Allergies can be incredibly annoying and very serious. Some symtoms may include red eyes, sneezing, shortness of breath, swelling, a runnynose, and more.
What are you allergic to?
From what i remember my doctor said i was generally alergic to the dust and unfiltered air. But some other common allergens are pollen and certain types of food like peanuts.
Are allergies medically related, hereditary or ?
There is a hereditary predisosition to allergies called atopy so it definitely can be hereditary! 
Are they any cure for allergis?
A lot of doctors do things to treat and reduce allergies rather than cure them i have not heard of actually completely getting rid of allergies but redicing the heavy response to them. Unfortunately
So what are the common things people are allergic to?
Reducing* apologize for my typo. Common things are dust, mold, pollen, and for food cow's milk, eggs, fish, tree nuts, soy, rice, wheat, fruit, shellfish, and more and more!