What is insect bite allergy?
Insect allergy affects between 1% and 7% of the global population. Most cases are made up of insect sting allergy to bees, wasps, hornets, yellow jackets and other common stinging insects. But biting insects like mosquitoes and horseflies can trigger allergy too.
Occasionally an insect bite can cause a life-threatening reaction called anaphylaxis. In this article we’ll look at insect bite allergy and give you advice on how to avoid getting bitten.
What is insect bite allergy?
Biting insects tend to be after your blood. That’s their breakfast, lunch and dinner. Some have piercing mouthparts (like mosquitoes). Others tear the skin (midges and horseflies). Most people get redness, itching and minor swelling around the bite which tends to get better in hours or days.
If you have an insect bite allergy, it’s not the piercing or puncturing that cause the reaction. Your immune system spots one or more proteins (allergens) in the insect’s saliva which it thinks could be harmful to you. It creates Immunoglobulin E (IgE) antibodies as a defence. Now you’re sensitised and may go on to develop an insect bite allergy. In which case, the IgE antibodies tell other cells to release certain chemicals, like histamine, the next time you get bitten. And that may cause allergy symptoms.
Which insects cause insect bite allergy?
Common biting insects known to cause an allergic reaction include:
- Mosquitoes – an allergic reaction to proteins in mosquito saliva can cause swelling, heat and redness. It starts within hours of a mosquito bite. This rare allergic reaction is called skeeter syndrome
- Bed bugs – larger than usual bite marks and painful swelling
- Fleas – often multiple bites that can cause skin irritation like an itchy rash (dermatitis)
- Biting midges – can cause local allergic reactions
- Flies – horseflies, black flies and tsetse flies may in rare cases cause local skin reactions
- Ants – some ants can bite and sting (only the female has a stinger).
- Ticks – technically ticks are not an insect but arachnids, related to spiders. Because they bite they're often grouped together with biting insects that can cause allergies. Repeated tick bites can lead to allergic reactions and itching and swelling.
Tick bites can also cause a rare type of food allergy. The tick’s saliva can sensitise you to beef, lamb, pork and venison. You may get allergy symptoms four to eight hours after eating these types of red meat. The reaction can be severe and needs immediate medical attention.
What are the symptoms of insect bite allergy?
An insect bite allergy can cause allergic reactions around the bite or elsewhere in the body. It’s normal for everyone to get:
- pain (stinging sensation but not from stinging insects)
- redness (this can be harder to see on darker skin)
- itching
- local swelling around the bite
Biting insects can cause bumps or swellings on the skin whether you have an insect allergy or not. A papule is a small raised area of skin that develops up to 24 hours after a bite. It usually lasts a few days and may have some redness around it. A wheal is a red swollen mark that may develop straight after being bitten and stay for a few hours. Within the next day or so, you may get a slightly more persistent itchy solid lump.
Insect bite allergy: Severe reactions
Mosquitoes and horseflies are the biting insects most likely to cause anaphylaxis. But severe allergic reactions are much less common than with insect sting allergy. Symptoms that are part of a more serious reaction and a medical emergency include:
- skin feels clammy
- lightheadedness, fainting or losing consciousness
- fast heartbeat
- wheezing and difficulty breathing like fast or shallow
- anxiety or confusion
Your body may also go into shock. Anaphylaxis can happen suddenly, in minutes, or up to a few hours after you’re stung and can be life threatening. You should seek medical attention immediately. Also, having a severe reaction increases the risk of it happening in the future.
Diagnosing an insect bite allergy
Your GP can help if you think you have an insect bite allergy. They will note your medical history along with your worst bite reaction. This is to help predict the likelihood of a serious allergic reaction in the future which may need emergency treatment. They will also want to know details of the insect that bit you. A photo can be helpful if you’re able to take one on your phone.
A skin prick test or blood tests might also be necessary to help make a diagnosis.
How do you prevent insect bite allergy symptoms?
As with insect stings, prevention is the best way to avoid insect bite allergy symptoms. Insect repellents with DEET, icaridin or lemon eucalyptus oil can work against biting insects. Just remember to put it on after sunscreen if using that too. You can also try these tips:
- wear long sleeved shirts and trousers rather than shorts
- choose neutral colours rather than bright clothing
- cover exposed skin if you’re outside at sunrise or sunset when insects tend to be most active
- spray insect repellent over clothes, shoes, socks and camping gear to deter mosquitoes
- avoid compost, ponds and stagnant water where mosquitoes and horseflies are often found
- use window and door screens or a mosquito net with at least 24 holes per square centimetre
- look out for ticks in any grassy, bushy or wooded area including your garden
- check your clothes and pets for ticks when you get home, and take a shower
And always call pest control to remove wasp or yellow jacket nests, and to clear bed bugs from your home.
Is there a link between insect bite allergy and stinging insects?
There isn’t enough evidence yet to prove a link between stinging insect allergy and an allergy to biting insects. Cross-reactions happen when your immune system spots proteins that are very like your trigger. And there does seem to be some commonality between insect venom and saliva that may involve honeybees and wasps. But more research is needed.
Many of the allergens in the saliva of biting insects are common to many species and could also cause cross-reactions. Others are specific to a certain type or types of the same insect, for instance mosquitoes. That may be because insects in different places evolved differently depending on which animal they fed from.
How do you treat an insect bite allergy?
Most insect bites just need an ice pack or cold compress to calm the itch (if anything). Brush the insect off first if it’s still attached to your skin.
Be careful if it’s a tick though. Grab the pest as close as possible to your skin and pull it away without squeezing. And be careful to remove the tick’s mouth parts. Use tweezers or a tick remover. Afterwards, wash the bite with soap and water. Then apply antiseptic cream.
A large local reaction to an insect bite may call for more treatment. Antihistamine or topical corticosteroid can ease itchiness or swelling. So can calamine lotion. A painkiller may help too.
Treatment for severe insect bite allergy symptoms
Adrenaline is the main medication used to counteract anaphylaxis. Your GP will prescribe it in the form of an auto-injector if they think you’re at risk of a severe allergic reaction.
Anaphylaxis can happen fast and it’s important to carry two auto-injectors with you at all times. You may need a second dose to reverse an anaphylactic reaction. Teach family and friends how to use the auto-injector too. Wearing a medical alert bracelet will tell people you may need emergency treatment.
Injectable adrenaline is not a substitute for going to hospital. Always call an ambulance, even if you feel better, in case you have a delayed secondary reaction. Severe allergic reactions need immediate medical attention.
Living with insect bite allergy
Insect bite allergy is relatively rare and severe insect bite allergy even more so. If you’re affected by it, avoiding the bugs that trigger your allergic reactions is one of the most efficient ways to deal with the condition. This, combined with local treatment, can help keep symptoms in check.
