He has asthma too. The most effective treatment for allergic rhinitis at any age is a nasal steroid spray. The newer ones, Rhinocort, Flonase and Nasonex appear to have very little systemic absorption and would be acceptable for seasonal use in a child 3 years old. If used year around, it should be under the guidance of a pediatrician or pediatric allergist. Allergy to things encountered in the home, such as house dust mites, cockroaches and animal dander and to outdoor molds is a definite risk factor for developing asthma, particularly in children.
Pollen allergies are more a risk for hay fever.
My wife has been asthmatic for over 30 yrs. I was wondering if some of the new medications will help her. She constantly clears her throat, something that has been going on for over 10 yrs. The treatment of asthma has completely changed over the last 30 years. If your wife's asthma medications have not changed, she should consult a specialist in asthma who can evaluate her treatment program.