For the red, swollen and itchy hands, it is considered to be due to contact dermatitis, insect bite dermatitis and frostbite. 1. Contact dermatitis: for some patients, it may be due to skin contact with certain substances, such as detergents, disinfectants, chemicals, laundry detergents, etc., which induces localized symptoms of contact dermatitis, which is manifested as red, swollen and itchy hands. 2. Insect bite dermatitis: If the patient stays in the place where there are more mosquitoes for a long time, he may be bitten by mosquitoes, which may cause local metamorphosis, causing insect bite dermatitis, which manifests as redness, swelling, pain and itching symptoms. 3. Frostbite: For example, in winter, the patient may stay in a place with low temperature for a long time, and then appear hand frostbite, because the cold stimulation will cause vasospasm contraction, causing blood flow obstruction, skin or connective tissue inflammatory damage, causing red, swollen, itchy, and painful symptoms of the hand. Patients with red, swollen and itchy hands, do not rule out the existence of other causes, need to go to the regular hospital, with the doctor to improve the examination.