species or typical of the breed
• Mating (cats)