A: Seasonal allergies mean just what they say; they come and go with the seasons. The most common spring and summer allergy triggers are to tree pollen, which crops up in April and May; to grass in May to July; and to ragweed from August to September. Remember, though, that these are just general guidelines, and the timing of your child's allergies can vary depending on where you live. Perennial allergies are year-round, indoor allergies to things like dust, mold, cockroaches, feathers, and pet dander. Kids with indoor allergies may have flare-ups at certain points throughout the year or may have constant symptoms.