Hives Flashcards
What is the etiology of hives?
Hives can be caused by almost anything, but they can be categorized into allergic and non-allergic hives.
In children, the most common cause of hives is viral upper respiratory infections like measles.
Are drug-induced hives common?
No, they only make up 5-10% of drug reactions. They should still be on our radar screens.
Antibiotics are the common culprits for drug-induced hives.
Can people get hives from exposure to the cold?
Yes, it is called cold urticaria
What is dermatographism?
It is an immunologic response to response to pressure applied the skin, characterized by local wheal-and-flare erythema followed by edema and itch. It usually takes 5 minutes for hives to appear and they will persist for 15-30 min
What is the clinical presentation of hives?
Lesions last 1-24 hours up to several days (do not stay in the same place, but move around the skin)
Can be very itchy
approx. 20% of population have had it
1% of people suffer from the chronic form (chronic idiopathic urticaria)
Are hives worse during the day?
Hives are worse at night time because natural cortisol (anti-inflammatory) are lower at night
Are drug-induced hives an allergic reaction?
Most cases of drug-induced hives are not allergic (only 1%-3% of penicillin skin reactions are true allergies), but we should still be cautious, especially if wheezing and angioedema are present. If wheezing and angioedema are present, an EpiPen must be given to take care of legal aspects.
How to treat hives?
Avoid the trigger (easier said than done)
2nd generation anti-histamines (drug of choice)
ex. cetirizine
What is the value of using a second agent in addition to a 2nd gen antihistamine in treating hives?
1st gen anti histamines (sedation aspect for sleep)
oral steroid burst (used in more severe cases and brings down inflammation across the entire board)
Are 2nd generation antihistamines always effective in the treatment of chronic hives?
No, they fail to control hives in about 10% of cases. Perhaps other conditions are involved; therefore, other agents are better suited or a new one has to be added to the 2nd generation antihistamine
What are some good anti-itch products that can be used in combination with 2nd gen
Clobetasone (mid-potency steroid)
Calamine
Menthol (as long it is under 1%)
How to differentiate hives from contact dermatitis?
Contact dermatitis and hives both develop itchy rashes, but there are clear differences between the two
Rashes from contact dermatitis can take several days to weeks to heal. Hives on the other hand fade away within minutes to hours
Contact dermatitis also needs skin contact with an irritant or allergen, hives can develop from contact and ingestion of irritant or allergen
Blistering and burning is experienced in contact dermatitis, but not in hives
