What can I give my 9 month old for seasonal allergies?

Is it Allergy? Although it's not impossible, it is unusual for infants that age to have seasonal allergies. It usually requires that there would have been prior exposure to the same allergens in the past; even in the most genetically likely children (ie both parents have allergies). Last time the current allergies were out there, your baby wasn't born yet. Make sure that's the reason for the symptoms.
Geographical . Depending where you live, some areas of the country have an inordinate amount of different pollens in a span of 8 weeks. Allergies give you symptoms that wax and wane throughout the day with periods of no symptoms. Colds, specially in day care can give you runny nose for days, well for a week and you start over. Do not overlook an allergy to chemicals or foods.
Not seasonal, yet. Obviously your bady shoud not have seasonal allergies yet, as he/she is only 9-month old and has not experience two of same seasons yet. Allergies require prior exposure. Chidren in daycare have about 60 days of sickness/cold/year, some back-to-back and so may seem long and diagnosed as allergies. If miminal symptoms, do nothing. If severe, consult doc... Good luck...