Contact dermatitus, eczema and allergies are a few common causes of rashes on hands and fingers, according to the American Osteopathic College of Dermatology. The majority of hand rashes are called contact dermatitus because they are caused by contact with substances in the environment.
Contact dermatitis is skin inflammation caused by an adverse reaction to something it touches, such as chemicals in detergent, soap or a fragrance, according to Healthgrades. Other forms of contact include exposure to plants such as poison oak or ivy. Eczema can be treated with skin moisturizers. Allergies to food and medications are potentially serious sources of rash.