Insect Stings and Bites

Basics

A variety of insects sting or bite humans. Stings or bites from bees, yellow jackets, wasps, hornets, ants, spiders, and ticks are common, and are usually harmless. However, allergic reactions to stings or bites can be serious. [Figure 1]. For most people, bug bites or stings are not a major event. They may hurt for a little while and leave a swollen, red mark that eventually goes away. But for about 3% of the population, bug bites or stings can be quite serious -- even fatal. Some people are highly allergic to substances contained in the venom of certain insects — particularly that of bees, wasps, hornets, and fire ants — and may require emergency treatment. Others may acquire infections secondary to insect stings or bites or pick up an infection transmitted by an insect such as a tick.

Figure 1. Brown recluse spider

The brown recluse spider is recognizable for its three pairs of eyes (arranged in a semicircle on its head) and its violin-shaped, dark marking with the neck of the violin pointing towards the abdomen. Adult spiders are usually about ¼ or ½ inch long (10 to 12 mm). You should contact your doctor or health care facility immediately if you think you have been bitten by a brown recluse spider. Fatalities are rare, but the bite is serious and requires treatment by a medical professional. Reactions vary in severity from person to person and depend largely on how much venom was injected at the site. The bite may sting or be painful, and it can also go unnoticed for hours. A small blister usually rises at the bite site surrounded by a large congested and swollen area. Within 24 to 36 hours, you may experience restlessness, fever, chills, nausea, weakness and joint pain.

Causes

After an insect sting or bite, part of the immune system overreacts to substances in an insect’s venom. When the immune system encounters foreign proteins from an insect’s venom (allergens), it releases histamine and other chemicals that cause inflammation of surrounding tissues. Red welts (hives) may show up on the skin. Sometimes deeper tissues are affected. In highly sensitive individuals, this type of allergic reaction can cause a reaction called anaphylactic shock, in which the airways becomes constricted, breathing becomes difficult, and blood pressure drops.

Some ticks harbor infections that can be transmitted to humans [Figure 2]. Ticks survive by feeding on the blood of animals and humans. Some ticks carry organisms that cause illnesses such as Rocky Mountain spotted fever (carried by wood ticks and dog ticks), Lyme disease (carried by deer ticks), ehrlichiosis (rare, often mild with few symptoms, but sometimes severe; carried by deer ticks and Lone Star ticks), and babesiosis (a rare, potentially fatal disease for humans, carried by deer ticks). It usually takes hours or even days of attachment for an infectious agent to be passed from the tick’s saliva to the human bloodstream.

Figure 2. Tick

Some ticks carry organisms that cause illnesses