Y does one develop allergies to fruits/vegetables all of a sudden? N can it be cured without the use of medicine?

Allergies. Food allergy can manifest at any age, but you mention fruit and vegetable. Is it only with fresh/raw fruits and veggies? Is it only in your mouth with itch, tingle, slight swelling? Goes away quickly? If so, then this is something known as oral allergy syndrome. Read up on this syndrome to see if this is your problem. If not, then you really should see your doctor or an allergist.