What is Pain-Related Aggression?

Pain-related aggression in dogs occurs when an animal responds aggressively due to discomfort or pain. This type of aggression is often misunderstood because the signs of pain in dogs can be subtle or misinterpreted as purely behavioral issues.

Recognizing Pain in Dogs

Identifying pain in dogs can be challenging, as they often hide their discomfort. However, there are several signs to watch for:

• Vocalizations:
  • Whimpering or Yelping: A dog may make noises when a painful area is touched or when they move in a way that exacerbates their pain.
  • Growling or Snapping: These can be defensive reactions when a dog anticipates pain, even from a gentle touch.

Behavioral Changes:

Aggression: A previously calm dog may become snappy or show aggression, especially if touched near a sore area.

• Withdrawal: Some dogs may isolate themselves, avoiding interaction with people or other animals.
• Irritability: Dogs in pain may become more irritable, reacting negatively to situations they previously tolerated.

Physical Signs:

• Limping or Favoring a Limb: A noticeable limp or reluctance to use a particular limb can indicate pain in that area.
• Stiffness: Difficulty in getting up, moving slowly, or being hesitant to climb stairs could be signs of joint or muscular pain.
• Reduced Activity: A decrease in playfulness or overall activity level can indicate discomfort.

Changes in Appetite and Grooming:

• Loss of Appetite: Dogs in pain may eat less or refuse food altogether.
• Excessive Licking or Chewing: Constant licking or chewing at a specific spot can be a sign of localized pain or discomfort.

Altered Body Posture:

• Tense or Guarded Stance: A dog may stand or sit in a way that protects the painful area, such as holding their body rigid or curling up more tightly than usual.
• Reluctance to Lie Down or Get Up: Painful dogs may struggle with these movements, showing hesitancy or groaming when they do.

Breathing Changes:

• Panting: While panting can be normal, excessive or unexplained panting might indicate pain, especially if it occurs when the dog is at rest.
• Shallow Breathing: Painful dogs may breathe more shallowly, trying to avoid deep breaths that could exacerbate discomfort, especially in cases of chest or abdominal pain.
• Increased Respiratory Rate: An increased rate of breathing can be a response to pain, even if the dog is not exerting itself.

Facial Expressions:

• Squinting Eyes: A dog in pain might have a more intense, squinted expression.
• Pinned Back Ears: Ears held back tightly against the head can be a sign of discomfort or distress.

The Hormonal Response to Pain

When a dog experiences pain, it triggers a complex hormonal response that can contribute to aggressive behavior. This response is primarily driven by the HPA axis (Hypothalamic-Pituitary-Adrenal axis), which controls the body’s reaction to stress:

• Cortisol Release: Pain stimulates the release of cortisol, a stress hormone. Elevated cortisol levels can make a dog more anxious and reactive, heightening their sensitivity to environmental stimuli and reducing their threshold for aggressive behavior.
• Adrenaline Surge: Alongside cortisol, pain can cause a surge of adrenaline (epinephrine). Adrenaline prepares the body for a “fight or flight” response, increasing heart rate and arousal levels. In a painful situation, this can make a dog more likely to react aggressively to perceived threats.
• Neurotransmitter Imbalance: Pain can alter the balance of neurotransmitters, such as serotonin and dopamine, in the brain. These changes can affect mood and behavior, leading to increased irritability and aggression.

How Pain Influences Aggression

Pain can lower a dog’s tolerance for frustration and fear, making them more prone to aggressive responses. For example, a dog that is normally tolerant of handling may snap or bite if an area that causes pain is touched. Chronic pain, such as arthritis, can lead to a constant state of discomfort, increasing the likelihood of aggression even in situations that would not typically provoke a response.

Key Points

• Neurophysiological Link: A study by Mills et al. highlights the connection between pain and aggression, noting that pain can alter a dog’s neurophysiological state, making them more reactive and less able to cope with stressors.
• Behavioral Manifestations: According to Mills et al., dogs experiencing pain may develop a heightened state of vigilance, which can lead to aggressive behaviors as a defensive mechanism.
• Hormonal Influence: The hormonal changes associated with pain, particularly the release of cortisol and adrenaline, can exacerbate aggression by lowering the dog’s threshold for stress and increasing their reactivity.
• Treatment Approaches: Effective management of pain can reduce aggression. Mills et al. recommend a combination of medical intervention to address pain and behavioral strategies to manage aggression.

Managing Pain-Related Aggression

• Veterinary Assessment: Always consult with a veterinarian to identify any underlying medical conditions that could be causing pain. This may include a thorough physical examination and diagnostic tests.
• Pain Management: Medications, physical therapy, and other treatments may be necessary to manage pain and reduce aggression. This should be done under veterinary supervision.
• Behavioral Support: Work with a qualified canine behaviorist to implement strategies that reduce stress and prevent aggressive episodes. This may include environmental management, training to build positive associations with handling, and gradual desensitization to touch.

Mills DS, Demontigny-Bédard I, Gruen M, Klinck MP, McPeake KJ, Barcelos AM, Hewison L, Van Haevermaet H, Denenberg S, Hauser H, Koch C, Ballantyne K, Wilson C, Mathkari CV, Pounder J, Garcia E, Darder P, Fatjó J, Levine E. Pain and Problem Behavior in Cats and Dogs. Animals (Basel). 2020 Feb 18;10(2):318. doi: 10.3390/ani10020318. PMID: 32085528; PMCID: PMC7071134.