Dermatitis Flashcards
What are the most common different types of dermatitis?
- atopic
- seborrhoeic
- varicose
- contact
What term is synonymous with dermatitis?
Eczema
Define contact dermatitis
Contact dermatitis describes dermatitis secondary to external agents, and may be irritant (non-immune mediated) or allergic.
Define irritant dermatitis
Irritant dermatitis is a type of contact dermatitis. It is due to the direct irritant action of a substance on the skin, and is common in for example hospital workers, as a result of frequent hand washing.
Define allergic contact dermatitis
Allergic contact dermatitis is an immune-mediated dermatitis, due to a delayed (type IV) hypersensitivity reaction to a previously encountered antigen
(Irritant dermatitis can happen on first exposure whereas allergic dermatits only happens when there’s enough contact to sensitise the immune system to it!)
What groups of patients are at greater risk of developing a contact allergic dermatitis?
- chronic skin conditions (esp leg ulcers) necessitating prolonged exposure to topical treatments
- occupations
- hairdressers
- building trade
- mechanics
What’s the ratio of allergic to irritant contact dermatitis?
Up to 80% of contact dermatitis is irritant with majority of cases affecting the hands
20% is allergic
What are some of the more common irritants/allergens to be aware of?
- 4% of population allergic to nickel
- 1-3% to cosmetic components
What is the investigation of choice to confirm contact allergic dermatitis?
Patch testing
What does this image show?
A positive reaction on patch testing
What is the management plan for someone found to have an allergen?
The main treatment is avoidance of the allergen
With symptomatic treatment with emollients and steroids of the dermatitis PRN
How can you differentiate between irritant and allergic reaction on patch testing?
Irritant reactions may manifest as erythema, papules or follicular pustules. They tend to be more prominent when the patch is removed, then fade quickly.
Allergic reactions often worsen over the course of patch testing visits.
What is atopic eczema?
An inflammatory skin disease (dermatosis).
In 1 in 5 children.
Starts in early infancy in >80% of cases
What is the diagnostic criteria for atopic dermatitis?
ITCHING plus 3 or >:
- Visible flexural rash (cheeks and extensor surfaces in infants!)
- History of flexural rash (cheeks and extensor surfaces in infants!)
- Personal history of atopy (or first degree relative)
- Dry skin in past year
- Onset before age 2 years
What are the ‘perils of chronic scratching’?
- Lichenification
- Scarring
- Pigmentary changes
- Habit scratching
- Infection
