The symptom spectrum: what's normal, what's serious
A wasp sting delivers venom from the genus Vespula or Polistes into the skin. For most people, the local tissue response — pain, redness, a raised wheal — is the complete reaction. This is not allergy; it's a normal inflammatory response to the venom proteins and is expected in everyone stung. The welt typically peaks at 12-24 hours and resolves within 3-5 days. Large local reactions (LLRs), where the swelling extends significantly beyond the sting site — a sting on the arm producing swelling to the elbow, for example — are more dramatic but are still a local (not systemic) reaction, and are not themselves predictive of anaphylaxis on a subsequent sting. What signals a systemic allergic reaction is the appearance of symptoms at body locations remote from the sting site.
| Reaction type | Symptoms | Response | ER needed? |
|---|---|---|---|
| Normal local | Pain, redness, raised welt at sting site only. Peaks at 12–24 hours. | Ice, antihistamine (diphenhydramine), rest | No |
| Large local reaction (LLR) | Swelling extending beyond sting site, entire limb. May last several days. | Antihistamine, possibly oral corticosteroid if severe. Monitor. | No — unless involves face/throat |
| Systemic/anaphylaxis — mild | Hives or itching distant from sting site, nasal congestion, stomach discomfort, anxiety | Antihistamine IMMEDIATELY; watch closely for progression; if EpiPen available, use it | Yes — go now, even if symptoms seem mild |
| Systemic/anaphylaxis — severe | Throat tightness, difficulty breathing or swallowing, drop in blood pressure, dizziness, loss of consciousness | EpiPen IMMEDIATELY. Call 911. Lay flat with legs elevated unless breathing is laboured — then sitting up. | Yes — 911. Do not drive. |
| Multiple stings (10+) | Toxic reaction from venom volume — nausea, vomiting, low blood pressure, even without prior allergy. Serious in elderly and children. | Call 911. Toxic reactions are not allergy — antihistamines don't help. IV treatment needed. | Yes |
Why the 10-minute window matters
Anaphylaxis is a medical emergency because the timeline from first systemic symptom to life-threatening compromise is short. In the worst-case presentations — usually in people with known severe allergy who receive a sting from a species they're sensitised to — the first sign of throat involvement can progress to complete airway obstruction in under 10 minutes. BC emergency response times outside downtown Vancouver, Burnaby, and Surrey core average 8-12 minutes. This math makes epinephrine (EpiPen) on your person, not in your house, the critical intervention. Every household member with a known or suspected wasp allergy should carry an auto-injector prescribed by their physician, not keep one in a first-aid kit in the kitchen.
EpiPen use: step-by-step
EpiPen auto-injector protocol — wasp sting anaphylaxis
Standard protocol for auto-injector use in a suspected wasp-sting anaphylactic event. EpiPen is epinephrine (adrenaline) — the only medication that interrupts the anaphylaxis cascade reliably. Antihistamines and corticosteroids are adjuncts, not substitutes.
- 1Recognize the triggerWasp sting followed by ANY of: hives or flushing beyond the sting site, throat tightness or difficulty swallowing, shortness of breath, dizziness, nausea, or a 'sense of doom.' Any one of these symptoms following a sting = use the EpiPen now. Do not wait for more symptoms.
- 2Retrieve the EpiPenRemove from carrier. If using EpiPen auto-injector: remove blue safety cap by pulling straight up (not twisting). Hold the device with dominant hand, orange tip pointing down. Do not put thumb over the orange tip.
- 3Inject at the outer mid-thighPress the orange tip firmly against the outer mid-thigh — through clothing is fine. Hold firmly until you hear a click. Continue holding for 3-10 seconds. Remove the device. The orange sleeve will extend to cover the needle.
- 4Call 911 immediatelyEpiPen buys time — it is not a complete treatment. Effects last 10-20 minutes. The ER will administer further medication. Call 911 before the injection if you have hands available, or immediately after. Tell the dispatcher: 'suspected anaphylaxis, wasp sting.'
- 5Position correctlyIf breathing is NOT laboured: lay flat with legs elevated (increases blood pressure). If breathing IS laboured or the person is vomiting: sit up or recovery position. Do not let the person stand or walk — exertion can accelerate systemic collapse.
- 6Second EpiPen at 5-10 minutes if no improvementIf symptoms return or do not improve within 5-10 minutes and you have a second auto-injector, use it in the opposite thigh. Do not delay calling 911 waiting to see if the first shot works.
Antihistamines and corticosteroids: what they do and don't do
Diphenhydramine (Benadryl) and similar antihistamines are the standard treatment for local reactions and large local reactions. They block histamine receptors and reduce the intensity and duration of the local inflammatory response. In mild early systemic reactions, they can slow the progression of hives. What they cannot do: reverse an airway compromise, restore blood pressure, or stop the full anaphylaxis cascade once it's in motion. In BC emergency medicine, antihistamines are used alongside epinephrine in the ER — never instead of it. If you're reaching for Benadryl instead of an EpiPen for systemic symptoms, you are treating the wrong problem. Oral corticosteroids (prednisone) have a similar adjunct role — useful for reducing the risk of a biphasic reaction (a second anaphylaxis wave 4-12 hours later) but not appropriate as a first-line treatment.
After the emergency: allergy testing and future prevention
Anyone who has had a systemic reaction to a wasp sting should be referred for allergy testing by an allergist. Venom immunotherapy (VIT) — a 3-5 year course of injections that desensitises the immune system to wasp venom — reduces the risk of anaphylaxis on subsequent stings from approximately 60% to 5% in good responders. It is covered under BC MSP when prescribed by a specialist following a confirmed anaphylactic event. The BC Anaphylaxis Referral pathway routes through your GP to a provincial allergist; wait times vary by region. In the meantime, the practical prevention protocol is: carry two EpiPens at all times during wasp season (May-October), ensure family members know how to use them, and schedule a consultation with your GP for a BC Anaphylaxis Action Plan card — a laminated card the paramedics can read if you're unable to communicate.
High-risk activities and environments in BC
- Outdoor eating and BBQs in August and September — peak yellowjacket scavenging season. Yellowjackets enter open drink cans and sting the mouth or tongue; this is a high-risk sting location even for people without known allergy because of proximity to the airway.
- Trail work and gardening near ground-level disturbance — yellowjacket underground nests are commonly encountered during digging, mowing, or brush clearing. The nest is disturbed before workers are visible.
- Swimming pools and outdoor water features — yellowjackets are attracted to moisture and frequently sting people using outdoor water.
- Children's summer activities — children are statistically more likely to disturb nests through play behaviour and are less able to recognize and report early symptoms.
- Wasp nest removal attempts — the highest per-event sting risk is DIY nest removal. This is the context in which most multi-sting toxic reactions occur.
For any household where a wasp allergy is known or suspected, removing wasp nests promptly is a genuine medical priority, not a comfort preference. We have provided same-day service for households with anaphylaxis-risk members throughout our service area, including on short notice. If you've had a systemic sting reaction and find a nest on your property, call us — we'll flag it as a priority booking. See also [diy-wasp-removal-risks](/guide/diy-wasp-removal-risks) for the case against self-treatment, and [when-is-wasp-season-bc](/guide/when-is-wasp-season-bc) for the months of peak risk.