Hair loss can occur due to various reasons such as environmental factors, hormonal changes, illnesses, and nutrition. Telogen effluvium is a temporary type of hair loss that usually begins a few months after triggers like physical or emotional stress, sudden hormonal changes, or certain illnesses. This condition can typically last up to six months. However, once the triggering factors are removed, hair growth usually resumes spontaneously without the need for treatment, and hair gradually regains its former density.