Allergy can be mild as well as severe. Mild allergy can be cured at home but for severe allergy one should contact the doctor. The most severe problem which occurs due to allergy is Asthma.The most common allergens are:Pollens: Pollen grains are very small in size and they appear powdery substance. Different plants have different pollen and there shape and size differs accordingly. Pollen appearance is seasonal so people who are allergic to one or the other allergen are affected by allergy seasonally.Allergic people should know geographical condition of a place before visiting. It is not confirmed that there will be no plans from which a person is allergic.Dust: Most common allergen is dust. Most of the people suffer from dust allergy. Dust settles in house on furniture and other household material. Sometimes outside dust blows with wind and causes allergy.Food Allergy: Some people are allergic to food items like milk, cheese, butter, egg etc. Most common symptoms observed among people suffering from food allergy are: gas, diarrhea, headache, sores in the mouth etc..Pet Allergy: People keeps pet at home for fun but for some people that fun becomes hazardous. Animal dander is one of the common allergen.Chemical allergy: Some chemicals also cause allergy to people. Some people are allergic to smell of perfumes and deodorants. People suffering from one or the other allergy should avoid above mentioned allergens. Allergy can not be treated or cured fully but yes it can be avoided. Till today no permanent solution is available for getting rid of allergy. There is one allergy drug Allegra which is taken by people suffering from various allergies after consulting doctor.Anti allergy drug Allegra should be taken after consulting a doctor. Allegra side effects are not severe but proper precautions should be taken while taking allegra drug.