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Side Effects of Allergy Shots

written by: Kaye Morris • edited by: Tania Cowling • updated: 10/5/2010

If you spend part of each year sneezing and coughing, you're probably part of a large group of people who suffer from seasonal allergies. If you're one of the unfortunate individuals that does not respond well to allergy medication and are considering allergy shots, you should be aware of the risks.

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    Why Allergy Shots May Cause Side Effects

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    Before treatment begins, you undergo extensive allergy testing that identifies all the substance(s) that create an allergic reaction in your body. The doctor then constructs allergy shots with small amounts of the substance(s) that cause you to have an allergic reaction. By injecting small amounts of the allergens into your body at scheduled intervals, your immune system can slowly build up a tolerance to the allergens. Once your immune system has had a reasonable amount of time to build a tolerance to the injection, the doctor will increase the allergens in the allergy shot to further boost your immune system. It can take years of allergy shots and many increases in the allergen content before you've achieved enough reduction in your allergy problems to cease the injections. Essentially, the risk for allergy shots side effects exists because the doctor is directly introducing allergens into your system.

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    Skin Irritation

    The most common allergy shots side effect is skin irritation. Your skin may become red, swollen, itchy or irritated at the injection site due to the contact of the needle containing the allergens. Although the symptoms usually disappear within eight hours, you can apply calamine lotion or other soothing items to the injection area to help ease the itching. Avoid scratching the area so you do not damage your skin. If the itching is so bad it's distracting or uncomfortable, ask your doctor if you can use cortisone cream to alleviate the itching. A cold compress applied directly to the injection site may also reduce skin irritation and itching.

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    Systemic Reaction

    A systemic reaction occurs when the effect of an agent moves through multiple organs and/or systems in your body. Allergy shots may cause mild systemic reactions such as sneezing, hives and nasal congestion. If your reaction to the allergy shot is more severe, you may experience swelling in your throat, wheezing when breathing and/or tightness in your chest. Systemic reactions generally occur within 30 minutes of receiving your shot, which is why doctors usually insist you remain in the office for that period of time after the shot is administered. If you experience a systemic reaction to an allergy shot, let your doctor know so he can deal with the reaction in the best manner possible.

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    The rarest reaction to an allergy shot is anaphylaxis, which is an allergic reaction that incorporates the entire body. Anaphylaxis will develop within minutes of the injection, and includes symptoms such as abdominal pain, difficulty breathing or swallowing, dizziness and nausea. If not treated quickly, anaphylaxis can be deadly. Alert your doctor immediately if you experience any of those symptoms following an allergy shot.