The thinning of hair is caused by a variety of conditions. First of all, androgenetic alopecia, also known as seborrheic alopecia and premature baldness, can be seen under the dermatoscope as a reduction in hair density and uneven thickness. The cause is related to polygenic recessive inheritance and androgen overproduction. Other factors include perifollicular inflammation, emotional anxiety and tension, stressful life, and poor living and eating habits, all of which can aggravate the symptoms of androgenetic alopecia, and are mostly treated with oral finasteride or spironolactone and topical minoxidil. Secondly, it is also related to hair malnutrition or metabolic disorders, such as lack of trace elements, essential proteins and severe malnutrition in the body. Certain systemic diseases should also be considered, such as tinea capitis, folliculitis, systemic lupus erythematosus, psoriasis, etc.