Contact dermatitis

Contact dermatitis is a common problem that is more challenging to diagnose according to cause than to treat. The characteristic redness and scaling found in contact dermatitis can be divided into acute contact dermatitis and chronic contact dermatitis.  It is also considered from the etiologic viewpoint:  primary (irritant) dermatitis and secondary (allergic) dermatitis.

Acute contact dermatitis is usually environmental in origin and easily determined in the acute fulminant form when due to environmental sources- plants such as the rhus plants (poison ivy, oak, and sumac) and the primula and the compositae families) – and industrial/ household sources.  The patient can usually recall the probable cause, when the time from exposure to rash is short, and the cause fresh in the mind.

More challenging is the chronic and often more subtle form of dermatitis, which may the characteristic vesiculobullous / linear and exposed skin predilection for, let’s say, poison ivy.  The frequent association with the workplace and the accompanying compensation/liability issue, as well as with cosmetic exposure, makes essential to determine the cause.

Primary or irritant contact dermatitis is due to an irritant such as soap or bleach, while the secondary or allergic contact dermatitis involves an allergen-antibody reaction.  In the latter, the patient has had repeated exposure to hair dye or the nickel in low karat gold jewelry or silver jewelry.   The diagnosis can be confirmed by using closed patch testing to determine the culprit allergen.  From the cosmetic dermatologic viewpoint, any number of allergens may be found in the cosmetics used, the make-up applied, or even in the shampoo due to a preservative.

The best treatment still remains to eliminate the culprit, where possible.  Topical steroids or calcineurin inhibitors are useful, as is sometimes oral antihistamines.

Larry E. Millikan, MD
New Orleans, LA, USA