Urticaria - Dermatology

Urticaria

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Urticaria: Basic Facts 

Urticaria 

is a vascular reaction of the skin and appears as 

wheals surrounded by a red halo or flare. 

Cardinal symptom is PRURITUS 

As high as 15-25% 15 25% of the population experience urticaria, urticaria, 

of these 40% have urticaria, urticaria, 

10% have angioedema, angioedema, 

50% 

have both 

Angioedema 

is caused by swelling of subcutaneous tissue 

whereas urticaria 

is caused by swelling of the dermis 

Both angioedema 

and urticaria 

can result in respiratory 

compromise and hypotension 

Angioedema 

and/or urticaria 

may be the cutaneous 

presentation of anaphylaxis, so assessment of the 

respiratory and cardiovascular systems is vital!


Urticaria can evolve over days-weeks days weeks or after a 

number of minutes. 

Individual wheals rarely last >12hrs 

Urticaria can be immunologic (IgE ( IgE dependent, 

type 1 hypersensitivity or complement 

mediated), non-immunologic non immunologic (direct or indirect 

mast cell degranulation), degranulation), 

or idiopathic (more 

than 50% of cases)

Uticaria: Uticaria: 

Basic Facts 

Urticaria can be acute or chronic, chronic urticaria 

lasts 

>6wks 

>50% of chronic urticaria 

is idiopathic. 7-17% 7 17% are caused 

by physical stimuli such as exercise, sun, temperature 

changes, and pressure (the physical urticarias) urticarias 

Physical urticarias 

are confirmed by challenge test with the 

respective trigger. Normally the urticarial 

lesions resolve very 

quickly after the physical stimuli is removed i.e.


Pathophysiology 

(immunologic urticaria): urticaria): 

when an 

antigen binds to IgE 

on the mast cell surface, 

degranulation 

results in release of histamine 

Histamine binds to H1 and H2 receptors to cause 

arteriolar dilatation, venous constriction and 

increased capillary permeability. 

This increases blood flow to the area and 

increased fluid travel to interstitial space


Pathophysiology 

(non-immunologic 

(non immunologic urticaria): urticaria): 

it is not 

dependent on the binding of IgE 

receptors. 

For example, aspirin may induce histamine release 

through a pharmacologic mechanism where its effect on 

arachidonic 

acid metabolism causes a release of 

histamine from mast cells. 

Physical stimuli may induce histamine release through 

direct mast cell degranulation 

Histamine then acts as described previously

Richard E. Klabunde, PhD 


When histamines 

are present: Pc 

decreases due to 

vasodilation, σ 

increases and other 

variables remain 

constant. Thus, 

NDF is more 

negative and more 

fluid leaves the 

capillary bed

Case 1

Case 1: History 

HPI: 36 year old female with a 3 day history of a 

widespread itchy rash. Individual lesions last 

approximately 8hrs. 

PMH: hip replacement 2 months ago 

Allergies: none 

Meds: vicodin, vicodin, 

aspirin (started following hip 

replacement 

FH: no history of eczema or allergies 

SH: lives at home in the city, began using Tide 

detergent 

ROS: negative

Case 1: Exam 

Gen: VSS 

Skin: erythematous papules 

coalescing into plaques (wheals- 

HL) diffusely on the back

Case 1: Question 1 

What other part(s) part(s) 

of the exam are essential? 

a. Respiratory exam 

b. Musculoskeletal exam 

c. Neurologic exam 

d. Psychiatric exam 

e. all of the above


Answer: a 

What other part(s) part(s) 

of the exam are essential? 

a. Respiratory exam 

b. Musculoskeletal exam 

c. Neurologic exam 

d. Psychiatric exam 

e. all of the above

Respiratory Exam 

In cases of acute urticaria 

it is important to make 

sure the patient does not develop airway 

compromise. 

Pulmonary exam would reveal wheezing or signs 

of respiratory distress.


What is the important feature(s) feature(s) 

of the history 

revealed in this case? 

a. She recently began new medications 

b. The lesions last 8hrs 

c. She recently began a new detergent 

d. all of the above 

e. a+b


Answer: e 

What is the important feature(s) feature(s) 

of the history 

revealed in this case? 

a. She recently began new medications 

b. The lesions last 8hrs 

c. She recently began a new detergent 

d. all of the above 

e. a+b

Diagnosis: Aspirin Induced Urticaria 

 

 

Medications are a common cause of urticaria 

and 

angioedema. 

