Page 91 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-6 Rashes

MORPHOLOGY OF ALLERGIC CONTACT DERMATITIS

Eyelid dermatitis
(red eczematous
patches). Potential
allergens include
fragrances,
thimerosal,
neomycin, and
various preser-
ALLERGIC CONTACT DERMATITIS vatives.

Allergic contact dermatitis is one of the rashes most
frequently encountered in the clinician’s office. It is Nickel dermatitis (around the umbilicus)
responsible for a large proportion of occupationally caused by metal snaps
induced skin disease. Urushiol from the sap of poison
ivy, oak, or sumac plants is the most common cause of
allergic contact dermatitis in the United States. The Plaque of dermatitis caused by
clinical morphology, the distribution of the rash, and the repeated use of neomycin-
results from skin patch testing are used to make the containing ointment on a
diagnosis. Patch testing is performed when the caus- Poison ivy–induced superficial cut
ative agent is unknown. Nickel has been the most fre- allergic contact dermatitis,
quent cause of positive patch testing in the world for with the characteristic
years. Urushiol is not tested clinically, because almost linear areas of involvement
100% of the population reacts to this chemical.
Clinical Findings: Allergic contact dermatitis can
manifest in a multitude of ways. The acute form may
show linear streaks of juicy papules and vesicles. Vari-
able amounts of surrounding edema can be seen. Edema
is much more common in the loose skin around the
eyelids and facial region. Chronic allergic contact der-
matitis can manifest with red-pink patches and plaques
with various amounts of lichenification. There are
localized forms and generalized forms. One of the
unique forms of allergic contact dermatitis is the scat-
tered generalized form. Pruritus is an almost universal
finding, and it can be so severe as to cause excoriations
and small ulcerations.
The prototype of allergic contact dermatitis is the
reaction to the poison ivy family of plants. After contact
with this plant, urushiol resin is absorbed into the skin
and initiates the immune system response to cause aller-
gic contact dermatitis. The dose and the duration of
contact with the allergen are important influences on Allergic contact dermatitis
the severity of the rash that develops. Between 3 and 14 of the hands is a frequent
days after exposure, the patient notices linear juicy form of occupationally
papules and vesicles forming at the sites of contact. The induced contact allergy
most commonly affected areas are the extremities. Air-
borne contact dermatitis may be seen from burning of
wood with the poison ivy vine present. These reactions
are usually seen on skin that was not covered with cloth-
ing, and they can be very severe on the face and eyelids,
often causing massive swelling and impeding vision.
The location of the dermatitis can be used as a clue
to the diagnosis. A nurse with hand dermatitis may be
allergic to a component of the gloves being worn occu-
pationally. A young child with a lichenified rash around
the umbilicus may be allergic to a metal component of
a pant snap or zipper. The most common culprit in
these cases is nickel. Finger dermatitis may be caused The diagnosis in all these cases can be made based The presence of only macular erythema needs to be
by the application of acrylic nails or nail polish. Allergic on patch testing. Chambers loaded with specific con- interpreted cautiously but can be considered a positive
contact dermatitis can also be seen within the oral centrations and amounts of known allergens are result in certain situations. Pustular reactions are
cavity, most commonly adjacent to dental amalgams or applied to the back of the individual. The patches considered to be irritant reactions and not relevant.
prostheses. Oral allergic contact dermatitis can mimic are left on for 48 hours and then removed. After an The patient must come back for a final reading 3 to
oral lichen planus. Lichen planus is usually widespread hour, the first reading is made, based on the reaction 7 days after application of the patches. This is the
and affects the mucosa and gingiva both adjacent to and seen under the chamber. Elevation of the skin or most critical reading and gives the most valuable
distant from any dental restorations. vesiculation is considered to be a positive reaction. information.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 77