Urticaria Flashcards
what is urticaria
Urticaria describes a local or generalised superficial swelling of the skin. The most common cause of urticaria is allergy although non-allergic causes are seen.
What are the features
pale, pink raised skin. Variously described as ‘hives’, ‘wheals’, ‘nettle rash’
pruritic
What is the management
non-sedating antihistamines are first-line
prednisolone is used for severe or resistant episodes
What drugs cause urticaria
aspirin
ACE inhibitors
penicillins
NSAIDs
opiates
What is urticarial eruption
An urticarial eruption is characterized by itchy red wheals (hives) with angio-oedema.
A wheal can last a few minutes and can change form.
What kind of hypersensitivity reaction is urticarial eruption
Urticaria is type 1 IgE-mediated hypersensitivity reaction and so occurs very rapidly after taking the drug.
What is a morbilliform eruption
characterised by a generalised maculopapular rash that is a very common complication of medications.
What type of hypersensitivity reaction is morbilliform eruption
It is a type IV T cell mediated hypersensitivity reaction and so there is a delay of 1-2 weeks between starting the drug and the rash.
However on re-exposure the rash can appear much faster.
Causes of morbilliform eruption
Common causes include:
Amoxicillin - especially if the patient is also infected with EBV (glandular fever)
Beta-lactam antibiotics
Sulphonamides
Allopurinol
What are the causes of fixed drug eruption
Common causes include:
Paracetamol
Sulfonamides
Tetracycline antibiotics
What is fixed drug eruption
A fixed drug eruption is characterised by circular, erythematous patches that may contain a blister that recur in the same location every time the drug is taken.
After healing, pigmentation may remain.
What is lichenoid eruption
Lichenoid eruptions present with purple, pruritic, polygonal, planar papules/plaques.
What is seen in lichenoid eruption and when does it occur
Longitudinal ridging may be seen in the nails but the oral mucosa is not usually affected.
Typically a lichenoid eruption occurs 2 months after starting a medication.
What are the causes of lichenoid eruption
B-blockers
Thiazides
ACE-I
Antimalarials
Gold
Penicillamine
