Pediatric emergency medicine trisk 313

allergens in a fashion similar to adults. The distribution, shape, pattern of
the rash, and exposure history, may elucidate the cause ( Table 65.3 ). Some
common contactants include blue dye in diapers and preservatives in wet
wipes, which trigger an itchy diaper rash; toilet seat cleaning supplies
triggering “toilet seat dermatitis ” on the posterior thighs; and the vinyl
lining of certain car seats which can cause “car seat dermatitis ” on the
outer elbows, posterior calves, and occipital scalp. Airborne processes (e.g.,
perfumes, body spray, spray deodorant) can trigger a rash on exposed
surfaces, including eyelids, upper chest, distal arms, and legs. Photoallergic
contact dermatitis occurs when an allergen is applied to the skin and
exposed to the sun. Common agents implicated include phenothiazines,
sulfonamides, thiazides, sunscreen components such as PABA, and some
fragrances.


TABLE 65.3
CAUSES OF CONTACT DERMATITIS


Allergen/irritant

Distribution

Poison ivy, oak, or sumac

Linear plaques with vesicles and crusting
“Black dot poison ivy” (see above)
Lower abdomen (belt buckle, jean snaps);
earlobe (earrings); preauricular and
hands (cellphones)
Around wounds and abrasions

Eyelids
Exposed surfaces including eyelids, face,
upper chest, arms
Widespread under clothing
Widespread under clothing
Groin region in contact with blue dye

Nickel and cobalt

Neomycin
Nail polish (acrylates)
Fragrances (airborne)
Fragrances (in detergents)
Dyes (in clothing)
Disperse blue dye (in
diapers)
Car seat lining (irritant vs.
allergic)
Mango peel
Wet wipes
(methylisothiazolinone)
Cocamidopropyl betaine
(soaps and shampoos)
Lanolin (found in
emollients)
Botanicals (found in many
organic emollients)
Rubber and leather (e.g.,
shoes)
Toilet seats (cleaning

supplies)
Sunscreens, fragrances
(photoallergic contact

Occipital scalp, extensor elbows, posterior
thighs, posterior lower legs
Perioral, hands
Perianal, groin, and perioral
Widespread
Widespread
Widespread
Dorsal feet sparing, especially great toe.
May affect soles
Posterior thighs. May form ring including
lateral and superior buttocks
Photodistributed (face, chest, dorsal hands,
and forearms)


dermatitis)

Irritant Contact Dermatitis
A primary irritant dermatitis is a nonallergic reaction of the skin caused by
a single exposure or repeated contact with an irritating substance. Strong
soaps and detergents, acidic juices, saliva, urine, stool contents, fiberglass
particles, and bubble baths are common causes in children. Lip licker’s
dermatitis occurs as a result of excessive drooling, lip smacking, or lip
licking, typically presenting as a sharply demarcated rash around the mouth.
Juvenile plantar dermatosis is a form of irritant contact dermatitis resulting
from exposure to wetness (e.g., sweat) and occlusive footwear without

socks. This presents with skin fissuring and a glazed appearance of the
plantar surface of the foot. It may be treated with emollients, topical
steroids, and breathable socks. Frictional lichenoid dermatitis is likely
related to repeated rubbing and presents as shiny papules on the elbows,
knees, and back of the hands, and occurs more frequently in individuals
with atopic dermatitis. This condition is usually noted incidentally and is
asymptomatic. Treatment of the above conditions includes minimizing
contact with the primary irritants, frequent application of petroleum-based
barrier ointments, and topical corticosteroids when needed.

Autoeczematization
Autoeczematization, or an Id reaction, occurs in the presence of an allergic
contact dermatitis. The patient later develops a more extensive
monomorphous papular eruption, often accentuated on the extensor aspects
of the elbows and knees as a result of autosensitization. A specialized form
of this process is seen with dermatophyte infection—in particular, tinea
capitis—and is called a dermatophytid. Dermatophytid reactions can be
widespread on the head, neck, and body and are seen most commonly
within the first week after initiating oral antifungal therapy for tinea capitis.
Treatment of Id reactions includes removal or treatment of the inciting
agent (allergen or tinea) and topical steroids for itching.

PHOTOSENSITIVITY
Photosensitivity broadly refers to abnormal or adverse skin reactions to
sunlight. While excessive sun exposure leads to sunburn reactions in most