Skin Reactions Flashcards
What is urticaria?
Hives
Describe urticaria?
Lesions appear with 1 hours and last 2-6 hours
Due to mast cell granulation
Type 1 (IgE)> mast cell degranulation> histamine
Dermal oedema
What is the difference between urticaria and eczema?
Urticaria=well defined, smooth surface
Eczema= ill defined, scaly surface
What is angioedema?
Swelling of subcutaneous tissue or mucous membranes
Not itchy
What is anaphylaxis?
Airway, breathing, circulatory problems
What is the diagnostic test for type 1 hypersensitivity reactions?
Skin prick testing
Challenge testing
Serum mast cell tryptase level (anaphylaxis)
Management for type 1 hypersensitivity skin reactions?
Antihistamines (prevent mast cell degranulation)
Corticosteroids (anti inflammatory)
Adrenaline (for anaphylaxis)
What is toxic epidermal necrolysis?
When >30% of skin is effected
Widespread epidermal blistering and sloughing
Drug induced
Keratinocyte death resulting in epidermal detachment at the dermo-epidermal junction
What is maculopapular drug eruption?
o Widespread symmetrical erythematous maculopapular rash
o Onset is 4-21 days after first taking drug
o Normally itchy and mild fever
o Due to Penicillin commonly
What are the indicators that there is a severe reaction of maculopapular drug eruption?
o Mucous membrane involved
o Fever >38.5
o Looks worse [blistering, facial oedema etc
What is erythema nodosum?
o Painful or tender dusky blue-red nodules on shins
o Common in young female adults
o Associated with arthralgia, malaise and fever
What causes erythema nodosum?
STOPTED S = Sarcoidosis P = Pregnancy O = Oral contraceptive T = Tuberculosis T = Throat infections (strep) E = Everything else (IBD, non-hodgekin lymphoma etc.) D = Drugs (sulphonamides eg. co-trimoxazole)
What is the management for erythema nodosum?
Underlying cause + NSAIDs
Resolves spontaneously
What is erythema multiform?
• Type IV hypersensitivity rash of acute onset due to infection or drugs
Hallmark:
– Target lesion
– Dark/dusky central area with surrounding red rings
What causes erythema multiform?
• Herpes simplex virus (most common)
• Mycoplasma pneumoniae (often in children)
Associated with sulphonamide drugs, NSAIDs and phenytoin
What is a fixed drug reaction?
The same area of skin is affected every time
Red, round, painful plaques triggered by tetracycline, NSAIDs, paracetamol
What is acneiform?
Drug induced acne
glucocorticoids
No comedones like normal acne
What eruptions do ACEi cause?
Drug induced bullous pemphigoid (hive-like rash)
What is Stevens-johnson syndrome?
Necrosis of the epidermis
What are photo toxic drug reactions?
When a drug becomes activated by sunlight and causes damage to the skin
Results in increased sensitivity to sunlight (usually UVA)
What drugs commonly cause photo toxic drug reactions?
Doxycycline, Amiodarone, Quinine, Chlorpromazine
What are the sings of phototoxic drug reactions?
o Erythema
o Prickling
o Pigmentation
o Increased skin fragility
What are the investigations for phototoxic drug reactions?
o - Photo-testing
o - Skin biopsy
o - Photo-patch (for type IV)
o - Skin prick (only type I)
What is the management for phototoxic drug reactions?
o - No more drug
o - Topical steroids (heal the skin)
o - Anti-histamines (for itch [type 1])
Most common causative organism of celulitis?
strep. pyrogens
what is impetigo?
Acute bacterial skin infection-usually affects lips “honey crusted lesions”.
Caused by staph aureus
Commonly seen in children
