A wasp's sting is its defense mechanism. Short and sharp, it’s meant to make you leave the insect alone. Some pain, redness and swelling is normal afterward. But for someone with wasp sting allergy this can spread beyond the puncture spot and last up to a week. A severe allergic reaction to the venom can be life-threatening.

Read more about wasp allergy, the symptoms, how to treat them and when they’re most likely to happen.

Wasp stings tend to happen most in late summer and fall. That’s the riskiest time for an allergic reaction. Queen wasps emerge from hibernation to build a nest in the spring. The colony expands and peaks over the summer. There are no jobs to do in the nest after that. Instead wasps roam looking for sugary foods. You might notice them paying even more attention to your picnic.

Yellow jackets are a type of wasp too and have a similar life cycle. Scientists call their erratic late summer behavior “delirium”. It’s why yellow jackets also tend to sting more, triggering insect sting allergy, in August and September.

Wasp allergy season comes to an end when temperatures drop and the entire colony dies.

Allergic reactions to wasps tend to be more than four inches across. They can make your whole arm or leg swell up, not just the sting site. The redness could be more pronounced too but may be harder to see on darker skin types. These large local allergic reactions can last a week and are often treated in the same way as a normal sting. That is, with basic first aid, of which more below.

If the redness, swelling or hardening of the skin around the bite gets worse over 24 to 72 hours, be sure to see your healthcare provider as soon as possible.

Wasps and honeybees can look a lot alike, especially in a moment of panic. Both collect nectar and have a similar shape. But there are important differences too:

Insect sting allergy can cause a severe systemic allergic reaction called anaphylaxis. It’s less likely with wasps than bee stings but it’s still important to know the common symptoms. Call an ambulance if you spot any of these signs:

• Flushed, pale or itching skin
• Hives
• Digestive issues including nausea, diarrhea or vomiting
• Feeling dizzy or fainting
• Hypotension (low blood pressure)
• Fast or weak pulse
• Restricted airways and a swollen throat or tongue, which may cause wheezing and trouble breathing

Anaphylactic shock is the most serious possible reaction. You may feel faint and even pass out because of a sudden drop in blood pressure. It can be life-threatening and needs immediate medical attention.

Insect sting anaphylaxis can happen suddenly, in minutes or up to a few hours after the first reaction. But other wasp allergy symptoms may not be immediate. Sometimes large local allergic reactions develop hours afterwards and go on building for one or two days. There have also been reports of delayed reactions as much as five days after multiple wasp stings, although this is rare.

The substances or allergens that can cause reactions to wasp stings are particular proteins in the venom. Scientists have identified six wasp venom allergens. You need to be stung by a wasp at least twice to develop an allergy. This is due to a process called sensitization.

The first time, your immune system registers the wasp venom as a threat. It produces Immunoglobulin E (IgE) antibodies for that allergen. You’re sensitized now and may develop an allergy. Not everyone does and scientists don’t yet know why that is.

Wasp spray does kill them indoors but be careful not to breathe it in. Outdoors, repellents for skin and clothes don’t tend to work well on stinging insects. So here are some tips for avoiding stings during wasp allergy season.

    1. Smells

• Choose unscented toiletries including sunscreen and avoid sweet-smelling perfumes
• The scent of banana is especially attractive

    2. Clothes

• Go for neutral rather than brightly colored clothing or flowery prints but avoid black
• Wear summer sandals with closed toes
• Cover as much skin as possible

    3. Food and drink

• Keep kitchen surfaces clean and put leftovers away
• Drink from a screw top bottle at picnics rather than a can and put the cap back on between sips
• Cover food outdoors
• Pick fruit as soon as it ripens in your garden and don’t leave windfalls to rot and attract wasps

    4. Keep calm

• Never swat a wasp as it can make them release an alarm pheromone to call other wasps to help
• Keep still if you spot a single wasp flying around
• If there are lots of them move into the shade
• Quickly open car windows to let a wasp out or pull over and open the doors

An ice pack or cold compress may be all that’s needed for wasp stings, even large local reactions. An over-the-counter painkiller can help relieve discomfort. Calamine lotion, corticosteroid cream or an oral or topical antihistamine may also help ease your symptoms. Particularly painful or widespread swelling may need medical attention and prescription antihistamines or corticosteroids.  

Because of the risk of anaphylaxis your healthcare provider is likely to prescribe an epinephrine auto-injector. Epinephrine is another name for adrenaline. The advice is to carry two auto-injectors at all times. This is emergency treatment for you to use in the event of severe reactions. You should also seek immediate medical attention, even if you use your auto-injector, in case you have a delayed secondary reaction.

Wearing a medical alert bracelet will tell people you’re allergic to insect stings so they know how to help you.

Not yet but there is a treatment. Venom Immunotherapy (VIT) may be right for you if you’ve had a large local skin reaction or anaphylaxis. The goal is to desensitize your immune system and reduce the risk of severe insect allergy symptoms. Treatment involves regular tiny doses of wasp (hymenoptera) allergen. A full course takes three to five years. Your doctor or allergist can tell you more.