Contact dermatitis occurs whenever a substance touches the skin and causes irritation or inflammation. Irritant contact dermatitis results from touching some type of substance that is inherently irritating to the skin, such as industrial chemicals. Allergic contact dermatitis results from contact with something that would not normally be irritating to the skin, but to which the body initiates an immune response and exhibits an allergic reaction. Both types of contact dermatitis manifest with the same symptoms of a red rash, itchiness, swelling and skin tenderness.
Chemicals
Certain chemicals can sometimes cause irritation of the skin when someone is exposed to them. Compounds in this category include acids and alkaline compounds, chemical solvents and metal salts. Sometimes, the chemicals that affect a particular individual may be hidden in something else, such as chemicals used in clothing manufacture that remain on the clothes, fragrances in cosmetics or the chemicals present in hair dye. Detergents may also cause a reaction. Detergents can be found in many different types of cleaning products and some of these products may contain multiple substances that could set off contact dermatitis. Insecticides also sometimes cause a reaction when they are sprayed in an area and the airborne spray touches the skin of someone sensitive to that chemical.
Plants
Poison ivy, poison oak and poison sumac are well known sources of allergens that affect the skin. These are not the only sources of plant allergens that affect the skin, however. Hidden plant sources that can potentially cause allergic contact dermatitis include mango rinds, cashew nuts and furniture lacquer, explains the American Academy of Dermatology. Some plants may cause a reaction via airborne pollen. Individuals who develop seasonal allergies to ragweed, for example, may also find that they exhibit contact dermatitis if they get ragweed pollen on the skin.
Photosensitive Substances
According to Medline Plus, a website of the National Institutes of Health, some substances only cause contact dermatitis after exposure to light. Types of products that often cause this kind of reaction include some sunscreens, insecticides, perfumes and shaving cream. This type of reaction is called photocontact dermatitis.
Other Substances
Nickel is a common cause of allergic contact dermatitis, according to the American Academy of Dermatology. People who exhibit a reaction to nickel will often notice the problem when wearing jewelry containing nickel. Latex allergies are another common cause of contact dermatitis. Latex can be found in gloves used in medical or laboratory settings as well as in latex condoms. Alternative materials used to make products that normally contain latex are widely available and include nylon and vinyl gloves and polyurethane condoms.
