An allergic reaction to a sting occurs when your body's immune system overreacts to substances called allergens in the venom of stinging insects such as bees, wasps, hornets, or fire ants.

Minor allergic reactions occur around the site of the sting. This is called a localized reaction, and it can cause pain, itching, redness, swelling, and hives near the site of the sting.

Large local reactions may cause the same symptoms as mild reactions, plus redness and swelling that affects large parts of your body, such as an entire arm or leg.

Systemic reactions are those that spread throughout your body. One type may only involve your skin, causing hives or deeper skin swelling (a cutaneous reaction), but it does not affect the tongue or throat or cause breathing problems. A more serious type of systemic reaction can cause symptoms such as swelling of the tongue, throat, or other body parts.

A life-threatening systemic allergic reaction called anaphylaxis can cause severe symptoms such as confusion, trouble breathing, shock, and sometimes death.

Allergy shots work by putting small amounts of insect venom into your body, making you less sensitive over time to the venom.

Getting a series of allergy shots can prevent a systemic allergic reaction or make it less severe. Allergy shots aren't needed if you have a mild reaction, a large local reaction, or even a systemic reaction that only affects your skin. Only about 4 to 10 people out of 100 who have these kinds of reactions to insect stings go on to have a more serious, anaphylactic reaction.^{footnote 1} This means that 90 to 96 out of 100 people who have localized reactions don't ever have an anaphylactic reaction to an insect sting.^{footnote 1}

Allergy shots can greatly reduce your risk of having another life-threatening reaction if you've had one before. Imagine a group of 100 people who have had a life-threatening reaction. Without allergy shots, up to 60 of those 100 people will have another life-threatening reaction in the future. But if those 100 people get allergy shots, only 5 of them will have another life-threatening reaction.^{footnote 1} This treatment is most effective after an entire course of allergy shots is complete.

After allergy tests have identified any insects you are allergic to, you can begin to get the shots. At first, you will get weekly shots of small doses of venom and allergens from the insects that cause your allergies. After about 4 to 6 months of weekly shots, you will get a regular dose, called a maintenance dose, every 4 weeks for 3 to 5 years, depending on the type of stings that cause your allergies. For example, fire ant allergies require longer treatment than other stinging insect allergies.

If you have had severe reactions to insect stings in the past, you may want to get a series of allergy shots on a faster schedule, called "rush immunotherapy." For this you get allergy shots every few hours on one day or every few days. This helps to rapidly increase your tolerance to an allergen. After the first shot, you must wait to see if you have a reaction to the shot. If you don't have a reaction, you get more shots throughout the day. You (or your child) may feel anxious about receiving the next shot. So it may help to bring a book or something to distract you while you wait. Rush immunotherapy is usually done by a specialist. Having a severe reaction to this treatment is more likely than with standard allergy shots.

This treatment usually works in 1 to 8 days instead of the standard treatment, which takes several months. You may have this "rush" treatment if you have severe or life-threatening allergic reactions to insect stings, are a long distance from any type of health care center, or are about to travel.

Allergy shots are safe for most people. The most common side effects are redness and warmth at the injection site. Some people may have large local reactions that include itching, hives, or swelling of the skin near the injection site.

But allergy shots can trigger a more serious reaction, which may include trouble breathing or swelling in the deep layers of the skin. In rare cases, a person may have a life-threatening allergic reaction (anaphylaxis) to the shots. Because of this, the shots are given in a clinic or other health care setting where emergency care can be provided if needed.

Talk with your doctor if you have an autoimmune disease (such as lupus) or are taking medicine for heart problems (such as beta-blockers or ACE inhibitors). Allergy shots may not be safe for you.

Your doctor may advise you to have allergy shots for insect stings if:

• Allergy tests showed that you are sensitive to allergens from the venom of one or more insects.
• You had a life-threatening allergic reaction to an insect sting.
• You have anaphylactic reactions to insect stings but cannot carry epinephrine with you at all times.
• You work outside and have worse reactions each time you are stung.
• You have only been stung once but had a moderate to severe reaction.

• Allergy tests showed that you are not sensitive to allergens from the venom of insects.
• You have an autoimmune disease (such as lupus) or are taking heart medicine (such as beta-blockers or ACE inhibitors).
• Your allergic reaction to insect stings doesn't cause an anaphylactic reaction.
• You are younger than 16 and had a mild skin reaction all over your body (cutaneous reaction) without any other symptoms.
• You tried allergy shots before, but the shots triggered a moderate to severe allergic reaction.