Just as people lose their hair over time, so can cats lose their fur as well. However, cats often lose their fur due to allergies such as to flea saliva. This causes cats to over-groom themselves until they literally rip their fur out in spots.
Cats also lick areas that are in pain, so if your cat has a broken bone or bruise, it may lick that area excessively to make it feel better. The end result is a bald spot on your cat.
Any time your cat starts losing hair, it’s a good idea to find the cause. That way you can make sure your cat remains healthy and happy so it can shed more all over your house once more.