Leader All Day Allergy Cetirizine Hydrochloride Antihistamine Tablets 10 mg 30 ct. An allergy is a sensitivity to a substance that is normally harmless. Flowers trees a family pet or dust are examples of things that can cause an allergy. Even foods like peanut butter fish and milk can cause an allergic reaction in people with sensitivities to them. A substance that triggers an allergy is called an allergen. People can have different reactions to allergens even when they are allergic to the same things. For example an allergen that causes eye inflammation in one person may cause upset stomach in another. Cetirizine hydrochloride tablets 10 mg. Antihistamine. Gluten free. Indoor & outdoor allergies. 24 Hours Relief of: sneezing; runny nose; itchy watery eyes; itchy throat or nose. Compare to Zyrtec active ingredient.