What is the management for a 20-week pregnant patient presenting with a pruritic (itchy) and burning rash?

Management of Itchy and Burning Rash in a 20-Week Pregnant Patient

The most critical first step is to determine whether this patient has a rash or pruritus alone, as this fundamentally changes the differential diagnosis and management—if there is a true rash, polymorphic eruption of pregnancy (PEP) is most likely and requires topical corticosteroids and emollients; if pruritus without primary rash, intrahepatic cholestasis of pregnancy (ICP) must be ruled out immediately with serum bile acids due to stillbirth risk. 1, 2

Initial Diagnostic Approach

Key History and Physical Examination Elements

Determine if a primary rash exists or if skin changes are only secondary to scratching:

• True rash present: Look for pruritic urticarial papules and plaques starting in abdominal striae and spreading to proximal thighs, buttocks, and extremities—this is PEP, the most common pregnancy dermatosis 1
• No primary rash (only excoriations): Consider ICP, which presents with generalized pruritus predominantly affecting palms and soles, worse at night, without a primary rash 1

Essential history elements to obtain: 1

• Onset timing and location of symptoms
• Presence of vesicles, bullae, or urticarial plaques
• Distribution pattern (face, trunk, extremities, palms/soles)
• Timing of pruritus (worse at night suggests ICP)
• Personal or family history of atopy
• Medication use (especially opioids, which can cause pruritus)
• Risk factors for hepatitis or liver disease

Mandatory Laboratory Evaluation

If no clear primary rash is present, immediately order: 1, 2

• Serum bile acids (total): Diagnostic threshold >10 μmol/L for ICP
• Liver transaminases (ALT, AST): May be elevated in ICP but not required for diagnosis
• Turnaround time: 4 hours to 14 days depending on assay type available

Management Based on Diagnosis

If Polymorphic Eruption of Pregnancy (PEP) is Diagnosed

PEP is benign to mother and fetus and requires only symptomatic treatment: 3, 4, 5

First-line therapy:

• Emollients regularly, especially after bathing to maintain skin barrier function 3
• Moderate-potency topical corticosteroids (e.g., hydrocortisone) applied to affected areas 3-4 times daily 3, 6
• Loose, breathable clothing made from natural fabrics to reduce friction 3
• Cool compresses and oatmeal baths for symptomatic relief 7

If inadequate response:

• Oral antihistamines (diphenhydramine or hydroxyzine) for pruritus control 5, 7
• Short course of oral prednisolone (not betamethasone or dexamethasone) if severe, as prednisolone is 90% inactivated by placenta 3

Reassurance points:

• No fetal risks associated with PEP 4, 5
• Typically resolves within 6 weeks postpartum 4
• Does not recur in subsequent pregnancies 5

If Intrahepatic Cholestasis of Pregnancy (ICP) is Diagnosed

ICP carries significant fetal risk including stillbirth and requires immediate intervention: 1, 2

Immediate management:

• Start ursodeoxycholic acid (UDCA) 15-20 mg/kg/day divided in 2-3 doses for maternal symptom relief (GRADE 1A recommendation) 2
• UDCA is safe throughout pregnancy and breastfeeding 1

Symptomatic pruritus management: 1

• Emollients to prevent skin dryness
• Avoid hot baths or showers
• Cooling menthol gels for affected areas
• Keep nails shortened
• Cholestyramine or rifampicin (after first trimester) if UDCA insufficient—separate cholestyramine from UDCA by at least 4 hours 1

Delivery timing based on bile acid levels: 1, 2

• Bile acids ≥100 μmol/L: Deliver at 36 0/7 weeks (GRADE 1B)
• Bile acids <100 μmol/L: Deliver between 36 0/7 and 39 0/7 weeks (GRADE 1C)
• Administer antenatal corticosteroids if delivering before 37 0/7 weeks (GRADE 1A)

If Atopic Eruption of Pregnancy (AEP)

Eczematous rash on face, neck, antecubital/popliteal fossae, trunk, and extremities: 1

• Treat similarly to PEP with emollients and moderate-potency topical corticosteroids
• No fetal risks

If Pemphigoid Gestationis (PG) is Suspected

Rare condition with vesicles and bullae—requires immediate dermatology referral: 1

• Associated with fetal risks including prematurity
• Requires immunofluorescence studies for diagnosis
• May require systemic corticosteroids

Critical Pitfalls to Avoid

Do not delay bile acid testing in any pregnant patient with pruritus, even if a rash is present—excoriations from scratching can mimic a primary rash, and missing ICP diagnosis delays critical interventions that prevent stillbirth 1, 2

Never use betamethasone or dexamethasone for pregnancy dermatoses—these cross the placenta readily and can affect the fetus; use prednisolone instead 3

Do not deliver preterm based on clinical suspicion of ICP alone without laboratory confirmation of elevated bile acids (GRADE 1B recommendation) 1, 2

If prescribing cholestyramine for ICP pruritus, monitor PT/INR regularly as it can cause vitamin K deficiency and separate administration from UDCA by at least 4 hours 1, 2

Avoid systemic azole antifungals in first trimester if fungal infection suspected—use topical nystatin instead 3, 8