Stinging Insect Allergy, Normal vs. Severe Reactions

Hundreds and thousands of people go to hospital emergency rooms (ER) or urgent care (UC) facilities seeking for medical help for insect stings every year, although most people are not allergic to insect stings.  Understanding sting insect allergies is important so people will be able to recognize the difference between a normal insect sting reaction and a severe, potentially life-threatening allergic reaction, will seek medical care accordingly, and reduce unnecessary anxieties, medical expenses, and medications. 

General Facts

It is estimated that up to 0.8% of children and 3% of adults may develop potentially life-threatening, severe systemic allergic reactions to insect stings. In the US, approximately 40 deaths each year in the United States are a direct result of stinging insect allergies. The sting insects that most commonly cause allergies in the United States include yellow jackets, hornets (yellow hornets and white-faced hornets), wasps, honey bees, and in the southern Unites States, fire ants.

Common Reaction Patterns and Symptoms

Recognizing the common patterns and associated symptoms after being stung by an insect will help you better understand what type of reaction you may be experiencing,  guide you on when to ask for help or seek care, and determine  the treatment you may need.

1. Normal reaction

• Also called local reaction, normal reaction is the most common reaction people encounter when they’re stung by a stinging insect.   
• Normal reaction includes pain, itching, swelling and redness confined to the sting site.

2. Large local reaction

• In addition to the local symptoms, swelling larger than 10cm in diameter is considered a large local reaction.
• People will notice an increase in size over the course of 24 to 48 hours.
• Symptoms typically take 3 to 10 days to disappear.

3. Systemic reaction

• A systemic reaction includes a range of different reactions and manifestations in the body, not limited to the site of the sting, with symptoms ranging from mild to life-threatening.
• Reactions affecting the skin such as hives, swelling, itching, flushing
• Bronchospasm, when your chest tightens and it becomes difficult to breath.
• Upper airway obstruction such as  tongue or throat swelling/closing
• Low blood pressure and cardiac shock
• Gastrointestinal including nausea, vomiting, or abdominal cramping

Key Takeaway #1

1. Most insect stings result in local reactions which are non-allergic and non-life threatening.
2. Although alarming in appearance, large local reactions are often treated the same way as normal reactions.  Only unusual painful or a very large local reaction may need medical attention.
3. Alternatively, any systemic reaction requires medical attention. 

Symptoms of a severe reaction:

Symptoms may include 2 or more of the following:

• Generalized itching or flushing
• Hives and swelling in the area other than the sting site
• Swelling of the tongue or throat
• Hoarseness or difficulty swallowing
• Chest tightness and difficulty breathing
• Abdominal cramping, vomiting, nausea or diarrhea
• Dizziness, fainting or a rapid drop in blood pressure
• Loss of consciousness or cardiac arrest

Key Takeaway #2

1. If you experience either one or a combination of the above symptoms after you get stung by a flying insect, it’s very likely that you’re developing an allergic reaction to the insect sting.
2. If you experienced such symptoms by a stinging insect in the past, you should know that you not only had an allergic reaction to the insect sting, but also carry a 60% higher risk of similar or worse reaction if stung again.  Therefore, you need to see an allergist, for further evaluation and management for your insect sting allergy.
3. A severe allergic reaction to an insect sting is a medical emergency; immediate medical attention is required.

Diagnosis: insect sting allergy testing pros and cons

Diagnosing an insect sting allergy is based on your detailed history of post sting symptoms and supportive allergy testing. Your allergist can then provide treatment options in the case of future stings.

• Prick and under the skin tests are the preferred method of insect sting allergy testing
• A serum sting insect specific immunoglobulin E (IgE) or radioallergosorbent test (RAST) can be used, but false-negative results occur in 15% of cases when testing with this alone. In order to confirm the diagnosis and if insect venom immunotherapy (allergy shots) is needed, a prick and intradermal skin test would still be necessary regardless of the RAST result.
• RAST, on the other hand, is indicated if there is a clear history of sting anaphylaxis but skin test results are negative.

Key Takeaways, Diagnostic Testing

1. Since false positive skin or RAST test results are present in more than 20% of healthy adults, insect sting allergy testing (skin or RAST) should not be used for general screening.
2. Normal, local, and large local reactions are not indicated for insect sting allergy testing.

Management and Treatment

Treating an insect sting allergy is divided into 2 important parts: preventive treatment measures for underlying allergy and symptomatic care when a sting occurs.

1. Symptomatic Care

• For normal or local reactions, gently clean the sting area with soap and water, remove the stinger with a scraping motion if there is one, and apply a cold compresses to the sting site.  You may also take oral antihistamines and use topical steroid ointments to relieve itching and swelling.
• For severe systemic reactions, call 911 ASAP for help if you have no previous history of sting insect allergy and do not carry an epinephrine auto-injector (EpiPen).  Otherwise, use the EpiPen as soon as signs of severe allergic reaction occur and then call 911 or have someone take you to the emergency room if you get stung. 

Key Takeaway #4

1. For a severe insect sting allergic reaction, the drug of choice is Epinephrine or EpiPen (not Benadryl or corticosteroid)!
2. Epinephrine (EpiPen) is a rescue medication only, after the epinephrine (EpiPen) is used, you need to call 911 or go to the nearest hospital for further evaluation even if your symptoms have improved after a single dose of EpiPen.
2. Preventive treatment
3. Venom immunotherapy (VIT)

• Highly effective, long-term preventive treatment of sting insect allergy
• Involves different doses of venoms given to the patient to desensitize  them (VIT is 98% effective)
• Therapy lasts 3 to 5 years

2. Avoidance

• Different insects have different nesting and behavior characteristics, avoid them accordingly.
  • Yellow jackets build nests in the ground; Hornets build large nests in trees and shrubs, and wasps build honeycomb nests in shrubs and under eaves of houses or barns.
• Avoid wearing sandals or walking barefoot during yard work, farming or gardening.
• Avoid drinking from open beverage cans outdoors or using any sweet smelling perfumes or colognes.
• Avoid wearing bright-colored clothing.

Bottom line

• Most people are not allergic to insect stings.  The most common reaction to an insect sting is a local or normal reaction.
• Systemic allergic reaction to insect sting, regardless of severity, needs medical attention.  A severe allergic reaction is a medical emergency.
• Normal and large local reactions are not indicators of an insect sting allergy and general insect sting allergy screening is discouraged.
• EpiPen is the drug of choice for life-threatening insect sting allergic reactions.  It needs to be carried at all times for patients with a history of severe insect sting allergies.
• There is a long-term protective treatment readily available, venom immunotherapy, VIT.  It is up to 98% protective and not only improves symptoms, but your quality of life
• All and all, if you think you may be allergic to insect stings, speak with your allergist. They’ll be able to address your concerns and determine the best course of action.