Sudden bumps on the hands can be caused by contact dermatitis, herpes sweat, scabies and other diseases. 1. contact dermatitis: hand contact with irritants or allergens can lead to inflammatory reactions, often occurring in the palm of the hand, fingers and other parts of the performance of erythema, papules, blisters, etc., blisters can be desquamated after drying, and accompanied by severe itching discomfort. 2. Sweat herpes: hand skin allergies, ringworm infection or long-term in a humid environment can cause sweat herpes, can appear in the hands of symmetrical distribution of blisters, usually accompanied by intense itching, tingling and burning sensation and other uncomfortable symptoms. 3. Scabies: an infectious skin disease caused by scabies mites parasitizing the skin. Scabies mites are prone to invade finger cracks, wrists, elbow pockets, armpits and other thin and tender parts of the skin, lesions are mostly symmetrical, manifested as papules, pimples and tunnels. It can also lead to sudden small bumps on the hands and itchy. Surgery suddenly got small bumps should be timely medical consultation, under the guidance of a specialist doctor active treatment, help early relief of uncomfortable symptoms.