Dermatitis is a catch-all term for an inflammation of the skin or non-contagious skin rash. Contact dermatitis is usually caused by an allergic reaction or irritation and is usually short term. Eczema refers to a type of atopic dermatitis that tends to be chronic.
Massage may be contraindicated depending on the source and severity of the rash. Massage would not be indicated if the rash is very inflamed or blistered.