A dog may begin chewing the hair from the end of its tail because of skin conditions, parasites or behavioral issues. Bringing the dog to the veterinarian can help to determine the root cause of the issue.
Skin irritations are one of the most common causes for a dog biting the end of its tail, as the biting is the only way a dog has to relieve the discomfort. These irritations can be caused by exposure to outside irritants such as pollen or chemicals. For example, taking a dog on a trip to a new outdoor area, such as camping, can expose them to new types of grass and plants that can cause an allergic reaction. Chemical irritations frequently occur when the dog interacts with pesticides or similar plant-related chemicals, or cleaners left unattended in or near the home. These issues can be solved by washing the dog thoroughly and sometimes applying ointment to the tail.
Ticks and fleas are other common causes of tail biting. The dogs chew at the tip and base of the tail in an attempt to scratch away the biting parasites. This is remedied with a flea collar or drops.
Behavioral issues, such as stress at being left alone or moving to a new environment, can also result in a dog biting the end of its tail.