The term "dermatitis" describes an inflammatory response of the skin, caused by contact with allergens or irritants, exposure to sunlight, or by poor circulation, even stress. An example of contact dermatitis is the reaction of a sensitive person's skin to poison ivy, oak or sumac. Contact with these plants, which contain a chemical called urushiol, produces an itchy rash, redness, blisters and scaling. AVOID SCRATCHING. Scratching the rash may spread the inflammation, lead to infection and even leave scars.