Insect bites such as bites of mosquitoes, fleas, ticks, bugs, beetles, ants, bees, wasps and spiders are common. The effects of these bites, depend upon, the content of pharmacologically active substances in the sting, and the allergic hypersensitivity of the individual to the antigens of the insect.
Pathophysiology of Insect Bites and Their Effect
Stings of bees and wasps contain large amounts of histamine, 5-hydroxytryptamine and kinins which lead to acute pain and an extensive erythematous swelling in the area bitten by the insect.
This swelling develops within a few minutes of the bite and may last for 10 to 12 hours. If the patient is allergic to the sting, he may also have multiple urticarial lesions and develop general symptoms such as fever, headache, fall of blood pressure, shock and death.
Bites of mosquitoes, fleas, ticks, bugs and ants do not contain any significant amounts of pharmacologically active substances and therefore, result in only a transient pain or itching and a minute erythematous papule which may be completely ignored by the patient.
In case, however, the individual is allergic to the antigens introduced during the bite, he is likely to develop severe itching, papules, nodules, papulo-vesicles, vesicles or even urticarial wheals depending upon the nature of hypersensitivity.
The commonest manifestation of allergy to insect bites consists of papular or papulo-vesicular lesions which frequently get secondarily infected with pyogenic organisms.
Treatment of Insect Bites
Patients bitten by bees or wasps should be given an intramuscular injection of an antihistamine and/or antihistamine tablets, twice or thrice a day till the swelling subsides completely.
In case the bites had been multiple and the patient is in shock, 0.5 ml 1 : 1000 adrenaline should be injected subcutaneously to be followed by intravenous fluids as for a patient of shock due to any other cause.
If the patient comes immediately after the bite, the site of the sting should be incised and as much fluid extracted out as possible.
Following this, the local application of a solution of some weak alkali such as sodium carbonate or sodium bicarbonate in the case of bite by a bee and that of a weak acid such as vinegar or the juice of some pickle, or lemon to the bite of a wasp helps in preventing the swellings.
When the patient is allergic to the bites of mosquitoes, ticks, fleas or bugs, he should be treated with local applications of calamine lotion or corticosteroids as frequently as necessary, and antihistamines orally, two or three times a day.
Severe and widespread cases should be treated with oral corticosteroids to obtain quick relief and these should be withdrawn as the patient recovers.
Hypersensitivity generally disappears within a couple of years in most individuals.