Allergy symptoms coming and going; should i take meds only on bad days?

When exposed: Allergy status does not change much, but the amount of allergens (pollen, dust mite, mold spores) in the environment do change. For example, individuals who have symptoms only during pollen season might manage by taking antihistaminics only during these seasons. Defining the allergen sensitivities and when the allergens are highest might require a visit to your doctor.

Depends on frequency: Since it is extremely difficult to predict when you will have exposure to things to which you are allergic, if your symptoms are fairly frequent, i would recommend taking medications daily. If they are somewhat rare, like once a month or once a week, you may take medication only on days you have symptoms and do fairly well. Your doctor or allergist can recommend meds for your situation.