Complications of Immunotherapy

Complications of Immunotherapy - Jab Jitters Jive

Immunotherapy (allergen-specific) aims to induce tolerance.

• SCIT (Subcutaneous): Injections.
• SLIT (Sublingual): Under tongue.

Complications:

• Local: At administration site.
  • SCIT: Swelling, redness, pain.
  • SLIT: Oral/pharyngeal itching, mild swelling.
• Systemic: Affect multiple organs.
  • Immediate (minutes to <2 hrs): Urticaria, angioedema, asthma, anaphylaxis.
  • Delayed (>2 hrs to days): Serum sickness-like reactions, worsening eczema.

⭐ SLIT generally has a better safety profile than SCIT regarding severe systemic reactions.

Local Reactions - Skin Deep Issues

• SCIT (Subcutaneous Immunotherapy):
  • Manifestations: Erythema, swelling, induration, pruritus, or pain localized to the injection site.
  • Large Local Reaction (LLR): Defined as swelling >5-10 cm in diameter. Typically peaks at 6-12 hours and resolves within 24-72 hours.
  • Onset: Usually immediate (within 20-30 minutes) but can be delayed (4-8 hours or even up to 24 hours).
• SLIT (Sublingual Immunotherapy):
  • Manifestations: Oral-pharyngeal (itching, lip/tongue swelling), GI symptoms (nausea). Usually mild, transient, occurring shortly after dosing.
• Management:
  • Symptomatic relief: Cold compresses, topical corticosteroids, oral antihistamines.
  • SCIT Dose Adjustment: May be needed for recurrent or large LLRs to improve tolerance.

⭐ Most local reactions to SCIT, though generally mild, manifest within 30 minutes post-injection; however, delayed reactions can occur up to 24 hours later.

Systemic Reactions & Anaphylaxis - Code Red Chaos

• Systemic Reactions (SR): Immune-mediated adverse events beyond local site; spectrum from mild (e.g., urticaria alone) to severe anaphylaxis.
  • Symptoms by System:
    • Cutaneous: Urticaria, angioedema, pruritus, flushing.
    • Respiratory: Dyspnea, wheeze, cough, stridor, hypoxemia, ↓PEF.
    • Cardiovascular: Hypotension, tachycardia, dizziness, syncope, shock.
    • GI: Nausea, vomiting, diarrhea, abdominal cramps.
• Grading: WAO common (Grade 1: mild, skin/subcutaneous; Grade 2-4: moderate-severe multi-organ; Grade 5: fatal).
• Anaphylaxis: Acute, severe, potentially fatal systemic hypersensitivity. Often rapid onset.
  • Diagnosis: NIAID/FAAN clinical criteria (e.g., skin/mucosal + respiratory OR ↓BP).
  • 📌 FIRST & FAST: EPINEPHRINE!
    • Epinephrine: 0.01 mg/kg (max 0.3-0.5 mg) IM 1:1000 (anterolateral thigh). Repeat q5-15min PRN.
    • Position: Supine, legs elevated (unless severe respiratory distress).
    • Oxygen: High flow (maintain SpO2 >94%).
    • IV fluids: Rapid crystalloid bolus for hypotension.
    • Adjuncts: Antihistamines (H1/H2), Corticosteroids (IV/IM), Bronchodilators.
  • Observe for biphasic reaction (4-8 hrs, up to 72 hrs).

⭐ Fatalities from SCIT are rare, estimated at 1 per 2.5 million injections.

Risk Factors & Prevention - Dodging Danger Dots

• Key Risk Factors:
  • Uncontrolled asthma (major predictor).
  • Previous systemic reaction to SCIT.
  • Dosing/administration errors (wrong vial/dose).
  • Concurrent beta-blocker use. 📌 (B-Blockers Bad for Bites!)
  • High degree of skin sensitivity.
  • Peak allergen exposure (e.g., pollen season).
• Prevention Protocol:
  • Patient selection (stable asthma, no contraindications).
  • Dose adjustment: ↓ for large local reactions (>2.5 cm), missed doses, ↑allergen load.
  • Strict vial/dose verification.
  • Observation: Post-SCIT minimum 30 minutes (up to 60 mins for high-risk).
  • Patient education (early symptom reporting).

⭐ Concurrent use of beta-blockers is a significant risk factor for severe/refractory anaphylaxis.

• Rare Complications (Briefly):
  • Serum sickness, Arthus reactions, vasculitis.

High-Yield Points - ⚡ Biggest Takeaways

• Anaphylaxis: most feared systemic reaction; immediate epinephrine is life-saving.
• Local reactions (erythema, swelling) are common, usually self-limiting.
• Systemic reactions vary: mild (urticaria) to severe (laryngeal edema, shock).
• Risk factors: uncontrolled asthma, beta-blockers, high allergen dose, administration errors.
• Delayed reactions like serum sickness are rare.
• Crucial: 30-minute post-injection observation for early detection.
• Emergency kit (epinephrine, antihistamines, corticosteroids) must be available.