Penicillin and related abx 

are common via the 

immunologic mechanism 

Aspirin is a common cause via the non-immunologic 

non immunologic 

mechanism 

30% of chronic urticaria 

is exacerbated by 

aspirin/NSAIDs 

aspirin/ NSAIDs 

Many patients ask about detergent use, however it 

causes irritant or allergic contact dermatitis NOT 

urticaria

Lesion Duration 

Lesions typically last

Urticarial 

DDx 

vasculitis 

of Urticaria 

Bullous pemphigoid 

Erythema multiforme 

Insect bites 

Allergic contact dermatitis (initial phase) 

The above diagnoses typically have lesions lasting 

>24hrs and thus SHOULD BE BIOPSIED

CASE 2


HPI: While working in the ER, you see a 25 yr old 

woman who was brought in by her husband after being 

found unconscious in the backyard, wheezing and 

developing a rash. 

PMH: asthma 

All: aspirin 

Meds: none 

FH: non-remarkable 

non remarkable 

SH: recently entered cooking school 

ROS: +SOB

Case 2: Exam 

VS: T: 98.6F, HR: 110, 

BP: 90/50, RR: 34 

Gen: women sitting with 

some breathing difficulty 

and in distress 

Respiratory: bilateral 

rhonchi 

Skin: periorbital edema 

and scattered 

erythematous papules 

and plaques on the 

abdomen.


Which of the following is most often implicated 

in anaphylaxis? 

a. Hymenoptera bee sting 

b. Lobster 

c. Peanuts 

d. Penicillin


Answer: d 

Which of the following is most often implicated 

in anaphylaxis? 

a. Hymenoptera sting (2 nd most common cause) 

b. Lobster (less common than others, but 

relatively common among foods) 

c. Peanuts (same as lobster) 

d. Penicillin (most common along with 

NSAIDs 

and radiographic contrast)

Some common causes of anaphylaxis 

 

 

 

 

Foods including peanuts, other nuts, fish, 

shellfish, egg, milk, sesame 

Bee stings 

Latex 

Medications including penicillin, NSAIDs, NSAIDs, 

opiates, IV anesthetics, and radiocontrast 

dyes


What is the next course of action in this patient? 

a. Make a food diary 

b. Administer metoprolol 

c. Assess ABC’s ABC s (airway, breathing, circulation) 

d. Give topical corticosteroids


Answer: c 

What is the next course of action in this patient? 

a. Make a food diary 

b. Administer metoprolol 

(as in asthma a beta 

blocker would be contraindicated) 

c. Assess ABC’s ABC s (airway, breathing, 

circulation) 

d. Give topical corticosteroids

Anaphylaxis 

Anaphylaxis can develop quickly into an 

emergent situation 

Always inquire about oropharyngeal 

swellings or 

breathing difficulty in patients with hives 

If patient gets recurrent swellings without hives 

or pruritus, pruritus, 

consider medications such as ACE 

inhibitors and hereditary angioedema 

as a 

possible cause

Management of Anaphylaxis 

ABC’s ABC s first! 

Make sure airway is patent or else intubation 

may be emergently necessary 

O2 via mask along with 5% metaproterenol 

(beta agonist) for angioedema 

Administer 0.3-0.5ml 0.3 0.5ml in 1:1000 epinephrine 

dilution IM repeating every 10-20min 10 20min as 

necessary

Management of Anaphylaxis 

Second line therapies: 

25-50mg 25 50mg hydroxyzine 

6hrs. 

or benadryl 

IM every 

250mg hydrocortisone or 50mg 

methylprednisolone 

IV every 6hrs for 2-4 2 4 doses 

Aminophylline 

6mg/kg loading over 30min and 

then 0.3-0.9mg/kg/hr 0.3 0.9mg/kg/hr IV 

If patient remains unresponsive, norepinephrine 

and glucagon can be added

CASE 3


HPI: 23 yr old man presents with a 48 hour history of 

widespread rash. He notes that the same lesions are 

present as when his rah began. He does not note any 

new ingestions or illnesses recently and is otherwise 

feeling well 

PMH: none 

All: none 

Meds: none 



SH: lives alone in the city and attends college 

ROS: negative

Case 3: Exam 

Gen: well appearing in 

NAD 

Resp: no wheezes, rales, 

rhonchi 

Skin: pt has scattered well 

circumscribed target 

lesions measuring 5-10mm 

in diameter 

Grouped vesicles are noted 

on the lower lip


What is the most likely diagnosis? 

