Retinol is not recommended for use during the day, as using it during the day can affect the stability of retinol and may also cause photosensitivity reactions, leading to hyperpigmentation of the patient’s skin and causing the skin to become darker. Therefore, it is generally recommended that patients apply retinol during the night when they are not exposed to light.

Retinol can promote skin metabolism, known as retinol in medicine, which belongs to vitamin A, is an essential substance for maintaining the normal function of epithelial tissues, and has the effect of regulating skin keratinization. If the patient lacks vitamin A in the body, symptoms such as dry skin, perifollicular keratosis, dry eyes, corneal softening, and night blindness may occur. Clinically, it is mainly manifested as the alleviation of perifollicular keratosis, ichthyosis, psoriasis, erythroderma, frostbite, and other diseases. If skin diseases are caused by vitamin A deficiency, retinol can be used for treatment under the guidance of a doctor.