A mild winter and a wet, warm spring mean greater numbers of queen wasps – up to twice the size of average wasps – will likely survive the winter. As they seek new sites to establish a nest, a testing expert says more people will be at risk of a reaction to wasp stings this month.

More queen wasps will likely survive hibernation because of the UK’s mild winter and damp but warm spring. At up to twice the size of the worker wasps that plague picnic tables in August, it’s not difficult to spot springtime queen wasps. April is the peak month when they seek out new places to set up a nest, so there is growing concern that we face a period of increased contact.

Leading testing expert Dr Avinash Hari Narayanan (MBChB), clinical lead at London Medical Laboratory, says: “The successful overwintering of an abnormally high number of queen wasps, who have hibernated in trees, sheds and roofs, is potentially serious news. More wasps mean it’s more likely that people will be stung. In turn, this increases the chances of severe allergic reactions or, in rare cases, anaphylactic shock.”

“Many of us don’t expect to encounter wasps in the spring. We think of them as late summer insects. But the truth is that we are most likely to encounter the largest wasps in April and May. Queens usually measure around 2-2.5cm in length, whereas workers measure approximately 1.2-1.7cm.”

“Queen wasps generally fly low to the ground, searching for holes in trees or crevices within buildings to set up their nests. They may not find a suitable natural spot in built-up areas, so your home may provide a good alternative. Undisturbed places, such as lofts and attics, are a favourite.”

“Due to her relatively larger size, the queen wasp’s sting is slightly bigger. However, it’s not considered more dangerous than the smaller worker wasp. For most of us, a wasp sting is painful but not fatal. However, an increasing number of UK adults, around 21.3 million, now suffer from at least one allergy. That could mean they potentially develop a severe allergic reaction to wasp venom, termed “anaphylactic shock”. This is a serious, potentially fatal, medical condition that can be discovered through allergy testing.”

“Just because a person has been stung once without significant reaction does not mean they will be alright the next time. As with most allergies, the first exposure sensitises our body to a particular allergen, so the second time we are stung, the reaction could be far worse. People with a severe allergic reaction to a wasp or bee sting have a 25-65% chance of anaphylaxis the next time they are stung.”

There are several warning signs to look out for if a sting is producing a more severe problem, such as anaphylactic shock:

• A sudden feeling of weakness (caused by a drop in blood pressure)
• Dizziness
• A sense of fear or dread
• A rapid pulse
• Swelling of the airways and throat, making it difficult to breathe
• Swelling of the lips, eyelids and facial features
• Severe asthma
• Itching and swelling away from the site of the sting
• Stomach cramps and/or a feeling of sickness

“Fortunately, there is an effective way people can learn in advance if they are likely to develop a severe reaction to a sting. A simple finger-prick allergy test is the fastest, safest and most convenient way to establish if someone may be allergic to stings from bees and wasps. The test can also detect nearly 300 other potentially severe allergies, including dairy, seafood, sunflower seeds and nuts, pet hair, house dust mites and even latex.”

“The test grades people’s reaction to many common and less familiar potential allergens from 0 to 4. A level 4 result indicates high sensitisation has occurred, which could mean a reaction such as an asthma attack or anaphylactic shock may occur if they are exposed to the substance again.”

“People who discover they are at risk of a severe reaction must inform their doctor. They may be prescribed a potentially life-saving, pre-loaded adrenaline injection device such as an EpiPen.”

“For anyone concerned about their future reaction to a sting, as well as certain foods or other allergens, London Medical Laboratory’s Allergy Complete is the UK’s most comprehensive allergy test, analysing 295 allergens. It can be taken at home through the post or at one of the many drop-in clinics across London and nationwide in over 95 selected pharmacies and health stores.”