Dermatitis Flashcards
What are the two types of contact dermatitis and are they mutually exclusive?
- Allergic contact dermatitis - allergic response caused by contact with a substance
- Irritant contact dermatitis -irritation to the skin by contact with a chemical or physical irritant
Not mutually exclusive -> processes can occur simultaneously in some patients
What type of reaction is an allergic contact dermatitis (ACD) and what are the two phases?
Cell mediated, delayed type IV hypersensitivity reaction
- Sensitization phase - allergen penetrates epidermis, presented by Langerhaans cells to T-cells, takes 1-14 days
- Elicitation phase - re-exposure to allergen activates T-cell response in hours to day
How long can ACD persist after antigen removal? How is it diagnosed?
Up to 3 weeks after removal of agent
Diagnosed via patch testing to identify allergen
What are common allergens which are associated with the Type IV hypersensitivity of ACD?
- Urushiol (poison ivy)
- Nickel jewelry
- Neomycin / bacitracin
- Black hair dye
What does ACD look like acutely and chronically?
Acutely - bright red / erythematous
Chronically - xerotic, fissured, lichenified eczematous plaques
In addition to the common allergens for ACD, what are some common causes which can lead to ACD on the eyelids?
- Cosmetics
- Nickel eyelash curlers
- Antibiotic eyedrops
- Nailpolish removers
- Eyelash adhesives
- Hair dyes
How is ACD treated? How long does it take before skin barrier function has normalized?
- Exposure avoidance
- Topical corticosteroids
- If severe, oral corticosteroids with at LEAST 14 day taper (prevent rebound symptoms)
- Emollients / moisturizers since barrier function takes 4 months to normalize
What is the most common form of contact dermatitis?
Irritant contact dermatitis (ICD). It is also the majority of occupational dermatitis
What causes ICD?
Non-immunologic response to chemical / physical agents, i.e.:
Soap, industrial cleansers, frictional forces
-> risk factors are occupations with repeated exposures to water, soaps, and solvents
How does acute ICD appear? Common locations?
Usually well demarcated (borders of where irritant touched) erythematous and scaly patches and plaques
Severe disease can develop vesicles and bullae
Common locations: Hands, forearms, eyelids, face
How does chronic ICD appear? Who would tend to get it?
Less erythematous, more lichenified than acute ICD. Often fissuring, scaling, and hyperkeratosis
Tends to occur with chronic exposures to solvents -> i.e. housewives
How is ICD managed?
Using more gloves, reducing exposure as much as possible, watching hands in cool / tepid water rather than hot which strips oil out of hands, topical steroids if needed.
What is eczema also called? What other conditions are associated with it?
Atopic dermatitis
Tends to happen in people who have a FHx of:
- Asthma
- Hay fever
- Eczema
Occurs in industrialized urban areas more
What gene is commonly mutated in patients with eczema, and what are they at increased risk for?
Filaggrin, a gene required for proper barrier function of the skin
Increased infection risk due to lack of proper barrier function
-> S. aureus, molluscum, HSV, HPV
What antibody tends to be elevated in atopic dermatitis, and do elimination diets tend to help?
IgE antibodies are high since it is associated with other IgE-related conditions, and eczema is thought to be partially Type 1 hypersensitivty
Dietary modifications do not help