QUESTION:

Why do mosquito bites itch?

ANSWER:

            It’s not the bite that itches, but our body’s reaction. The mosquito uses her piercing needle proboscis to penetrate the outer layer of skin. I use “she”, because only female mosquitoes bite. (no sexist jokes please).

            Once the straw-like proboscis gets down through the epidermis, the mosquito searches for a blood vessel in the dermis layer underneath. She secretes a bit of saliva that contains an anti-coagulant that keeps the blood flowing smoothly. She does not want her “soda straw” to clog up. When the blood sucker (no IRS jokes please) is finished with her meal, she flies happily away but leaves behind that saliva.

            Our marvelous immune system senses an invader and produces a histamine to combat the foreign intruder. The histamine gets to the site of the attack and causes the blood vessels to swell. That’s the source of the reddish bump (wheal).

            When the blood vessels expand, nearby nerves are irritated. That irritation is the source of the itching. This entire process takes time, so a person may not realize they’ve been bitten for an hour or two.

            That itching can turn out to be a good thing. It tells us that we have been bitten. Mosquitoes carry some really bad stuff. In the United States it is encephalitis and the  West Nile Virus. In more tropical climates, malaria is the big concern. The itch may be a clue to a potential cause if a person comes down with one of those maladies.

            Some people develop an immunity to mosquito bites and are not affected. On the other end of the spectrum are those that develop swelling of limbs. Benadryl, an antihistamine, is useful, as is Calamine lotion. Ice packs provide relief, same with  aloe, a cream used in many sunburn remedies. 

            Mosquitoes are most active at sunrise and sunset when the air is most calm. Those flying syringes are lightweight creatures and can’t operate when it is windy.

            One of huge obstacles to building the Panama Canal at the beginning of the 1900s was the prevalence of yellow fever and malaria in that tropical climate. The French had lost 22,000 workers in their attempt to build the Canal decades before.

            Colonel William Crawford Gorgas was appointed to solve the problem. Mosquitoes lay their eggs on the surface of standing water. When the larvae hatch, they live just below the water’s surface, breathing through a siphon in their tails. Eliminate the standing water and you eliminate the mosquito. That is just what Colonel Gorgas’s crews did; draining swamps, filling some wetlands, spraying standing pools, fumigating residences, quarantining infected individuals, and providing screened verandas as sleeping quarters. 

            By 1906, one year after the start of the eradication program, only one case of yellow fever was reported and when the construction was finished and the Panama Canal opened, in 1914, there were none.           

Email questions and comments to: lscheckel@charter.net