Normal Sting Reactions vs Allergic Reactions
It is important to distinguish between a normal reaction to an insect sting and a true allergic reaction:
| Reaction type | What it looks like | Action needed |
|---|---|---|
| Normal local reaction | Pain, redness, swelling at sting site. Resolves within hours. | Ice, antihistamine if needed |
| Large local reaction | Swelling extending >10 cm from sting site, lasting 1–2 days. Uncomfortable but not systemic. | Antihistamine, GP assessment if severe |
| Systemic allergic reaction | Symptoms away from sting site: hives, throat swelling, dizziness, vomiting, or collapse. | Emergency treatment; GP review; consider testing and EpiPen |
Venom Allergy: The Mechanism
Venom allergy is an IgE-mediated allergic response to proteins in bee or wasp venom. On a first sting, the immune system is sensitised and produces IgE antibodies specific to venom components. On subsequent stings, these antibodies trigger mast cell degranulation, releasing histamine and other mediators — producing the systemic allergic reaction.
Key venom allergen components include:
- Bee (Apis mellifera): Api m 1 (phospholipase A2) — the major bee allergen; Api m 2, Api m 3, Api m 10
- Common wasp (Vespula vulgaris/germanica): Ves v 5 (antigen 5) — the major wasp allergen; Ves v 1 (phospholipase A1)
ALEX3 tests IgE against these specific venom components, allowing confirmation of which insect(s) you are sensitised to and whether the sensitisation is genuine or cross-reactive.
Who Should Be Tested?
ALEX3 venom testing is appropriate if you have experienced a systemic reaction after a bee or wasp sting and want to:
- Confirm which insect(s) you are sensitised to (especially if you are unsure what stung you)
- Assess the degree of sensitisation
- Obtain evidence to support referral for venom immunotherapy (desensitisation)
Testing is generally timed at least 4–6 weeks after the reaction, as IgE levels may temporarily fall immediately after anaphylaxis. Your GP will advise on the best timing.
After a Sting Reaction: What to Discuss with Your GP
If you have had a systemic reaction to a sting, your GP should:
- Prescribe an adrenaline auto-injector (EpiPen or Jext) as a precautionary measure
- Arrange venom IgE testing (ALEX3 or specific IgE)
- Consider referral to an NHS specialist allergy clinic for venom immunotherapy assessment
Venom immunotherapy (VIT) involves a course of injections over 3–5 years and reduces the risk of anaphylaxis from future stings by over 90%. It is one of the most effective treatments in allergy medicine and is available through NHS allergy centres.
Book Allergy Testing
Lambert Medical offers ALEX3 allergy testing which includes insect venom components alongside 300+ food and environmental allergens. If you have had a concerning reaction to a sting, book an appointment with our GP for assessment and testing.