a. urticaria 

b. erythema 

multiforme 

minor 

c. poison ivy/oak 

d. psoriasis 

e. atopic dermatitis


Answer: b 


a. urticaria 

b. erythema 

(lesions present >24hrs, so unlikely) 

multiforme 

minor 

c. poison ivy/oak (causes contact dermatitis with 

vesicles and it is not targetoid) 

d. psoriasis (see psoriasis module) 

e. atopic dermatitis (see atopic dermatitis module)

Erythema Multiforme 

(EM) 

Erythema multiforme 

minor 

as in this case is 

also know as herpes simplex-associated 

simplex associated 

erythema 

multiforme 

(HAEM) 

Typically, the disease is self-limited self limited and 

recurrent during the spring and fall in young 

adults 

 

Seasonal variation is due to the fact that orolabial 

herpes is triggered by sunlight exposure. Therefore, 

sunlight triggers HSV which triggers EM.

Erythema Multiforme 

on Exam 

The lesions begin as erythematous 

macules 

and 

progress to papules over 1-2 1 2 days 

The central area can become flat or form a 

vesicle 

Typically the areas of involvement are acral, acral, 

and 

involvement of palms and soles is characteristic 

Mucous membrane involvement, especially of 

the oral mucosa can occur (usually involving only 

one mucous membrane)

CASE 4


HPI: 65 yo 

M presents with diffuse rash and blistering 

and crusting of the lips. He has had a cough last week 

and has had a fever for the past 3 days. 

PMH: none 

All: none 

Meds: started on bactrim 

for presumed pneumonia last 

week 



SH: non-remarkable 


ROS: +fever, +fatigue

Case 4: Exam 

Gen: toxic appearing, 

+lymphadenopathy 

Skin: diffuse purpuric 

macules coalescing into 

patches, some with 

central blistering 

localized to chest, arms 

and palms. 

Hemorrhagic crusting of 

the lips



a. erythema 

multiforme 

minor 

b. Stevens-Johnson Stevens Johnson syndrome 

c. disseminated HSV 

d. bullous 

pemphigoid


Answer: b 


a. erythema 

multiforme 

minor (we would have expected 

more acral 

involvement and less mucous membrane 

involvement) 

b. Stevens-Johnson Stevens Johnson syndrome 

c. disseminated 

HSV 

(would expect more grouped 

vesicles on the body) 

d. bullous 

pemphigoid 

(would not expect such an acute, 

severe presentation)

Stevens-Johnson Stevens Johnson Syndrome 

Steven Johnson’s Johnson s Syndrome primarily affects at 

least 2 MM and involves 30% BSA involvement 

10-30% 10 30% BSA involvement is considered 

SJS/TEN overlap


Typically have an accompanying fever and possibly 

prodromal 

URI 

Distribution is more diffuse and lesions are more 

confluent than in erythema 

multiforme 

minor. 

Lesions begin on the face and trunk and often 

appear as purpuric 

macules 

with central blistering 

2+ mucous membranes are involved


In adults, typically caused by medications 

including sulfonamides, antibiotics, NSAIDs, NSAIDs, 

allopurinol, allopurinol, 

and anticonvulsants 

In children, Mycoplasma 

pneumoniae 

is also a 

common cause 

Radiation therapy of malignancy may also trigger 

SJS

Complications 

Most common complication of EM/SJS is 

VISUAL LOSS due to corneal scarring from the 

MM involvement 

TEN is associated with significant mortality (5- (5 

15%) 

 

Factors associated with worse outcome are age, how 

long offending medication is continued, HIV status, 

and BSA of involvement

Treatment in EM Minor 

EM minor is often self-limited self limited in children 

and resolves within 2-6 2 6 weeks 

In herpes associated cases, antivirals 

can be 

used as prophylactically 

and will prevent 

recurrence in 50% of cases

Treatment in SJS 

In SJS, secondary infection is a possibility given skin 

loss and therefore antibiotics should be given 

In cases of >10-30% >10 30% skin involvement, the patient 

should be placed in a burn unit and IVIg 

is 

considered 

In severe cases, biopsy is ALWAYS done to 

confirm the diagnosis and it is the only 

dermatologic condition where a frozen section is 

done

END OF MODULE

Urticaria - Dermatology

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