Allergy Triggers: 9 Common Things That Causes Allergies.
Allergic reactions occur when our body’s defenses mistakenly react to typically harmless substances like pollen, animal dander, or food, ranging from mild to severe symptoms and can even be life threatening. In the US, around 30% of adults and 40% of children experience allergies. Here are some common allergy trigger.

References:
https://www.webmd.com/allergies/ss/slideshow-common-allergy-triggers