You have asked a general query about allergic reaction. First and foremost thing you need to do is to stay away from the substance causing allergy. In food allergies, avoiding the allergen is a life-saving necessity. That's because, unlike allergies to airborne particles that can be treated with shots or medications, the only way to treat food allergies is to avoid the allergen entirely. For example, people who are allergic to peanuts should avoid not only peanuts, but also any food that might contain even tiny traces of them. Avoidance can help protect people against non-food or chemical allergens, too. Eliminating exposure to an allergen is enough to prevent allergy symptoms and they don't need to take medicines or go through other allergy treatments. Here are some things that can help you avoid airborne allergens: 1) Keep family pets out of certain rooms, like your bedroom, and bathe them if necessary. 2) Remove carpets or rugs from your room (hard floor surfaces don't collect dust as much as carpets do). 3) Don't hang heavy drapes, and get rid of other items that allow dust to accumulate. 4) Clean frequently (if your allergy is severe, you may be able to get someone else to do your dirty work!) 5) Use special covers to seal pillows and mattresses if you're allergic to dust mites. 6) If you're allergic to pollen, keep windows closed when pollen season's at its peak, change your clothing after being outdoors ? and don't mow lawns. 7) Avoid damp areas, such as basements, if you're allergic to mold, and keep bathrooms and other mold-prone areas clean and dry.