Wasp stings can cause redness, swelling and itching.
When wasps sting humans, a venom is injected into the skin. This venom usually triggers a localized reaction, which includes redness, swelling and itching at the site of the sting. These minor symptoms are the result of the body's immune response to the venom, according to the University of California Statewide Integrated Pest Management Program.
Bites and Stings
Some insects bite, but bees and wasps sting. When bees sting, they leave behind their stingers with the venom sac attached. They can only sting once, then they die. Wasps, on the other hand, do not die when they sting. They inject venom into the skin by way of their stingers, which remain attached to them. Wasps can sting multiple times.
Reactions
Bee and wasp stings are more likely to cause an allergic reaction than bites from other insects. Severe allergic reactions are rare, and most people only experience localized itching, redness, pain and swelling. These symptoms are the result of the body's immune system launching an attack against the foreign invader--the venom. This response begins with the production of histamines, which are part of the body's natural defense system.
Histamines
Histamines are stored in mast cells and released when a foreign substance is introduced into the body. That foreign substance can include a seasonal allergen, such as pollen, or venom from a wasp or bee sting. The released histamine binds to receptors, causing an increased blood flow to the affected area.
Blood Changes
Blood vessels and capillaries also become enlarged to increase blood flow to the sting site. Fluid is released from the blood to flush the venom from the body. This results in swelling and itching. Simultaneously, cells in the surrounding tissue undergo changes and start to proliferate to form new tissue at the wound site, which also contributes to the itching sensation.
Treatment
Antihistamines such as Benadryl are effective at stopping itching associated with stings. They block the histamine receptors, thereby reducing the bodily reactions that cause the itching. For a localized reaction to a wasp sting, wash the affected area with soap and water. Apply ice to cool the skin. Topical hydrocortisone cream or calamine lotion also will stop the itching. Some people use home remedies, such as a paste of water and baking soda or meat tenderizer.
Tags: swelling itching, affected area, blood flow, body immune, foreign substance, into skin, localized reaction