Why is the skin at the base of the thumb so hard and painful in winter?

The disease of dehiscence.

The occurrence of chapped hands and feet is related to the anatomical and physiological characteristics of the local skin and various external factors, and is also related to the general condition. The anatomical and physiological characteristics of the hands and feet are that the stratum corneum in the palms and heels is extremely thick, with up to more than 100 layers, and the horny cells are irregularly arranged. Moreover, there are no hair follicles and sebaceous glands in these parts, which results in the maintenance of local skin moisture and the moistening of the skin by sebum. Moisture is subject to certain limitations, and when affected by various external factors, skin chapped easily occurs. Therefore, people should apply some moisturizing and moisturizing skin care products on their hands and feet during dry weather seasons, especially in winter, to prevent chapped hands and feet. The influence of external adverse factors is an important cause of chapped skin on hands and feet. For example, when the climate is cold and dry in winter, people are stimulated by the cold wind when working outdoors and lose protection, so the skin becomes dry and rough; or the hands and feet are often rubbed excessively, causing the skin to become dry and thickened, and the elasticity is reduced, resulting in chapped skin. People's excessive exposure to acids, alkalis, organic solvents, etc. in their work or life can cause sebum to decompose, lose its lubricating and protective effect, and cause dry and cracked skin. In addition, patients with tinea manuum and pedis can easily develop chapped skin due to the parasitism and destruction of fungi in the skin, resulting in hyperkeratosis, roughness and lack of sweating. Systemic conditions include physiological skin aging, some hereditary diseases such as ichthyosis, etc., which make the skin dry. When certain external factors act, chapped skin is also prone to occur.