Dermatitis is a localized inflammation of the skin. In general, inflammation refers to a condition in the body when it is trying to react to a localized injury of tissues. Signs of inflammation include some or all of the following: redness, heat, swelling, pain.
Occupational irritant contact dermatitis is an inflammation caused by substances found in the workplace that come in direct contact with the skin. Signs of irritant contact dermatitis include redness of the skin, blisters, scales or crusts. These symptoms do not necessarily occur at the same time or in all cases. This kind of dermatitis is caused by chemicals that are irritating (e.g., acids, bases, fat-dissolving solvents) to the skin and is localized to the area of contact.
Another kind of contact dermatitis, allergic contact dermatitis, is different because it is an allergic response to skin contact with some allergy-causing material (e.g., poison ivy). Another difference is that allergic dermatitis can occur in other places on the body that did not come in contact with the allergy-causing material.
Source: Canadian Centre for Occupational Health and Safety (CCOHS) www.ccohs.ca