Whether you suffer from indoor allergies or outdoor allergies, you probably take medications to help you manage your symptoms. Inside your body there is a mast cell which causes allergic reactions (symptoms such as sneezing, itchy eyes, or runny nose) by releasing chemicals into your body when it comes into contact with an allergen.

Corticosteroids

Corticosteroids are a prescription-strength medication that block allergic reactions in order to prevent inflammation. Corticosteroids stop allergic reactions by reducing the size and quantity of cells in your body that produce the allergic reactions.

Antihistamines

Antihistamines are medicines that block histamine, which your immune system releases when it comes into contact with an allergen. Histamine causes symptoms such as itchy, watery eyes and runny nose. Antihistamines prevent the mast cell from being affected by the allergen, so the histamine cannot be released.

Decongestants

Decongestants help clear blocked nasal passages as a result of allergic reactions. Decongestants do not stop an allergic reaction; instead, they help you manage your symptoms after a reaction has occurred.

Allergy Shots

Allergy shots contain allergen extracts. You get them over a period of a few years in the hope of reducing your body's reaction to the allergens in the shots. By taking the allergen extracts into your body a little at a time, you can build up a resistance to them slowly. Eventually the hope is that you will no longer react when you encounter these allergens in the real world.

Emergency Medications

Emergency epinephrine is given for severe allergic reactions to things like peanuts or bee stings. The epinephrine shots are a form of adrenaline; when you inject it into your body it helps to slow down your body's reaction to the allergen and buys you some time to get to the hospital for more treatment.

Source:

Mayo Clinic: Allergy Medications: Know Your Options

Mac: Allergy Medications Explained