Hair loss in dogs, also known as alopecia, can be caused by a variety of factors, including allergies, infections, parasites, hormonal imbalances, and immune system disorders. Here are some of the most common causes of hair loss in dogs:

• Allergies: Dogs can have allergic reactions to food, environmental factors, and parasites like fleas and mites. Allergies can cause hair loss when the dog has an allergic reaction to their environment, food, or parasites.

• Infections: Bacterial, yeast, or fungal infections can cause hair loss in dogs. For example, ringworm is a fungal infection that can cause hair loss, and the hair loss pattern is often circular.

• Parasites: Infestations of parasites such as fleas, ticks, and mites can cause hair loss in dogs.

• Hormonal imbalances: Hormonal imbalances can cause hair loss in dogs. For example, hypothyroidism can cause hair loss and thinning.

• Immune system disorders: Autoimmune conditions can cause immune cells to attack hair follicles, causing them to shrink and leading to hair loss.

Treatment for hair loss in dogs depends on the underlying cause. It is important to report hair loss to a veterinarian as soon as possible, as the underlying cause can range from mild to serious in severity.