What causes cats to shed?
Seasonal shedding is a completely normal and natural physiological phenomenon in cats. Excessive salt intake can burden a cat's kidneys and cause dry fur and hair loss. Malnutrition can also cause cats to have soft and shiny fur. 
Seasonal hair shedding
Cats have a growth cycle and a shedding cycle, and shedding is a completely normal and natural physiological phenomenon. There are two main theories regarding the causes of seasonal shedding: photoperiod and temperature changes.
Photoperiod: Sunlight is crucial for plants and animals. In winter, when the days are shorter, the animal's brain sends a message to the hair follicles: "Hey, it's time to grow hair." In summer, when the days are longer, the brain reduces communication with the hair follicles.
Temperature changes: When spring and summer arrive, cats shed their underfur and grow a fluffy, coarse coat to help them dissipate heat and block out the heat.
When autumn and winter arrive, cats will grow thicker fur to help keep them warm.
Excessive salt intake
Salt is one of the no-nos in cat food. Cats need very little salt, but their sense of taste is poor. If owners aren't careful with their cat's diet, the cat may unknowingly ingest too much salt. Excessive salt not only puts a strain on a cat's kidneys but can also cause dry fur and hair loss.
malnutrition
A cat's fur reflects its quality of life; a well-nourished cat should have a soft, shiny coat. If a cat's fur is dry, dull, brittle, and prone to falling out, it may be malnourished. Generally, cats with weak digestive systems, long-haired cats (such as Persians), and cats with a limited diet are more prone to hair loss due to malnutrition.
Pathological hair loss
Skin diseases and endocrine disorders can also cause cats to lose hair.
Skin diseases: Generally speaking, cats with poor health and low immunity are more prone to skin diseases, so kittens and senior cats need extra attention to skin problems. Once a skin condition is detected, seek veterinary care immediately and isolate the cat for treatment.
Endocrine disorders, such as hyperadrenocorticism. These often occur on the trunk, or appear as spots; the hair is disheveled, and the skin is fragile, thin, and easily torn.
Improper bathing
Improper bathing, such as frequent bathing and the use of human shampoo or inferior shampoo, can damage a cat's hair follicles and cause excessive hair loss.
