Deep prickly heat occurs mostly in the tropics and is more common in patients with recurrent red cornified rash. The rash occurs on the trunk and neck, and the lesions are dense, non-inflammatory, normal-skinned, deep blisters consistent with sweat pores, about 1-3 mm in diameter, with clear fluid exuding from the blisters when they are punctured. There is no erythema and itching. The disease occurs most often in the tropics and is most common in patients with recurrent red milia. Patients often have compensatory facial sweating and inguinal and axillary lymph node enlargement, most of which appear extensive loss of function of the sweat glands, the enlarged lymph nodes with the disappearance of milia and gradually become smaller. So what are the causes and mechanisms of his pathogenesis? The following is to say a few words. 1, the cause in the hot and humid season, sweating function is not yet sound infants, young children and fat sweaty adults or long-term bedridden patients due to poor sweat excretion, sweat pore obstruction and the onset of the disease. In addition, vitamin A deficiency patients, skin stratum corneum thickening, sweat ducts due to retained sweat and swelling, resulting in sweat pore narrowing or blockage. Pathogenesis There are three steps in the development of prickly heat: the formation of keratin plugs in the ducts of the sweat glands, rupture of the ducts, and extravasation of sweat to the area below the level of obstruction. The level of ductal obstruction determines the type of prickly heat rash. Superficial keratin plugs in the stratum corneum cause prickly heat rash, and the ducts rupture just below the keratin plugs, resulting in the formation of raised, clear blisters, the tops of which are composed entirely of stratum corneum cells. Obstructions deeper in the epidermis cause a red cornual rash, and this type may be erythematous and pruritic, due to the stimulation of skin receptors by enzymes released by sweat damage to epidermal cells. Obstruction of the sweat ducts at the dermal junction of the epidermis ruptures the upper end of the dermal portion of the sweat ducts, which results in sweat retention within the superficial dermis, leading to the formation of a deep rash.