medical information

Contact dermatitis

Definition

Contact dermatitis is a skin reaction or inflammation of the skin. It is caused by having direct contact with an offending agent or irritant. Contact dermatitis can happen immediately or days after coming in contact with the irritant or trigger.

Description

There are three types of contact dermatitis; irritant contact, allergic contact and photo contact. All types result in itching and swelling of the skin. It can be difficult to distinguish irritant from allergic contact dermatitis, but symptoms for allergic contact dermatitis often are delayed for 1–2 days while irritant contact and photo contact tend to occur immediately. Contact dermatitis may last for up to two to four weeks before it is resolved. Although contact dermatitis itself is not Hand of a 70 year old man affected by contact dermatitis from a rubber glove. (Dr. P. Marazzi, M.D. / Photo Researchers, Inc. Reproduced by permission.) contagious, if the skin becomes damaged from constant itching it could become infected.

In allergic contact dermatitis the immune system overreacts to a causative substance causing hyper-sensitivity. In allergic contact dermatitis the first exposure to the substance does not cause a rash but rather sensitizes the skin so that the second contact causes a reaction. Poison ivy is an example of something that causes allergic contact dermatitis. These allergic reactions can appear at any time during one's life.

In irritant contact dermatitis the causative agents directly damage the skin by removing protective barriers. Some things that cause irritant contact dermatitis include cleaning products, solvents, or detergents. This type often occurs on the hands due because that is the most likely part of the body to be exposed to cleaning. It sometimes takes several exposures to an irritant over time to cause the amount of skin damage that leads to dermatitis.

Photo contact dermatitis occurs when certain substances applied to the skin need to first be activated by sunlight to cause dermatitis. Examples include some perfumes, citrus fruits, sulfa drugs, some sunscreens, coal tar products, and shaving lotion.

If the agent causing the dermatitis is something the person is exposed to at work the term occupational contact dermatitis is used. Examples of this include certain chemicals, fuels, dyes, cleaning agents, solvents or dust.

Demographics

Although anyone can get contact dermatitis, individuals with atopic dermatitis and eczema are at greater risk of developing irritant contact dermatitis. Those living in areas of low humidity and cold temperatures have an increased incidence of contact dermatitis with the exception of cement exposure. Women are at higher risk of contact dermatitis than men and all ages are affected.

Causes and symptoms

Contact dermatitis is always the result of the skin coming in contact with either an irritant or an allergen. A common cause of contact dermatitis are plant allergens including the poisonous plants such as poison ivy and poison oak. Contact dermatitis can be caused by metals such as jewelry, cleaning solutions, detergents, cosmetics, perfumes, chemicals, rubber, and plants. Prescription drugs as well as over the counter drugs can also cause contact dermatitis. Occupational contact dermatitis can be caused by a variety of things including nickel, potassium dichromate and paraphenylenediamine. In elderly patients, the use of topical medication is a frequent cause of contact dermatitis.

It is important to note that although there are some things that tend to cause dermatitis more often than others, anything can cause contact dermatitis and it is different for everyone. It is a misnomer that dermatitis is caused by synthetic compounds and that natural compounds do not cause dermatitis.

Symptoms of contact dermatitis typically include a red rash which may be a raised rash known as hives. The skin will itch and possibly a burning sensation will be felt. Sometimes blisters can occur or dry, red patches that resemble a burn.

Allergic contact dermatitis is an allergic reaction to an allergen. The allergen binds to proteins in the skin sensitizing cells of the immune system. The first exposure to the allergen does not cause a reaction but sensitizes the immune system so that the second time the skin comes in contact with the allergen a reaction occurs. It can take several days after contact for the skin reaction to occur. Because of this it can be difficult to identify the specific allergen. Poison ivy is probably the most common allergen causing contact dermatitis. Repeated exposure to the allergen can cause more severe reactions.

Irritant contact dermatitis is caused by direct damage to the skin by an irritant. Most irritants are chemicals such as acids, alkalis, or solvents but sometimes plants such as hot peppers, garlic and tobacco can cause irritant contact dermatitis. The skin reactions occur within seconds of exposure and are more severe with longer exposure.

Photo dermatitis is caused by sunlight reacting with a substance to transform it into an allergen or irritant. A common cause of photo dermatitis is the oil from citrus fruit. When this is on the skin the sun alters its nature causing dermatitis while without the sun, dermatitis does not occur. This can be caused by other plants including mulberry as well as certain drugs including sulfa drugs, thiazides and tetracycline.

Diagnosis

Diagnosis of contact dermatitis is primarily made by the appearance of the skin. The skin will appear red with swelling. Sometimes fluid-filled vesicles are present. In a chronic condition of contact dermatitis the skin can be scaly and cracked with thickening of the skin. Ruling out cellulitis is important in the diagnosis of contact dermatitis. Cellulitis is associated with pain and sometimes fever, malaise, swollen lymph nodes and a high white blood cell count. Cellulitis can be a very serious condition.

Treatment

Contact dermatitis usually resolves by itself fairly quickly with no treatment. A cold compress can help relieve some of the pain. Calamine lotion and oatmeal baths can relieve some itching. If necessary, an oral antihistamine can be taken to help relieve itching. If more treatment is needed, hydrocortisone cream can be applied in small areas of the skin.

Most cases of contact dermatitis can be treated at home. However, if symptoms make it difficult for the person to sleep, if the skin might be infected, if extreme pain is experienced or the condition does not seem to be getting better after a few days the person should seek medical advice. For more severe cases that require medical care prescription strength corticosteroids in a cream may be recommended or prescription strength antihistamines. At a later date the patient may be referred to an allergist who may do a patch test to help determine the cause of the dermatitis.

Nutrition/Dietetic concerns

None known.

Therapy

None necessary.

Prognosis

Contact dermatitis usually clears up in two to four weeks. The condition worsens with scratching so that should be avoided. Prolonged itching and scratching may lead to neurodermatitis or lichen simplex chronicus. This causes the skin to become thick and leathery in the affected areas. Scratching can also damage the skin and lead to an infection. Once the culprit that caused the dermatitis is identified it should be avoided.

Prevention

The most important thing in contact dermatitis is to identify the cause of the dermatitis and avoid it if possible. If complete avoidance is not possible, protective clothing should be worn to decrease the contact with the trigger, this might include plastic gloves or long pants. If exposure does occur the area of skin affected should be washed as soon as possible with soap and water. Barrier creams can also be applied to protect the skin. If you are not able to identify the causative agent, an allergy specialist may be consulted to do patch testing to determine the causative agent.