- Risk Factors
- Signs & Symptoms
What is contact dermatitis?
Contact dermatitis is a rash that occurs at the site of exposure to a substance capable of producing an allergic reaction or inflaming the skin. It can be caused by noxious, irritating substances or substances to which the patient has developed a skin allergy.
Contact dermatitis is diagnosed by its clinical appearance associated with a compatible history from the patient. Confirmation of allergic contact dermatitis may require a skin challenge with the suspected substance. In addition, other eczematous eruptions must be considered and rejected.
Contact dermatitis generally requires treatment with topical steroid creams, but if extensive, may require taking steroids orally.
What are the causes of contact dermatitis?
There are two forms of contact dermatitis, which have different causes that may include the following:
- Irritant contact dermatitis occurs at the site of the application of a toxic chemical or substance which is directly noxious to the skin.
- The second, allergic contact dermatitis, is an itchy rash that occurs only in people who have developed an allergic sensitivity to that particular chemical or substance.
Such substances are not necessarily irritating or toxic although they may be. They are capable of inducing an immune response in the skin at the site where direct contact occurs. This requires at least one previous contact in the past with that substance to allow the immune system to be primed to react to that substance when it is encountered again.
What are risk factors for contact dermatitis?
Contact dermatitis is caused by the direct application of the inciting substance to unprotected skin. Therefore, the key risk factor is exposure to that substance.
What are symptoms and signs of contact dermatitis?
Contact dermatitis appears as a weepy, oozy, red, elevated rash (an eczematous eruption) at the site of direct contact with the inciting substance.
How is contact dermatitis diagnosed?
Irritant Contact Dermatitis
Irritant contact dermatitis is diagnosed by its clinical appearance associated with appropriate historical clues furnished by the patient during the medical interview. The incubation period between exposure and the onset of symptoms is minutes to hours so that the patient usually is aware of the identity of the causal substance.
Allergic Contact Dermatitis
Allergic contact dermatitis is much more difficult to diagnose. The pattern of the distribution of dermatitis is frequently helpful. For example, allergic contact dermatitis to poison oak, poison ivy, or poison sumac (Toxicodendron plants) typically appears as a linear eruption because the affected skin moves past the leaves of the plant in a line, distributing the allergenic material linearly.
The induction of sensitivity requires at least one previous exposure. However, for mildly allergenic substances, many exposures may be necessary before an allergy is manifest. To correctly identify a particular allergen, it may be necessary to use a challenging technique called "patch testing" to confirm which substance is the cause. This requires at least a 48-hour application of the potential allergen to the skin under an occlusive covering.
The development of eczema at the test site within two to five days after removal of the occlusive material confirms the presence of allergy to that substance. Other eczematous eruptions need to be excluded. This may require culturing for microorganisms, an evaluation of skin scrapings and scale, and perhaps a microscopic examination of a small piece of affected skin removed surgically for biopsy.
What is the best treatment for contact dermatitis?
Acute contact dermatitis is treated topically with evaporative measures. These measures include the application of repeated cycles of cool water compresses followed by drying. Once the weeping and oozing have stopped, then one can apply potent topical steroids two times a day to the affected areas for two to three weeks. Such medications are prescribed by a physician.
If the area of involvement is too extensive to make topical treatment practical, it may be necessary to treat with oral steroids for two to three weeks. It will usually take one to three weeks for the allergen to be entirely removed from the skin so that the rash resolves entirely.
What is the prognosis of contact dermatitis?
If it is possible to avoid contact with the inciting substance, then the prognosis is extremely good. If the cause of contact dermatitis is not discovered and avoided, then it is likely that it will recur upon the next exposure.
In the case of allergic contact dermatitis, there is as yet no reliable technique to "desensitize" the immune system of allergic patients, so avoidance is the only alternative.
Can contact dermatitis be prevented?
Avoidance is the prevention of both allergic contact dermatitis and irritant contact dermatitis. On the other hand, certain precautions can be taken to prevent exposure to either irritants or potent allergens.
- Protective clothing can be quite helpful.
- There are certain so-called "barrier creams" that may be more or less useful in limiting contact with irritants and possible allergens.
- In the case of poison ivy, oak, or sumac, the application of barrier creams is of use before exposure (Stokogard, Hollister Moisture Barrier, and Hydropel are brand names of somewhat effective creams) when available.
Dever, Tara T., Walters, Michelle, and Jacob, Sharon. "Contact Dermatitis in Military Personnel." Dermatitis 22.6 Nov./Dec. 2011: 313-319.
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