Dermatitis Flashcards
What are the two main types of contact dermatitis?
irritant
allergic
What usually causes irritant contact dermatitis?
- common non-allergic reaction - due to weak acids or alkalis (e.g. detergents).
What is the cause of allergic contact dermatitis?
- Type IV hypersensitivity reaction.
- often seen on the head following hair dyes.
- Nickel Allergy
Where does irritant contact dermatitis normally present?
Hands
Main feature of irritant contact dermatitis?
Erythema
(crusting and vesicles are rare)
How does an allergic contact dermatitis normally present?
- Acute weeping eczema
Treatment of allergic contact dermatitis?
Topical potent steroids
Give an example of something which can cause both contact and irritant dermatitis?
Cement
- The alkaline may cause an irritant contact dermatitis
- the dichromates cause an allergic reaction
What is dermatitis artfacta?
psycho-dermatological condition characterised by self-inflicted skin lesions
Who normally presents with dermatitis artefacta?
Adolescent females
- strongly associated with personality disorder, dissociative disorders and eating disorders
Features of dermatitis artefacta
- linear/geometric lesions, well-demarcated from normal skin
- skin lesions “appear suddenly” e.g. overnight
- the lesions do not evolve over time
- multiple lesions at various stages of healing
- face (especially cheeks) and the dorsum of the hands most common
Mechanism of injuries in dermatitis artefacta
- scratching with fingernails or other objects
- burning skin with cigarettes
or chemicals (deodorant spray)
Management of dermatitis artefacta
- co-managed by dermatologists, psychologists and psychiatrists
- occlusive dressing
- topical antibiotics (if necessary) - bland emollient
- SSRI and CBT may be helpful
Dermatitis herpetiformis is associated with which other autoimmune disease?
coeliac
What autoimmune phenomenon causes dermatitis herpetiformis?
deposition of IgA in the dermis.
Describe the features of dermatitis herpetiformis
itchy, vesicular skin lesions on the extensor surfaces
(e.g. elbows, knees, buttocks)
What investigation would help diagnose dermatitis herpetiformis?
- skin biopsy
- direct immunofluorescence shows deposition of IgA in a granular pattern in the upper dermis
Management of dermatitis herpetiformis
- gluten-free diet
- dapsone
What is seborrhoeic dermatitis caused by?
- inflammatory reaction to Malassezia furfur
- normal fungal skin inhabitant
Features of seborrhoeic dermatitis
Eczematous lesions on the sebum-rich areas
> scalp (may cause dandruff)
> periorbital, auricular and nasolabial folds
> otitis externa and blepharitis
What conditions are associated with seborrhoeic dermatitis?
Parkinson’s Disease
HIV
Management of Seborrhoeic dermatitis on the scalpe
- OTC containing zinc pyrithione and tar
- 2nd-line agent is ketoconazole
- selenium sulphide and topical corticosteroid
Management of seborrhoeic dermatitis on the body
- topical antifungals: e.g. ketoconazole
- topical steroids: best used for short periods