Skin is not smooth, mostly due to external stimulation, keratosis pilaris, may also be caused by other skin diseases. 1. External stimuli: the external environment is cold and dry, if you do not pay attention to skin care, too much water evaporation, resulting in dry skin. Summer heat, often in the external environment, is also the main cause of dry skin. Frequent use of unsuitable cosmetics causes irritation to the skin, resulting in non-smooth skin. 2. Keratosis Pilaris: Keratosis Pilaris is a benign skin disease, which is related to heredity. The main manifestation is the appearance of chicken skin-like pimples on the skin, touching with the hand feels a bit solid, resulting in the skin is not smooth. 3. Other skin diseases: other skin diseases, such as eczema, allergic urticaria, ichthyosis, follicular papules, psoriasis and other diseases, are also the main cause of non-smooth skin. It is recommended to take good care of the skin, if necessary, go to the hospital dermatology department to find out whether it is related to the disease, for the primary disease treatment, do not blindly deal with their own.