Sudden goose bumps may be physiological phenomenon, small spiny moss and so on. 1. Physiological phenomenon: if the skin is suddenly stimulated by cold, the dermal layer of the erector spinae muscle will contract, so that the epithelium of the hair follicles appear similar to chicken skin like goose pimples, this is a normal physiological phenomenon, will disappear automatically. 2. small spiny moss: this is a pathogenesis is not clear, to the hair follicle and like protruding as the characteristics of dermatosis, lesions are mainly in the neck and the outer arm, the main manifestation of the pinhead size follicular papules, dense into pieces. Sudden goose bumps may have other causes, it is recommended to go to the hospital, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.