Sometimes it’s difficult for patients to be able to tell the difference between a normal reaction and a true allergic reaction when they are stung by an insect. So how can you tell the difference? Here are a few pointers to help you to know which kind of a reaction you or your loved one is having.
Bee, wasp, yellow jacket, hornet, or fire ant stings are the insect stings that most often trigger allergies. However, most people are not allergic to insect stings and may mistake a normal sting reaction for an allergic reaction. By knowing the difference, you can prevent unnecessary worry and visits to the doctor.

The severity of an insect sting reaction varies from person to person. There are three types of reactions — normal, localized, and allergic:
• A normal reaction will result in pain, swelling, and redness around the sting site.
• A large local reaction will result in swelling that extends beyond the sting site. For example, a person stung on the ankle may have swelling of the entire leg. While it often looks alarming, it is generally no more serious than a normal reaction. Large local reactions peak at approximately 48 hours and then gradually resolve over 5 to 10 days.
• The most serious reaction to an insect sting is an allergic one. This condition requires immediate medical attention.

A severe allergic reaction (anaphylaxis) to bee stings or other insects is potentially life-threatening and requires emergency treatment. A small percentage of people who are stung by a bee or other insect quickly develop anaphylaxis. Signs and symptoms of anaphylaxis include:
• Skin reactions, including hives and itching and flushed or pale skin
• Difficulty breathing
• Swelling of the throat and tongue
• A weak, rapid pulse
• Nausea, vomiting or diarrhea
• Dizziness or fainting
• Loss of consciousness

Treatment for minor reactions
To sting, a bee jabs a barbed stinger into the skin. Removing the stinger and its attached venom sac right away will keep more venom from being released.
• Remove the stinger as soon as you can, as it takes only seconds for all of the venom to enter your body. Get the stinger out any way you can, such as with your fingernails or a tweezer.
• Wash the sting area with soap and water.
• Apply cold compresses or ice to relieve pain and ease swelling.

Treatment for moderate reactions

The following steps may help ease the swelling and itching often associated with large local reactions:
• Remove the stinger as soon as possible.
• Wash the area with soap and water.
• Apply cold compresses or ice.
• Apply hydrocortisone cream or calamine lotion to ease redness, itching or swelling.
• If itching or swelling is bothersome, take an oral antihistamine that contains diphenhydramine (Benadryl) or you can take another kind of anti-histamine such as Zyrtec or Allegra.
• Avoid scratching the sting area. This will worsen itching and swelling and increase your risk of infection.

Emergency treatment for allergic reactions

During an anaphylactic attack, an emergency medical team may perform cardiopulmonary resuscitation (CPR) if you stop breathing or your heart stops beating. You may be given medications including:
• Epinephrine (adrenaline) to reduce your body’s allergic response
• Oxygen, to help you breathe
• Intravenous (IV) antihistamines and cortisone to reduce inflammation of your air passages and improve breathing
• A beta agonist (such as albuterol) to relieve breathing symptoms

If you find you are allergic to bee stings, contact your doctor. They will likely prescribe you an epinephrine autoinjector (Epi-pen). You should carry it with you at all times in the event you are stung. Also make sure you understand how to use your Epi-pen. If you have questions, ask your doctors office or your pharmacist.
If you think you may be allergic to insect stings/venom, let your doctor know right away. You can talk to your doctor about the possibility of immunotherapy (allergy shots), which could help make you less allergic to these insect stings.

References
https://www.aaaai.org/conditions-and-treatments/allergies/stinging-insect-allergy.aspx
http://www.mayoclinic.org/diseases-conditions/bee-stings/basics/symptoms/con-20034120
http://www.webmd.com/allergies/guide/insect-stings