Insect bites normally cause pain and swelling. This is due to the effect of the venom. The degree of reaction produced depends upon the type and quantity of venom introduced. But in some people the venom acts as an antigen and, with the antibodies already present, causes an allergic reaction.
In relation to the allergic reactions produced, the insects may be divided into two groups—the stinging insects and the biting insects.
BITING-INSECT ALLERGY
Allergic reaction to biting insects such as mosquitoes, sandfly etc., is not immediate; it is a delayed one. After several hours of the bite, there appears redness and swelling around the site bitten. There may be some rise in temperature of the body. However, the reaction is never serious, never fatal.
This reaction needs no treatment, except occasionally a tablet of antihistamine to check itching. As the season advances, after many such bites, the body reacts less to them. That is also the reason why these reactions are more severe in children than adults or older people.
STINGING-INSECT ALLERGY
Stinging insects such as bee, wasp and hornet produce an immediate allergic reaction. This may vary from local redness and swelling to the redness of the whole part, or even generalized swelling, urticaria, choking, difficulty in breathing, unconsciousness and death.
Those who have hay fever, eczema, asthma and drug reaction are more liable to get different grades of severe reactions to stinging insects. Establishing diagnosis is easy from the history of the patient.
The best prophylaxis is to avoid situation where one can be stung by the insects and keep the body well covered while going outdoors in the fields and gardens. As soon as a person is stung, he should try to remove the sting from the site with a pin or needle without rubbing it in.
If the sting is on a limb, tie a tournique—an applicance for compressing the blood vessels—tightly just above the site of the sting. This would avoid spread of the venom in the whole body. Loosen the tourniquet a bit every five minutes or so and then remove it after half an hour or so. If possible and available, apply an ice-pack to the area of sting. Take an antihistamine tablet.
If the past experience indicates severe reactions to the stings, it is essential for the person to keep a syringe and an ampoule of adrenaline with him and inject lA to 1 ml of it subcutaneously in the outer side of the thigh, and then report to the nearest doctor or dispensary.
Hyposensitization against the sting venoms of different insects is practised now-a-days with very good results. Besides insect bites, another type of hypersensitivity to insects discovered lately is the one related to their remnants. Insects have a very short life span and when they die, their bodies, wings, etc., disintegrate and become part of the dust.
During the monsoon, millions of insects appear for a day and die. It has been discovered that some people become allergic to the remnants of the insects and when exposed to such a dust, experience allergic symptoms appear only in a particular season. Previously such cases were thought to be allergic to a certain pollen appearing in that these grave negative reactions, it was thought that either the relevant pollen had been omitted from the pollen calendar or that they were allergic to something else in the atmosphere in that particular season.
Further research revealed that these patients were allergic to the insects present in that season. Some patients are allergic to insects that are perennial and hence they have their symptoms throughout the year.
Patients allergic to insects may be allergic to pollens, moulds and dusts as well. Hence, while being treated they have to be hyposensitized against all the offending allergens so as to get maximum benefit.
Just as a calendar is prepared for the pollens and fungi, so also is a calendar made for insects and correlated with the symptoms of the patient in a particular season.