Mosquito Bites: Doctor Review of the Most Popular Itch Remedies
I'm on call this sunny June weekend. Here in the Midwestern U.S., school has just finished for the summer, the warmth is rejuvenating after a brutal winter and the days are some of the longest of the year. For me, this translates into the usual calls about sprained ankles, scrapes, bruises and of, course mosquito bites.
Mosquitoes and Their Bites
Mosquitoes seek us out looking for a meal to nourish and hatch eggs. They're not discriminating - man or beast, any source of blood will do. These insects are hatched around water, so environments around wetlands, lakes and even puddles are prime feeding grounds.
Mosquitoes find us by sensing elevations in carbon dioxide which we breathe out. Landing on the skin, they anchor and sink their proboscis into the tissue. As they fill their feeding reservoir with blood, their saliva is released. This saliva is the nasty souvenir that produces the infamous itchy, mounded mosquito bite.
Mosquito bites erupt when the irritating saliva causes a reaction under the skin. The body's defenses release histamines locally from defending white blood cells called mast cells. This happens with varying degrees among individuals yielding different sensitivities and intensities of bites.
Rarely, mosquito bites are more than the simple itchy nuisance that erupts and subsides a few days later. The most notorious complication from mosquito bites is malaria infection. While unheard of in the U.S., it is a major killer on a world scale. Malaria is a parasite that the mosquito transmits into the bloodstream invading red blood cells. Also uncommon, but found in the U.S. is west nile virus. The virus is transmitted into the blood stream and causes insidious neurologic problems. (See my past blog for more information on west nile virus.)
More common than these exotic infections though, is a self-induced complication. Repeated scratching can open the skin leading to cellulitis, an infection of the skin and soft tissue.
Calamine Lotion: As a boy, I got my fair share of mosquito bites. I have memories of hot summer nights laying in bed cooled by the box fan and covered in pink polka dots of dried calamine lotion dabbed over mosquito bites by my mom. Calamine's anti-itch properties are mild and likely due to phenol in the compound. It has also been shown to have some antiseptic properties too and may help prevent infection from scratching. Studies on the efficacy of calamine in relieving mosquito bite itching, however, have not shown benefit. 1
Benadryl Cream: Benadryl (diphenhydramine) cream is marketed also to treat itchy mosquito bites. Unfortunately, antihistamines in a topical form are prone to a phenomenon called tachyphlaxis. By this, the body quickly becomes "used to" the medicine and renders it ineffective. For this reason, I do not recommend Benadryl cream to alleviate itch.
Oral Antihistamines: Oral antihistamines are the mainstay of treatment for mosquito bites. They are readily available over the counter and can take the edge off the itching and selling. The medicines block the body's histamine response to mosquito saliva. On this note, however, it is best if the medicine in the system soon after the bite and ideally before it occurs. While helpful with the itch, they will not shorten the course of the bite. While Benadryl (diphenhydramine) can be sedating, the others (Claritin, Zyrtec and Allegra) are considered non-sedating.
Hydrocortisone: Inflammation on the bite can also be treated with topical steroid cream. This in turn can give some relief in the itch. Lower dose hydrocortisone is available over the counter and more potent creams and ointments are available with prescription. Topical steroids do benefit mosquito bite itch, taking the edge off without shortening the course of the bite.
Home Remedies: Anecdotal evidence exists for counter-distraction efforts to alleviate the itching of mosquito bites. Alcohol or witch hazel give a cooling sensation directing attention away from the itching. The same can also be accomplished using pain. A home remedy accomplishes this by making an "X", pushing the fingernail firmly down on the bit and then rotating to complete the "X".
Mosquito bites are ubiquitous during the summer months and are rarely more serious than being itchy and annoying. While treatment in general aims at making mosquito bites more bearable, important measures can be taken to prevent the bites all together. See my next blog for tips on mosquito bite prevention.
Management of simple insect bites: Where's the evidence? Drug and Therapeutics Bulletin, 2012; 50:45-48.