Insect bites commonly cause mild symptoms of redness, itching, swelling and irritation. A bite may be a small puncture in the skin around which there is redness and itching while a sting is a swelling with a small puncture that consists of the sting which may be visible. The lump may have an inflamed area around it filled with fluid and may be called a weal.

The bites usually resolve in a few hours and may be managed easily at home. However, there are some warning symptoms that need to be watched out for and medical help should be sought if these symptoms are encountered. (1-6)

Allergic reactions to insect bites

Allergic reactions to the bites and stings may be:

• Minor localised reaction

This leads to pain for a few days but resolves with home management. There is patch of redness and a small area of swelling (up to 1 cm) around the bite or sting that goes away in a few hours.

• Large localised reaction

There may be generalized rash, swelling and itching or urticarial. The area around the bite or sting or the entire limb may swell up. The swelling will usually last longer than 48 hours. More bites or stings lead to more severe reactions.

• Generalized or systemic reaction

This is severe form of allergy that leads to anaphylaxis. The patients have usually been bitten or stung once when their body is sensitized to the bite or sting.

Patient is wheezing, breathless, has a rapid pulse rate, rapidly falling blood pressure, nausea, vomiting and diarrhea, swelling of the face, neck and lips and confusion, anxiety or agitation.

General symptoms of insect bites

The general symptoms that occur from insect bites depend on the type of insect.

Symptoms of bites from mosquitoes, ants, midges and gnats

Bites from mosquitoes, ants, midges and gnats lead to small lumps over the skin. These are very itchy since the skin may be allergic to the saliva of the insect that it spreads over the skin before it bites.

Those who are allergic may develop fluid-filled blisters or bullae or circular, fluid-filled areas around the bite (weals) in response to bites from mosquitoes, ants, midges and gnats.

Symptoms of bed bug bites

These are usually mild and lead to minor irritation of the skin. The bits commonly affect the face, neck, arms, legs etc.

Symptoms of flea bites

Flea bites usually occur in small clusters. Those who are allergic to flea bites may develop several itchy lesions called papular urticarial. Blisters or bullae may also form.

Flea bites from pets usually affect below the knees commonly around the ankles. However, forearms may also be affected while holding the pet animal.

Symptoms of bites from horseflies

Horseflies may bite to form a painful weal. Hives, welts or nettle rash may develop as an allergic reaction.

Patient may develop severe allergic reaction as manifested by weakness, dizziness, wheezing, swelling around the eyes and lips called angioedema etc. These bites are bigger than other insects and may get infected and take a long time to heal.

Symptoms of bites from the Blandford fly or black fly

The Blandford fly or black fly is found in East Anglia, Oxfordshire and Dorset. This bites during May and June and may lead to painful lesions in the legs. There may be severe swelling, blisters, pain, joint pain and fever as a reaction to the bite.

Symptoms of tick bites

Ticks (Ixodoidea) are not insects but arachnids. These may leave red lumps where they bite. Allergic individuals may develop itchiness, blisters and bruises.

Ticks may transmit diseases like bacteria Borrelia burgdorferi which causes Lyme disease. In the UK, most common ticks on humans are sheep tick (Ixodes ricinus), and hedgehog tick (Ixodes hexagonus).

Symptoms of mites bites

Mites may bite to leave itchy lumps or blisters. These are common among pet owners. Harvest mites (Tromboculidae) may bite during late summer and usually the larvae of the harvest mite (Neotrombicula autumnalis) attach to the skin under tight-fitting clothes, feed and then detach. This leads to itchy lesions or bullae.

Symptoms of spider bites

Spider bites may also lead to intense pain, swelling and redness. Severe allergic reactions may also be seen with some spider bites.

Wasps, hornets and honeybees stings

This is usually a defence reaction of the insect rather than a bite. The sting causes sharp pain in the area. On the skin there may be a swollen red are with the sting visible on it. The area is painful and itchy.

Bee stings initially feel like wasp or hornet sting. The venom however may spread and lead to an allergic reaction.

Further Reading

• All Insect Bite Content
• Insect bites and stings
• Treatment of insect bites
• Complications of insect bites
• Prevention of insect bites

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.