Allergic Dermatitis

This can be mild and have features similar to irritant dermatitis. More severe reactions will produce blisters, redness and swelling.

The distribution and configuration of the dermatitis may give clues to the fact that this is allergic. Straight lines, irregular shapes, sharp edges and angular configuration are all clues to aid in diagnosing contact dermatitis.

The history for these patients must include detailed information on activities at work, home, hobbies, medications and clothing.

The location and distribution of the dermatitis can be clue to the causative agent: Eyelids, Face, Scalp, Ears, Neck, Chest, Belt line, Axilla, Vulva, Penis, Thighs, Buttocks, Anal skin, Forearms, Legs.

Patch testing is vital. This is done by applying allergens on a disk and taping them to the back. These will be left on for 48 hours and then removed. One is looking for some redness and swelling in the skin. Reactions are usually read 24-48 hours after removing the patches.

Common allergens will be latex or rubber. It is estimated that between 6-10% of nurses and doctors in hospitals will be allergic to these products. Individuals who have chronic exposure to rubber such as those requiring on-going catheterization also have a high rate of allergic reaction. There is an immediate reaction to latex which can be urticarial and associated with flushing. There may be respiratory symptoms and tachycardia. The more delayed reactions will be those of acute allergic contact dermatitis.

It has been established that allergic reactions to topical steroids are quite common. These can be reactions to either the steroid molecule itself or the vehicle in which it is found. Allergic reactions to one topical steroid may cross-react to others. Clobetasol and Betamethasone are the least likely allergens.

It is difficult to realize allergic reactions to topical corticosteroids as the steroid effect persists, pressing the excessive allergic reaction. It is therefore important to be suspicious of any eruption that one would expect to settle, but does not, with the use of topical steroids. Patch testing is usually done with tixocortol pivolate, Budesonide and hydrocortisone butyrate. These are good screening molecules for other steroids.

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