Sudden itchy palms may be caused by contact dermatitis, ringworm, insect bite dermatitis and other diseases. 1. contact dermatitis: if the palm of the hand is in contact with allergens, such as detergents, emollients, etc., it can cause contact dermatitis, local inflammatory reaction, resulting in the palm of the hand erythema, papules, pimples, accompanied by itching, resulting in the palm of the palm of the hand to appear suddenly itchy symptoms. 2. Ringworm: If the skin of the palm of the hand is infected with fungi, it can also cause the palm of the hand to appear erythema, papules, papules, desquamation, accompanied by itching, resulting in the palm of the hand to appear suddenly itchy symptoms. 3. Insect bite dermatitis: If mosquitoes bite the palm, the acidic substance secreted by mosquitoes will lead to localized fusiform edematous masses, accompanied by intense itching, resulting in the phenomenon of sudden itching of the palm. It is recommended that patients with sudden itchy palms go to the hospital in a timely manner, after a clear diagnosis of standardized treatment under the guidance of the doctor, so as not to delay the condition.