Hives (urticaria) Flashcards
what it urticarcia
- hives
- can affect patients at any age, has lifetime prevalence around 20%
- can be acute (lasting 6 weeks) or chronic (more than 6 weeks)
- typically benign and self limiting but can be a symptom of life threatening anaphylaxis or rareyl indicate significant underlying disease
Pathophysiology of hives
- histamine and toher mediators are released from mast cells and basophils
- if the release occurs in the dermis is causes hives, if occurs in deeper dermis and subcutaneous tissue results in agioedema
- IgE often mediates release of histamine but non-IgE mediators also exist
what are the 3 main potential causes of hives
- IgE mediated: contact or food allergens, insect venom, medication
Non-IgE mediated: autoimmune idease, infections, lymphoma, vasculitis
Non-immunologically mediated: elevation of core body temp, light, physical stimuli, medication
clinical presentation of hives
- red or skin coloured wheals that are raised and well-circumscribed, often with centeral pallow
- can be less than a cm to several
- can be round, oval ro wave
- can coalesce as they inlarge
- often intensely pruitic, some cases burn or sting
- symptoms can last from minutes -> months or yeats but generally last less than 24 hours
red flag signs and symptoms
Angioedema is present
They are experiencing stridor, wheezing, or other indicators of respiratory distress
There are signs or symptoms of a systemic illness
The lesions are hyperpigmented, bruised, blistered, or ulcered, or
The lesions have persisted for more than 48 hours
general management for hives
non pharm
- want ot identify and remove cause of skin reaction, prodive symptomatic relief until spontaneous resolution occurs
- mainstay of treatment is avoiding the trigger
- can wear loose fititng lcohtes, cool baths/ apply cool compress, gentle fragrance free soaps and detergents
- keep nails short to prevent fingernail traume with scratching
common drugs that can worsen hives
Alcohol and medications like acetylsalicylic acid and NSAIDs should be avoided, as these may worsen symptoms.
when to treat hives with pharm measures
ndicated when trigger avoidance is not possible
when no trigger can be identified
symptom relief is needed despite trigger avoidance.
first line treatment for acute hives
H1-antihistamines have been shown to reduce wheal formation, pruritus, and disruption of sleep and other daily activities
- use second gen (cetirizine and desloratadine) as first line because longer acting and relatively non sedating
- can consider first gen at bedtime in younger healthy patients to help with seep
*avoid frist gen in older patients due to anticholinergic side effects
increasing dose of second generation antihistamines
in some cases they are titrated to two to four times their normal dose to control symptoms
- increases risk of adverse effects, not recommneded in context of self treatment
topical antihistamines for treatment of hives
not recommended due to risk of contact dermatitis
what to do when hives are not sufficiently controlled with second generation anti histamines
- add ranitidine (H2 antihistamine, ntoe tohers are H1)
- generally not required due to limited data to support
when to add corticosteroids for hives
severe cases like angioedema or if symptoms persist mroe than a few days
- short course of oral corticosteroid (prednisone or prednisolone)
- > patient referral required (RPh cannot prescribe for this)
when to suggest carrying around epipen
cases where systemic symptoms are suggested and identified a trigger assocaited with more severe reaction (insect stings, certain foods)
- carry epinephrine autoinjector to treat anaphylaxis if it were to occur
first line treatment for chornic hives
second generation H1-antihistamines at standard dose
- dose these agents daily rather than prn
*. Some evidence suggests that cetirizine may be modestly more effective than other agents in treating chronic hives.
what is the step up if 2nd gen antihistmaines are not sufficient to control chronic hives
- if fail to provide sufficient control of sympoms within 2-4 weeks (or sooner if symptoms are intolerable) dose can be titrated up to 4x usual dose
- increases risk of adverse effects like sedation, not recommneded in contect of self care
what is the step up if increased dose 2nd gen antihistmaines are not sufficient to control chronic hives?
What after that?
- add on omalizumab
- if thats still inadequate in 6 monnths, add cyclosporine to second gen H1 antihistamine therapy instead
*Therapy with omalizumab or cyclosporine should be under the supervision of a specialist.
alternative treatment options if none of mainstay step ups for chonic hives work
- consider H2-antihistamine, but these receptos are not involved in itch
- leukotriene receptor antagonist (e.g., montelukast) could be prescribed and may be particularly useful in patients with an NSAID intolerance or cold urticaria.
*RPh cant prescribe that
- finally doxepin (tricyclic antidepreaant) could be prescribed
*others are Dapsone, phototherapy or IV immunoglobulins -> but no studies directly comparing these interventions
corticosteroids in treatment of chronic hives
- potent topical corticosteroids can use when symptoms are severe (flare up)
- may be beneficial for localized delayed pressure urticaria
-
monitoring and follow up for hives
- patients or caregivers monitor daily
- RPh in 7 days
- if no imporvement or worsening, refer
- in case of chornic hives, spontaneous remission can occur at any time, evaluate every 3-6 months
