1. What things are likely cause allergies? Everyday common things such as environmental allergens like house dust mites, plant pollen, animal dandruff, spores; foods like nuts, fish, egg, milk or drugs usually causes you the allergic reaction and symptoms. 2. Can I develop allergy at any age? Many of allergies develop in the childhood and they may remain dormant until reactivated in adult life. So, it can be presented at childhood or at an adult age. for more: http://www.microenthospital.com/faqs-3/