Hives Flashcards
What is urticaria also known as?
Hives/Welts
Describe Hives
Can have flat or raised above the plain of skin
Hives/Welts move and are very itchy and will not involve pus
Describe the difference between hives, psoriasis, eczema, and contact dermatitis
Psoriaisis tends to occur in one spot
Eczema appears reptively on same area
Contact Irritant - WIll be in contact with an irritant and rash will develop where the irritant has contacted
Hives will move and will not have the rawness that is associated with eczema
Movement of hives is classic along with itchiness
Define utricaria
Pruritic plaques with pale, centrally edemateous wheals surrounded by erythematous flare regions
–> Lesions wax and wane over hours to days, are transient, and change size and shape and persist for less than 24 hours
What can help with the differential diagnosis of hives?
Hives will go away unless have chronic utricaria
–> Move and are itchy
Describe the caus of Hives in general? Describe the main presentation of Hives?
Main –> Itchy raised welts that occur after exposure to an allergen and/or host of other non-allergen triggers
–> Allergic reaction is not the case all the time; can have non-allergenic causes as well
Red, warm, and mildly painful to touch
Can be small, round, and ring-shaped or large and randomly shaped
How does Hives present on darker skin?
Harder to diagnose
Describe the etyiology of Hives
Allergic and Non-Allergic to:
1) Foods, drugs
2) URTI’s (especially in children)
3) pressure/Vibration
4) Cold Temprature
5) Stress/Nerves
- Basically anything can cause hives and may never know what the cause was
- Many individuals will be quick to label it as allergic if hives develop - Not the case
- Does not mean you are now allergic to something - often can still take the drug, does not mean you will have anphylaxis (need involvement of a second system)
Describe the pathophysiology of hives
Occurs when a trigger causes high levels of histamine and other chemical messengers to be released by the skin
These substances cause the blood vessels in the affected areas of the skin to open up (often resulting in redness or pinkness) and become leaky
The extra fluid in the tissue causes swelling and itchiness
What can cause the release of histamine leading to hives?
Histamine is released for many reasons including:
1) An allergic reaction - food allergy, insect bite
2) Cold or heat exposure
3) Infection such as a cold
4) certain medications such as NSAIDs or antibiotics
Often no onvious cause can be identified
What is a common cause of hives in children? Issue here?
When a cause for hives can be found, it is most likely a viral infection
Viral URTI’s cause about 40% of hives reactions
Hives reaction resolve as the infection resolves
- Often a drug will get the blame here
Describe Stress Rash
Stress rashes often take the form of hives
- Blotchy areas can be as small as a pencil tip or aas large as a dinner plate
Areas affected by hives will likely be itchy
How long do hives from a viral infection last?
Hives caused by a viral infection are typically acute, and usually last from four to 24 hours
Describe the clinical presentation of Hives
Lesions last 1-24 hours up to several days
–> Their locations can change over this time
Very itchy
Usually benign (but can be part of the naphylaxis/angioedema complex)
Describe the prevalence of Hives
Approx. 20% of the population have had hives
If they stay consistent for a long time in ONE spot, may be something else
Chronic Form –> 1%
- Triggers will rarely be known
- Chronic Idiopathic Utricaria - Itchy long term
Describe Hives and differential diagnosis? Most common cause? When are hives the worst?
If not itchy, Not hives
A very common cause of hives are URT infections (within the last 6 weeks); most common cause in children - Likjely to blame the drug although virus
Typically hives last no more than 24 hours in ONE spot (if longer than 24 hours, start to think of alternate diagnosis)
Hives are worse at night time (because natural cortisol levels are less at night)
Describe an aggressive approach to the treatment of Hives
Dual Therapy (often an oral second gen antihistamine is enough)
1) Second Generation Anti-histamine - Cetirizine
–> H1 receptor antagonists
–> often enough for therapy
2) Zantac - H2 Antagonist
- ACid receptos in the GI system - Aggressive approach
Most evidence suggests that a second gneeration anti-histamine is enough to cover the vast majority of what we need
Describe the relationship between hives and anaphylaxis with medication therapy
Hives are generally called an allergic reaction, but most are not due to that. Most patients have had a cold or virus which more often is the cause 9especially with children)
Easy to blame antibiotics but only 1-3% of penicllin skin reactions are actually an allergy
- The utricaria will last about 1-2 weeks in these cases
- On the next exposure of the antibiotics, most will not progress to something worse (like anaphylaxis)
If the person is truly allergic, they have to be sent home with an Epi-pen
- Sometimes may be done with just a rash, but for sure with any evidence of wheezing, lip swelling
What is the realistic expectation regarding anaphylaxis and hives?
Most hives will not lead to anaphylaxis
- Next exposure leading to anaphylaxis - Can ahppen; however, majority of hives are not going to be allergic in nature
Legal over clinical here - Often listed as an allergy on the patients profile as an allergy
Describe the treatment of hives?
Avoid the trigger (easier said than done)
Second Gneration Anti-histamines
- Drugs of choice for itch
- Try regular dose for a few days
- If no help after 2 weeks, MD may try increasing the dose 2-4X
High speciicity for Hives - Reasonable comfort zone as well
Calamine and cold packs can be useful as well for itch management
Describe the safety of increasing a second genration antihistamine for the treatment of Hives? When is this done? Why?
Hives should not last long; 1-3 days and cause if often gone by then
If no help after 2 weeks, MD may try to increase the dose 2-4x
Can go 4x the dose of anti-histamine with a lot of confidence regarding safety
Confidence that it is hives –> regular doses may sense; however, someone may make the recommendation to go higher
What are some adjunct therapies for hives? Are they effective?
1) 1st Generation Anti-histamines
- Some MD’s add a 1st gen anti-histamine for sedation HS
- No more antihistamine punch or faster acting than a second generation anti-histamine
2) H2 Anatagonists - Leap of faith; Skip it as H1 has the effect in hives
3) Leukotriene Antagonist (Monetlukast/Singulair) PRN - Not recommended for hives
- Hives is a histamine mediated process; allergic rhinitis and asthma leukotrienes are released
- SIngulair not that effective as an agent fro leukotrienes
4) Steroid burts
- Hospital territory and angioedma present
- Massive anti-inflammatory punch
- Can be used for a real bad reaction of hives that is not anaphylaxis to help reduce the inflammatory proces staking place
How can a second generation anti-histamine dose be increased? Example?
Claritin 40 mg (Normal Dose: 10 mg OD)
- Diagnosed by MD
- How we get to 40 mg is irrelevant
1) CAn take all 40 mg at once
2) Can take 10 mg to start, 10 mg later if still there, another 10 mg an hour later if better but still there, and another 10 mg an hour later if almost gone b8ut some itch
3) Can take 20 mg stat, if still around in 3 hours can take another 20 mg
- Depends on the situation but a high does at the start can be done
Is topical therapy for hives reasonable?
Topical therapy can be difficult
- Itchy and movement presnet; so can be hard to predict where the hives will move
