Irritant contact dermatitis Flashcards
What symptom is often reported in irritant over contact dermatitis?
Burning
What exam findings differentiate airborne allergic/irritant contact dermatitis vs photoallergic?
Involves the upper eyelids, philtrum, and submental areas.
What are the two categories of contact urticaria?
Immunologic and non-immunologic (see other eczematous reactions slide deck)
What is the most common cause of non-immunologic contact urticaria?
Stinging nettles
What is a key differentiator of irritant contact dermatitis vs allergic contact dermatitis?
There will be widely scattered necrotic epidermal keratinocytes, neutrophil-rich superficial perivascular infiltrate. MILD spongiosis (focal or absent).
What causes worse irritant contact dermatitis, alkalis or acids?
The alkalis are worse! They disrupt barrier lipids and denature proteins. They dissolve keratin and penetrate deeply
What is the pattern of irritant diaper derm?
Spares the skin folds.
Difference between irritant and allergic contact derm?
Irritant is a diagnosis of exclusion –> so if a patch test can’t explain it. You can also get some from the hx of burning
What is more common, irritant or allergic contact dermatitis?
Irritant by a lot (80% vs 20%)
Important to rule out irritant dermatitis clinically
What occupations are most affected by contact dermatitis?
Manufacturing/mining (UK) and agricultural workers (USA)
What are the most common industrial exposures that cause irritant contact dermatitis?
Soap>wet work>petroleum products> cutting oils > coolants
What groups are at the highest risk for contact dermatitis of any type?
Infants, elderly, and those w/ AD because of increased penetration of the chemicals
What is the pathogenesis of irritant contact dermatitis?
Direct damage of keratinocytes by irritant; not immune-mediated and does not require previous sensitization
What are the differences in the mechanisms of the different types of irritant contact dermatitis?
Acute: strong irritants (acids/bases) –>Direct damage to keratinocytes
Chronic (more common): repetitive use of mild irritants (soap/water), over time removes lipid and water-retaining substances of keratinocyte. This leads to increased transepidermal water loss and increased epidermal turnover and inflammation
Frictional irritants: Repeated rubbing, vibrations, and pressure
Cold temperature: low humidity and increased permeability ot irritants
Occlusion/maceration: increased humidity may increase permeability of water-soluble compounds
What are the most common sites of involvement for irritant contact dermatitis?
Hands most common site of involvement, the face is #2
What is the morphology of irritant contact dermatitis?
Depends on the etiology (acute/chronic/frictional/etc)
-Vesicles and necrosis for acute and dryness, scaling, lichenification and fissuring with the more chronic
What types of things can cause pustular/acneiform irritant contact dermatitis?
Metals, croton oil, monaural oils, tars, greases, cutting and metalworking fluids, and naphthalenes
What type of reaction is phytophoto reaction?
It is irritant, phototoxic reaction
fucocoumarins + light (UVA: 320-400nm)
What is the time course of phytophotodermatitis and its dermatopathology?
Fucocoumarins + UVA (320-400nm) –> erythema with or without blistering 24-72 hrs after the contact followed by hyperpigmentation 1-2 weeks later
What is berloque dermatitis?
Pigmentation of the neck/trunk/arms from cologne application containing bergamot oil, which is a furcoumarin (5-methoxypsoralens)
What is the mechanism of fiberglass dermatitis?
Injury via skin penetration –> pruritus/tingling –> papules
What is the treatment for fiberglass dermatitis?
Talcum powder
What is the pathophysiology of alkali-mediated ICD?
Corrosive: dissolve keratin and penetrate deeply (worse than acids)
What are some examples of alkali’s that can cause ICD?
Strong: Ca/Na/K hydroxides; ammonia; lye
Other: Soap, detergent, bleaches, and depilatories
Treatment of alkali mediated ICD?
Apply weak acid (vinegar/lemon juice)
What is the pathophysiology of acid-mediated ICD?
Strong acids = corrosive, weaker acids = astringent (shrinks or constricts tissues)
What is a distinctive feature of sulfuric acid ICD?
Causes severe burns and makes a brownish staining on the skin
Where do people get exposed to sulfuric acid?
Brass and ironworkers, battery makers, jewelers, weapon of vitriol attacks
What is a distinctive feature of nitric acid burns?
Burns w/ yellow discoloration
What things is nitric acid found in?
Fertilizers, explosives
What is unique about hydrofluoric acid ICD?
It penetrates deeply, can affect the bones, nerves, and is incredibly painful
-Sx’s can be delayed up to 24 hrs
What is hydrofluoric acid used for/what industries might people be exposed to it in?
Used for dissolving/etching glass in the semiconductor industry
Treatment for hydrofluoric acid burns?
Calcium gluconate gel, seek emergency care
What skin findings are caused by hydrochloric acid?
Superficial burns –> produces blisters
What cutaneous findings are caused by oxalic acid?
Paresthesia of fingertips; cyanosis; gangrene
What skin findings are cause by phenol?
White eschar
Temporary anesthesia
What systemic problems can phenol cause?
Can be absorbed –> cardiac arrhythmias and glomerulonephritis
How are phenols neutralized on the skin?
65% ethyl EtOH or isopropyl EtOH
