What is the appropriate physical exam and management approach for a patient presenting with dermatographic urticaria, considering their medical history, age, occupation, and lifestyle?

Physical Examination for Dermatographic Urticaria

The physical examination for dermatographic urticaria centers on performing a dermographism test by firmly stroking the skin with a tongue depressor or blunt object and observing for linear wheal formation within 2-10 minutes. 1

Diagnostic Provocation Testing

The dermographism test is the gold standard for diagnosis and should be performed systematically:

• Apply firm linear pressure to the skin using a tongue depressor, fingernail, or dermographometer across the back or volar forearm 1, 2
• Use sufficient pressure to indent the skin without breaking it—this represents the mechanical stimulus that triggers mast cell degranulation 3, 4
• Observe for the characteristic triple response: initial red line (capillary dilation), followed by axon reflex flare (erythema), and then linear wheal formation within 2-10 minutes 1, 2
• Document the pressure threshold required to elicit whealing, as symptomatic dermographism occurs at lower pressure thresholds than in normal individuals 4
• Note the duration of wheals, which typically resolve within 30-60 minutes in physical urticarias 1, 5

Key Physical Examination Features to Document

Assess the following characteristics during examination:

• Wheal morphology: Linear wheals that precisely follow the pattern of mechanical stroking, distinguishing this from spontaneous urticaria 3, 2
• Pruritus intensity: Symptomatic dermographism is characterized by significant itching with "normal" daily pressures (clothing, scratching), whereas simple dermographism is asymptomatic 4
• Distribution: Test multiple body sites, as the back and extremities are most commonly affected 3
• Associated angioedema: Examine for deeper tissue swelling, though this is uncommon in isolated dermographism 1

Excluding Mimics and Complications

Critical examination elements to rule out alternative diagnoses:

• Wheal duration >24 hours: If individual wheals persist beyond 24 hours, this suggests urticarial vasculitis rather than physical urticaria and requires skin biopsy 6, 5
• Residual changes: True dermographism resolves completely without bruising, hyperpigmentation, or scarring 5
• Systemic symptoms: Assess for fever, arthralgia, or malaise that would indicate systemic disease rather than isolated physical urticaria 6
• Delayed pressure urticaria distinction: Unlike dermographism (immediate onset), delayed pressure urticaria develops 2-6 hours after pressure and can last up to 48 hours 6, 5

Additional Examination Considerations

Evaluate for coexisting conditions and triggers:

• Examine for other physical urticaria triggers by testing cold (ice cube test), heat, or cholinergic stimuli if history suggests multiple physical triggers may coexist 7, 2
• Assess skin for underlying dermatoses, as dermographism can occur in patients with other chronic urticarias 7
• Document occupation and lifestyle factors that may involve repetitive mechanical trauma (tight clothing, manual labor) 2

Common Pitfalls to Avoid

• Insufficient pressure during testing: Using too light a stroke may produce false-negative results; the pressure must be firm enough to indent the skin 4
• Testing too soon after antihistamine use: H1-antihistamines suppress the wheal response and should ideally be discontinued before testing, though this may not be practical in symptomatic patients 1
• Confusing with other physical urticarias: The immediate onset (within minutes) and linear pattern distinguish dermographism from delayed pressure urticaria or cholinergic urticaria 6, 2