When an insect or arachnid stings, it injects venom, which the body recognizes as a foreign substance. This triggers a response from the immune system, involving the production of specialized proteins known as antibodies. These “sting antibodies” are part of the body’s defense mechanism, designed to neutralize the venom or mark it for destruction. The specific type of antibody produced and the nature of the immune reaction determine whether the response is a normal, localized irritation or a more widespread, potentially severe allergic reaction.
The Body’s General Response to Stings
Upon a typical, non-allergic sting, the body’s immune system defends against injected venom. Immune cells detect these foreign substances, initiating an inflammatory response. This releases chemical mediators, causing localized symptoms such as pain, redness, and swelling at the sting site. This reaction usually subsides within a few hours to a day.
The immune system also produces Immunoglobulin G (IgG) antibodies, which bind to and neutralize venom toxins. These IgG antibodies also contribute to immunological memory, helping the body recognize the venom more quickly if stung again. This normal immune response is generally confined to the sting area.
When the Immune System Overreacts: Sting Allergies
In some individuals, the immune system develops an allergic response to insect venom. This process begins with sensitization, where initial exposure causes the body to produce Immunoglobulin E (IgE) antibodies. These IgE antibodies then attach to mast cells and basophils, priming them.
Upon subsequent exposure, venom binds to these IgE antibodies. This triggers cells to release chemical mediators like histamine, prostaglandins, and leukotrienes. Histamine, for example, increases blood vessel permeability, causing swelling, and constricts airway smooth muscles.
These chemicals can cause allergic symptoms, from large localized reactions to systemic responses. A large local reaction involves significant redness and swelling extending beyond the immediate sting site, sometimes covering an entire limb and lasting up to 10 days. The most severe allergic reaction is anaphylaxis, a life-threatening condition affecting multiple body systems simultaneously. Symptoms of anaphylaxis can include widespread itching, hives, throat or tongue swelling, difficulty breathing, dizziness, rapid pulse, and a sudden drop in blood pressure. This severe reaction can occur within minutes of a sting and requires immediate medical attention.
Identifying and Managing Sting Allergies
Identifying a sting allergy involves a medical history review and diagnostic tests. An allergist inquires about previous sting reactions, including severity and duration. To confirm, a skin prick test places a small amount of insect venom extract on the skin, pricking it to look for a raised, reddish spot within 15 to 20 minutes. If inconclusive, an intradermal skin test injects venom extract under the skin, considered more accurate for detecting IgE antibodies. Blood tests, like a radioallergosorbent test (RAST), also measure specific IgE antibodies to insect venom.
Sting allergy management includes emergency treatment and long-term prevention. Individuals with severe allergies are prescribed an epinephrine auto-injector, which delivers epinephrine (adrenaline) to temporarily counteract anaphylaxis. Administer epinephrine promptly at the first sign of a severe reaction, then seek immediate medical attention, even if symptoms improve, as a second dose may be needed.
For long-term prevention, venom immunotherapy (VIT), or allergy shots, is highly effective. This involves a series of injections with gradually increasing doses of specific insect venom. Over time, this desensitizes the immune system, reducing overreaction to future stings and decreasing severe allergic reaction risk. VIT is effective in 80% to 95% of individuals, typically requiring regular injections for several years for lasting protection.