What is the cause and treatment for sudden lip swelling, possibly due to an allergic reaction from a facial product or dog saliva?

Isolated Lip Swelling: Allergic Angioedema Management

This is isolated allergic angioedema affecting only the upper lip, most likely triggered by either facial product ingredients or dog saliva allergens (Can f 1 or Can f 2), and should be treated with oral antihistamines and allergen avoidance, with close monitoring for any progression to systemic involvement.

Immediate Assessment: Rule Out Anaphylaxis

• The absence of respiratory symptoms, generalized urticaria, gastrointestinal symptoms, or hypotension indicates this is NOT anaphylaxis 1
• Anaphylaxis requires involvement of skin/mucous membranes PLUS at least one additional organ system (respiratory compromise, reduced blood pressure, or persistent GI symptoms) 1
• Since swelling is isolated to the upper lip for 3 days without progression, this represents localized allergic angioedema rather than a systemic hypersensitivity reaction 2

Mechanism and Likely Triggers

This is most likely IgE-mediated (Type I hypersensitivity) allergic angioedema 1, 2:

• Facial products contain multiple potential allergens including fragrances, preservatives, and botanical extracts that can cause contact allergic reactions with subsequent angioedema 1
• Dog saliva contains Can f 1 (18-20 kDa protein) and Can f 2 (22-23 kDa protein), both of which are documented allergens that can trigger IgE-mediated reactions including angioedema 3
• Dog allergens are present in saliva and can cause symptoms within minutes to hours of mucosal contact 1, 3
• The 3-day duration suggests ongoing low-level allergen exposure or delayed resolution rather than acute anaphylaxis 2

Acute Treatment Protocol

First-line treatment is oral H1 antihistamines 4, 2:

• Diphenhydramine 25-50 mg orally every 6 hours, OR
• Cetirizine 10 mg orally once daily, OR
• Loratadine 10 mg orally once daily 4, 2

Add H2 antihistamines for enhanced effect 4:

• Famotidine 20 mg orally twice daily, OR
• Ranitidine 150 mg orally twice daily 4

Consider short course of oral corticosteroids if no improvement in 24-48 hours 4, 2:

• Prednisone 40-60 mg orally daily for 3-5 days 4

Critical Diagnostic Consideration: Bradykinin-Mediated Angioedema

You must rule out non-histaminergic angioedema, which will NOT respond to antihistamines or corticosteroids 4:

• Ask specifically about ACE inhibitor use (lisinopril, enalapril, etc.) - ACE inhibitor-induced angioedema can occur at any time during therapy and requires permanent discontinuation 4
• Ask about family history of recurrent angioedema episodes - hereditary angioedema (HAE) presents with recurrent nonpruritic swelling without urticaria 4
• The presence of isolated lip swelling without urticaria or pruritus raises suspicion for bradykinin-mediated rather than histamine-mediated angioedema 4

If ACE inhibitor-associated or HAE is suspected, standard treatments will fail and specific therapies are required 4:

• C1 inhibitor concentrate 1000-2000 U IV for HAE 4
• Icatibant 30 mg subcutaneously for HAE or ACE inhibitor-induced angioedema 4

Allergen Identification and Avoidance

Immediate allergen avoidance is essential 1, 2:

• Discontinue all facial products used within 48 hours before symptom onset 1
• Prevent dog from licking face or lips - dog saliva contains Can f 1 and Can f 2 allergens that persist on surfaces 1, 3
• Wash face thoroughly with mild soap and water to remove residual allergens 1

Consider allergy testing after acute episode resolves 1, 2:

• Skin prick testing can identify specific allergens from facial products or dog dander/saliva 1
• Specific IgE testing for dog allergens (Can f 1, Can f 2) if dog exposure is suspected 3

Monitoring and Red Flags

Observe closely for progression to systemic involvement 1, 5:

• Development of tongue swelling, throat tightness, difficulty swallowing, or voice changes indicates laryngeal involvement requiring immediate emergency care and epinephrine 4, 5
• Appearance of generalized urticaria, wheezing, shortness of breath, or lightheadedness indicates progression to anaphylaxis requiring epinephrine 0.3 mg IM 4, 5, 6
• Worsening swelling despite antihistamine treatment after 24-48 hours warrants urgent medical evaluation 2

Expected Timeline and Follow-Up

• Allergic angioedema typically improves within 24-72 hours with appropriate antihistamine therapy 2, 6
• If no improvement after 48 hours of antihistamines, consider adding corticosteroids or re-evaluating for non-histaminergic causes 4, 2
• Complete resolution may take up to 5-7 days even with treatment 2

Common Pitfalls to Avoid

• Do not assume all angioedema responds to antihistamines - bradykinin-mediated angioedema (ACE inhibitor-induced or HAE) requires completely different treatment 4
• Do not give epinephrine for isolated lip swelling without systemic symptoms - epinephrine is indicated only for anaphylaxis with multi-system involvement 1, 5
• Do not continue dog licking exposure - repeated allergen exposure will perpetuate symptoms even with medication 1, 3
• Do not ignore lack of response to antihistamines - failure to improve suggests non-IgE-mediated mechanism requiring alternative diagnosis and treatment 4