CONTACT DERMATITIS   2A

A 30-year-old woman presents to the clinic complaining that she has “an itchy rash all over the place.” She noticed that her legs became red, itchy, and blistered about 2 days after she had been hiking in a heavily wooded area. She says that scratching broke the blisters and afterward the rash became much worse and spread all over. She is convinced that the rash could not be poison ivy because once before she was exposed to that plant and did not develop a rash. On examination, there are erythematous vesicles and bullae in linear streaks on both of her legs. Some areas are weepy, with a yellowish crust. There are ill-defined erythematous plaques studded with papulovesicles on the trunk and arms.

What are the salient features of this patient’s problem? How do you think through her problem?

Salient features: Itchy erythematous rash; history of pre-eruption exposure to the outdoors; previous initial exposure to same antigen; vesicles and bullae

How to think through: This patient’s rash is severe, so it is important to think broadly about other causes besides those linked to the outdoor exposure. No symptoms or signs of systemic illness are mentioned, but a complete review of systems and physical examination (with vital signs) are essential. Could this be atopic dermatitis? (Unlikely—there is no history of atopy or prior similar symptoms) Might this be seborrheic dermatitis? (No, because it typically involves the face and scalp.) A fungal infection? (The pace is too rapid, and the rash is more consistent with dermatitis). Scabies? (No, because of the rapid pace and lack of focus in intertriginous areas.) Could this be impetigo? (Yes; careful examination is warranted to exclude impetigo.) What features of this case provide the strongest evidence for contact dermatitis? (Streaked appearance, a pattern confined to exposed areas of the body, and recent possible exposure to poison ivy with prior contact with this antigen.) What are the two classes of causative agents in contact dermatitis? (Irritants and antigens.) What are other common irritants or antigens?

How should she be treated, topically or systemically? (The weeping and bullae suggest that she may need systemic corticosteroids.) What complications may develop? (Superinfection, especially with Streptococcus spp. and Staphylococcus aureus.)

CONTACT DERMATITIS   2B

What are the essentials of diagnosis and general considerations regarding contact dermatitis?

Essentials of Diagnosis

Erythema and edema, with pruritus, often followed by vesicles and bullae in an area of contact with a suspected agent

A history of previous reaction to suspected contactant

A positive result for a patch test with the agent

May develop secondary infection

General Considerations

An acute or chronic dermatitis that results from direct skin contact with chemicals or allergens

Irritant contact dermatitis is red and scaly, but not vesicular, and is usually caused by irritants such as soaps, detergents, or organic solvents

Allergic contact dermatitis occurs commonly from poison ivy, oak, or sumac; topical medications; hair-care products; preservatives; jewelry (nickel); rubber (latex); vitamin E; essential oils; propolis (from bees); and adhesive tape

Weeping and crusting are typically caused by allergic, rather than irritant, dermatitis

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