The phrase "for cosmetic purposes" means to improve or enhance something in a superficial way, without changing its essential nature. It is often used when referring to procedures or treatments that are intended to make someone look better but do not address any underlying medical issues. For example, using makeup for cosmetic purposes would be to apply it to your face to improve the appearance of your skin, eyes and lips, without necessarily treating any skin conditions such as acne or dark circles under the eyes.