Which type of chemical can cause an allergic reaction in the airways following inhalation?

• A. Oxidizer
• B. Carcinogen
• C. Respiratory Sensitizer
• D. Corrosive

Answer: (C)

When an inhaled chemical triggers an allergic reaction in the airways, it’s because the substance is a respiratory sensitizer. Respiratory sensitizers can cause the immune system to become sensitized in the lungs after exposure. On subsequent inhalations, the immune response is activated, leading to asthma-like symptoms such as wheeze, coughing, and shortness of breath.

The way this happens is that the inhaled chemical (or its metabolite) binds to proteins in the airway lining, forming a hapten-protein complex. Dendritic cells present this complex to T cells, prompting B cells to make specific IgE antibodies. Those IgE antibodies attach to mast cells; when the chemical is inhaled again, it cross-links the IgE on mast cells and triggers release of inflammatory mediators like histamine, causing bronchoconstriction and airway inflammation.

Other types of hazards don’t primarily cause this allergic airway reaction. An oxidizer is hazardous mainly for promoting or supporting combustion and oxidative damage. A carcinogen increases cancer risk rather than provoking an immediate immune-mediated airway allergy. A corrosive causes tissue damage on contact, leading to irritation or burns rather than a specific immune sensitization of the airways.