Allergic contact dermatitis is not a disease. It's a symptom of inflammation that produces red, scaling or itchy skin, as well as blisters.
"The quickest way to develop allergic contact dermatitis is by rubbing something you're allergic to on your bare skin. Something we rub on our skin on a regular basis is soap. Ironically, a product that's supposed to cleanse your skin can end up causing you a lot of pain and aggravation. We'll take a look at five of the most common allergens in soaps that cause dermatitis."
Sodium Laurel Sulfate (SLS) is a detergent that removes too much of oil from our skin, allowing other allergens entry.
Fragrance refers to so many things. Any product that doesn't say it's fragrance-free, likely contains ingredients including common allergens, that are under the uninformative umbrella "Fragrance".
Coconut diethanolamide is also called coconut oil acid, cocamide DEA, ninol, witcamide, and calamide. Like SLS, it removes too much oil and dries skin.
Parabens are used as preservatives. Look for anything with "paraben" or "parahydroxybenzoic" in the name.
Balsam of Peru (myroxylon) is used for its scent and to slow evaporation. It contains the allergen cinnamein, and resins which contain other allergens.
http://health.howstuffworks.com/skin-care/cleansing/tips/5-allergens-in-soaps-cause-dermatitis.htm