What are the four routes of allergen exposure?

• A. Injected, Ingested, Absorbed, or Inhaled
• B. Absorbed, Ingested, Injected, Inhaled
• C. Inhaled, Injected, Absorbed, Ingested
• D. Ingested, Inhaled, Injected, Absorbed

Answer: (A)

Allergen exposure can occur through four routes: inhalation, ingestion, injection, and absorption through the skin or mucous membranes. The option that lists injected, ingested, absorbed, or inhaled names each of these routes explicitly, making it the best choice because it covers all the recognized pathways. Think of inhalation as exposure to pollen or dust, ingestion as foods or medicines, injection as venom or vaccines delivered by needle, and absorption as substances entering through the skin or other surfaces. Recognizing these four routes helps explain why reactions vary with different exposures and guides thorough history-taking to identify all potential triggers.