When you get an allergy shot, your allergist or doctor injects small doses of substances that you are allergic to (allergens) under your skin. This helps your body “get used to” the allergen, which can reduce or prevent symptoms.
At first, you may need to get allergy shots once a week and then once a month. It may take up to a full year of shots before you see any change in your symptoms.
The allergy shot may cause mild problems, such as soreness, redness, warmth, or swelling on the arm where you got the shot. It may also cause itching, hives, or a rash that spreads to other parts of your body.