Many of us suffer from an itchy rash or dermatitis from time to time. These rashes can be due to having skin conditions such as eczema or seborrhea. However, many itchy rashes occur sporadically and on different parts of the body. One of the most common causes for an itchy rash is due to a condition called contact dermatitis.
What Is Contact Dermatitis?
By definition, contact dermatitis is a rash or dermatitis that occurs after the skin comes in contact with a substance that can cause the rash. Perhaps the best known contact dermatitis is poison oak or poison ivy. However, nearly every substance that we apply to or that comes in contact with the skin can cause a contact dermatitis in a susceptible person. For example, some people will develop a rash when their skin comes in contact with latex or metal that contains nickel. Contact dermatitis differs from irritant dermatitis in that only people that are sensitive to the substance will develop a contact dermatitis, whereas everyone that comes in contact with a skin irritant (such as an acid or drain cleaner) will develop an irritant dermatitis. Therefore, contact dermatitis is a true allergic reaction.
How Do We Develop Contact Dermatitis?
Interestingly, we acquire contact dermatitis allergies throughout life. For a contact dermatitis to develop and occur, we have to be exposed to the contactant, or allergen, at least once before we actually develop a rash to it. Some skin contactants, such as poison ivy, are very allergenic which means that they can cause our skin to produce an allergic reaction or contact dermatitis for the first time after only a few exposures. Other skin contactants may take hundreds of exposures over many years before a contact dermatitis will develop and occur. The more our skin is exposed to a certain substance, the more likely we are to eventually develop a contact dermatitis to it. An example is that health care workers are at a high risk of developing a latex contact allergy due to the exposure of latex gloves on their skin for hours nearly every day. People with chronic skin conditions such as eczema, will develop contact dermatitis more quickly and to more substances than people with intact skin.
The test to definitively diagnose a contact dermatitis is called a patch test. In North America, the patch test has up to 45 common substances that cause contact dermatitis. The American Contact Dermatitis Association decides each year which 45 substances most commonly cause contact dermatitis.
How Is Contact Dermatitis Diagnosed?
There are several clinical clues that a person has a contact dermatitis. One clue is that the dermatitis occurs in specific areas. A rash on the earlobes, around the neck, or on the lower abdomen is a clue that a rash is a contact dermatitis due to nickel as these are areas that nickel in jewelry or belt buckles comes in contact with frequently. Another clue is that the dermatitis can take on the shape of the contactant. For example, a latex allergy may appear as a rash on the hands that stops suddenly at the wrists in the shape and distribution of the latex glove. Once a contact dermatitis is suspected, it can be confirmed or ruled out by a procedure called patch testing. Patch testing can be done by the dermatologist or by most allergists.
What Are The Most Common Contact Dermatitides?
There are several substances that are high on the list for causing contact dermatitis on our skin. Nickel, fragrances, latex and rubber products, hair dye ingredients (paraphenylaminediamine) and adhesives are very common causes of contact dermatitis. Topical medications such as Neosporin and iodine and adhesives such as those found in bandages also commonly cause contact dermatitis. More difficult to diagnose and more rare causes of contact dermatitis include preservatives in topical creams and even topical steroid creams which are often used to treat the contact dermatitis.
How Is Contact Dermatitis Treated?
Once a contact dermatitis has been definitively diagnosed, then avoiding the substance causing the dermatitis is the prescribed treatment. The acute dermatitis can be treated with a topical steroid cream, but will not prevent the contact dermatitis from occurring if the skin comes in contact with the substance again. Currently, there is no known way to induce a tolerance to the contact allergy so that contact to the substance can continue without causing the rash. In fact, continued exposure to the contact allergen will cause a more severe allergic reaction most of the time.
Contact dermatitis is a common skin rash. Contact dermatitis is a true allergic reaction to substances that come in contact with our skin and will only produce a rash in people who have an allergy to the offending substance. Clues to diagnosing a contact dermatitis include the location, shape and distribution of the rash. Definitive diagnosis of contact dermatitis can be made by a procedure called patch testing. Treatment of contact dermatitis is to avoid the substance causing the dermatitis.