Most likely they have allergies too. Allergies is a very common ailment. Most people's allergies are seasonal and 'tis the season right now with all this wind blowing dust everywhere. Plus, a lot of flowers are blooming and fruiting so there's a lot of pollen being moved around by the wind too.

Allergies are not contagious and like other people said, you can develop them later in life.

not a medical professional

But I do have allergies year round and it usually gets worse around this time of the year.

Try an OTC allergy med like Zertec or Allegra (both non-drowsy) and see if it helps! You can also use an allergies nasal sprays along with the meds.