The sudden growth of many small pimples on the hands may be due to eczema, contact dermatitis and systemic diseases such as psoriasis and other factors. 1. Eczema: Eczema is an inflammation of the superficial dermis and epidermis caused by a variety of internal and external factors. Eczema often manifests itself in the form of pimples, papules, and red rashes, which can occur on the head, face, hands, and feet, and is often accompanied by itchy symptoms. 2. Contact dermatitis: contact dermatitis is an acute or chronic inflammatory reaction that occurs at the skin contact site after contact with certain exogenous substances, the most common skin damage is erythematous papules at the contact site. 3. Systemic diseases can also cause different degrees of skin tissue lesions, a class of autoimmune system abnormalities, constantly attacking their own skin tissue, will form a lot of lesions on the skin such as pimples, common diseases such as psoriasis, systemic lupus erythematosus, etc.; the other type of disease for the body metabolite accumulation such as skin amyloidosis, xanthomatosis, etc.. There are many reasons for the sudden growth of small pimples on the hands, others such as flat warts, etc., you need to go to the hospital in a timely manner, to clarify the cause of the disease and then treated.