Insect Bites

Symptoms

Three different main courses can be distinguished: 1. A mild, local reaction manifests as burning, pain, itching, redness of the skin, and formation of a large wheal. The symptoms improve within 4-6 hours. 2. in a moderately severe course, there is a more severe local reaction, with symptoms such as reddening of the skin over a larger area and more intense. In addition, there is often significant swelling with pain. The primary cause is thought to be an allergic reaction. Toxic effects may also be involved. The symptoms begin to improve after 2 days, but may persist for a long time, during 7-10 days. However, severe complications are rare. In a systemic reaction (anaphylaxis) allergic symptoms occur, which primarily affect the skin, circulation and respiration. This is based on an allergy of the immediate type, in which IgE antibodies against the insect venom play a role. These symptoms, some of which are dangerous, usually occur within a few minutes:

Finally, a number of possible complications must be considered (see below).

Causes

1. sting by insects of the order Hymenoptera (Hymenoptera): bees usually leave a stinger in the tissue. They sting only for defense (for example, of the hive) and die after the sting. Bumblebees do not die and can sting several times. Wasps and hornets can also sting several times and cause severe allergic reactions. Certain ants also belong to the order Hymenoptera and sting, especially fire ants imported to North America and Australia. When stung, a sterile pustule with subsequent scabbing develops within 24 hours. Insect venom contains a number of protein allergens, many of which have enzymatic activity, e.g. phospholipase A and hyaluronidase. Bee venom differs immunochemically, while individual wasp venoms contain essentially the same antigens. Red fire ant venom is low in protein and contains a mixture of alkaloids. 2. mosquitoes and other insects, see under mosquito bites.

Complications

  • Generalized allergic reaction: anaphylactic shock, bronchospasm, death.
  • Laryngeal edema, choking when stung on tongue or throat.
  • Secondary local and generalized (bacterial) infectious diseases, antibiotics are often prescribed against it. Sepsis is potentially life-threatening (d. there).
  • Transmission of infectious diseases by mosquitoes, e.g. malaria.
  • Abnormal reactions such as nephritis, neuritis, encephalitis or vasculitis.

Diagnosis

Only those who have reacted to an insect bite with systemic reactions should seek medical attention to be tested for insect sting allergy. The diagnosis is made on the basis of the patient’s medical history and a skin test in which small amounts of insect venom are injected into the skin. Insect bites from mosquitoes very rarely cause systemic allergic reactions, but can cause a greater local reaction. Confusion with other skin conditions is possible, including tick bites. Infectious diseases can be transmitted by tick bites.

Prevention

People with an insect bite allergy should avoid situations in which they could be bitten:

  • If insects are nearby, do not move quickly or abruptly. Do not go into the area of the nest.
  • Do not walk barefoot and wear closed shoes.
  • Sweat, breathing (during physical exertion), food, beer, perfumed personal care products and light-colored clothing (eg perfume, skin creams) attract the insects.
  • Do not drink directly from bottles or cans.
  • Wear tight clothing and do not wear wide necklines so that insects do not get caught between clothing and body. Long shirts and pants and gloves (depending on the activity) are recommended.

Many repellents, such as diethyltoluamide, are not effective against bees and wasps. EBAAP is said to be effective. Insecticides, such as wasp sprays, can be used to kill the insects. Specific immunotherapy can be used to desensitize patients with a diagnosed allergy and at risk for general symptoms.For this purpose insect venom is injected under the skin. The treatment is well effective and protects 85-98% of allergy sufferers. The remaining 2-15% experience at least less severe reactions.

Secondary prophylaxis

People with insect sting allergy should carry an allergy emergency kit including epinephrine pre-filled syringe. The adult emergency kit contains two tablets of an antihistamine and two tablets of a glucocorticoid, as well as the epinephrine ready shot.

Nonpharmacologic treatment

Removal of the insect: The insect should be removed as soon as possible to prevent further venom from entering the body. It should not be squeezed with tweezers during this process, as additional venom may be squeezed out. Instead, it is recommended to use a butter knife or a credit card almost parallel to the skin surface to the insect for removal. A tick card or a special suction pump (Aspivenin) is also suitable. Immediate cooling helps against the inflammation, with ice, menthol, ColdHot packs, gel-based externals, cooling plasters or cool compresses.

Drug treatment

If the reaction is mild and localized, good cooling and application of an antipruritic and analgesic gel is sufficient. Medications used include antihistamines, local anesthetics, acetic-tartaric clay solution, essential oils (menthol, camphor), and ammonia solution 10%. Many products are commercially available. Disinfectants can be applied to prevent infection. For a moderately severe course with extensive swelling, internally applied antihistamines, glucocorticoids and analgesics are recommended. They can be supplemented by locally applied agents. According to the literature, no diagnostic test for insect venom allergy and no immunotherapy is necessary in the post-treatment period. In case of a known insect sting allergy, the allergy emergency kit is used in self-medication (see there). Adults take all 4 tablets in the kit. The epinephrine ready shot is used when there are signs of general symptoms as directed by the prescribing physician. Patients should always seek medical treatment, among other reasons, because late reactions can still occur after hours (emergency)!