While fireworks may physically hurt your dog's ears if an explosive device gets too near the ear canal or close enough to singe the hair, the more likely and common type of harm fireworks cause is the emotional unhinging of the dog's sense of well-being.
According to Louise Thompson, an accredited animal behavior consultant, firework explosions cause dogs to panic because explosions are short-lived events that dogs don't understand and to which they can't get fully accustomed. Thus, dogs often react negatively, particularly if they don't get used to loud noise exposure.
Thompson says fireworks can emit sounds of up to 190 decibels, which is 110 to 115 decibels higher than the 75-to-80-decibel upper range of human hearing. These loud, quick bursts are commonly distressing to many dogs; they can cause irreversible ear damage including tinnitus or loss of hearing. It's best to keep your dog at home in as quiet a place as possible while fireworks are in use. Playing some music to mask the gunpowder claps can be soothing.
Emotional & Psychological Harm
Perhaps more disturbing and damaging for your dog is his emotional or psychological response to loud noise, which is another reason to keep him at home. Many dogs become confused and anxious by sudden loud noises and will bolt or make efforts otherwise to get away. Some even break out of confined areas. Many canines end up in shelters where they may or may not be recovered. Fearful dogs can get hit by cars and may be injured or killed, not to mention hurt themselves trying to scratch or bite their way out of confinement.