Forest Pests: Insects, Diseases & Other Damage Agents

Allergic Reactions Hazards of the Outdoors Written by Terry Price, Georgia Forestry Commission Adapted for the web by the Bugwood Network

Venom and saliva of arthropods can cause allergic reactions in humans. The severity of reactions varies and depends on the nature of the venom/saliva and the individual’s sensitivity to it. Most allergic reactions to stings and bites are brought about by the body’s own immune system. Antibodies are produced to attack the intruding allergen. The antibody most closely associated with allergies is immunoglobulin E (IgE). We all possess IgE antibodies as part of our immune systems; however, some individuals appear to produce larger quantities. When these IgE antibodies collide with the allergens, chemical substances are released one of which, is histamine. Histamine can cause a number of reactions in humans. These reactions may affect the circulatory, respiratory and other body systems. The reactions vary in severity depending on the amount of histamine released. Persons whose immune systems are producing large quantities of IgE antibodies will exhibit more intense allergic reactions and are considered to be hypersensitive. Until first exposed to an allergen, the body has not developed any allergenspecific IgE antibodies; therefore, the first exposure to a venom is usually not life threatening. After the body has been exposed to a particular allergen, it becomes sensitized to it and future stings may result in similar reactions or even more severe reactions. The venom of honey bees and certain wasps contains histamine. Therefore, when histamine is injected directly into the body, reactions can occur immediately and are not antibody mediated as described above. Honey bee stings and those of some wasps (social and solitary) contain histamine.

Fortunately only a small percentage of the human population is hypersensitive. The typical response to a single sting is intense pain and burning for 10-15 minutes. A wheal often forms soon after the sting (Figure 1). Some local swelling around the sting site may occur. Generally, after a day or so only an itchy spot remains at the sting site. Non-hypersensitive individuals receiving many stings often experience the same symptoms as with a single sting except the pain and swelling are more intense and last for longer periods. These reactions are referred to as large local reactions but are not considered life threatening and require no medical attention (Figure 2). The reactions of medical concern are referred to as systemic or generalized reactions. Systemic reactions can be classified as cutaneous, vascular, or respiratory. Cutaneous reactions involve only the skin and consist of rashes, itchiness, swellings, hives, and general reddening. Vascular reactions may lead to dizziness, fainting, and unconsciousness. Respiratory reactions consist of swellings and/or massive buildup of fluids in the respiratory system. This causes difficulty in breathing, sneezing, tightness in the throat and chest, or frothing from the mouth. Respiratory reactions are terrifying to the victim because he or she perceives they are suffocating.

Figure 1 - A small welp from a sting of a honey bee Photo by Terry Price, Georgia Forestry Commission Figure 2 - large local reaction to a sting Photo by Terry Price, Georgia Forestry Commission

Other reactions often involve the gastrointestinal tract and result in nausea, vomiting, diarrhea, headache, chills or fever, weakness and a feeling of impending fear. Reactions involving the vascular and respiratory systems are of major medical concern. The inability to obtain air or a very low or absent blood pressure means oxygen deprivation is occurring to the brain that may result in possible death. Reactions, which cause congestion in the heart, brain or lungs, are anaphylactic in nature and are very serious.

Hypersensitive persons can be desensitized by receiving injections of venom preparations from the arthropod species to which they are allergic. The injections are gradually increased in strength until the patient can tolerate a few stings without having an allergic reaction. This procedure is known as immunotherapy and is done by a physician (allergist).

Immunotherapy is a complicated and lengthy procedure and the patient will require numerous injections. The entire program must be completed as prescribed by the physician. Recent studies indicate venom immunotherapy is highly effective in reducing the reoccurrence of a systemic reaction and is recommended for hypersensitive people. However, people who have undergone immunotherapy should continue to avoid stings and be aware that they may be one of the unfortunate few who may react to a sting at some later date. Insect sting kits are available by prescription and come highly recommended for those who are hypersensitive to stings even following immunotherapy. These kits contain a pre-measured dose of epinephrine that can temporarily halt the onset of severe systemic reactions. Sting kits do not replace expert medical care but should be carried by hypersensitive individuals and those who work in remote places far away from emergency medical aid (Figure 3).

Figure 3 - Epipens