Which of the following is listed as a contraindication to diphenhydramine?

• A. Hypertension
• B. Diabetes
• C. Seasonal allergies
• D. Asthma

Answer: (D)

Diphenhydramine is a first‑generation antihistamine with anticholinergic effects that dry secretions. In asthma, drying bronchial secretions can thicken mucus and hinder airway clearance, which can worsen obstruction and patient comfort. It also doesn’t relieve bronchospasm and may contribute to sedation that can depress respiration. For those reasons, asthma is considered a contraindication to using diphenhydramine in the EMS setting. Hypertension and diabetes aren’t contraindications for this medication, and seasonal allergies are actually one of its common indications, since it helps relieve allergic symptoms. In an asthmatic patient with allergic symptoms, focus on bronchodilators and anti-inflammatory treatment rather than diphenhydramine.