Reactions to mosquito bites are caused by our immune systems response to proteins in mosquito saliva. Similar to how people who have allergies to cats but more localized. Some people – a small portion, can develop significantly large allergic reactions. Most however are local and present with the typical small bump or wheal with surrounding redness and itchiness that firms up over 24-36 hours and resolves on its own over 7-10 days. These typical reactions are annoying, but not dangerous.
Large or severe local reactions -- sometimes referred to as "Skeeter syndrome" -- typically consist of an itchy or even painful area of redness, warmth, swelling, and/or firmness that ranges from 1 inch to more than 5 inches in diameter. Large local reactions develop within hours of the bite and can progress rapidly over 8 to 12 hours or more. Children, adults not previously exposed to the type of mosquito that bit them, and people with immune system disorders, may experience more-severe reactions. In these people, mosquito bites sometimes trigger even systemic symptoms like fevers, general hives, and swollen lymph nodes. Children are more likely to develop a severe reaction than are adults, because many adults have had mosquito bites throughout their lives and become desensitized.
People at increased risk of allergic reactions to mosquito bites of course usually will have a high level of exposure (e.g., frequently outdoors). Infants and young children, newcomers or visitors to a geographic area where there are indigenous mosquitoes that they had not previously encountered, and those people with primary or secondary immunodeficiency may be at higher risk for larger reactions.
The prognosis of large local reactions to mosquito bites are very favorable. Children often continue to develop recurrent large local reactions to mosquito bites for several summers, after which the reactions cease to occur. However, the time to resolution varies.
Diagnosis of large local reactions to mosquito bites is based on the time of onset (hours) of the reaction in relationship to a witnessed or likely mosquito bite and on the physical finding of an itchy, red, warm swollen area at the site of the bite.
A large local reaction to a mosquito bite can appear like a bacterial cellulitis or skin infection and large local reactions can look like other insect bites and stings. The key information needed to distinguish a large local reaction to a mosquito bite from cellulitis or skin infection is the time between a witnessed mosquito bite (or exposure to mosquitoes and a likely mosquito bite) and the appearance of an itchy, red, swollen area at the bite site. This interval is typically minutes to hours with large local reactions and days with cellulitis. Mosquito bites are generally painless, compared to the bites from flies and other insects and painful stings from bees, wasps or fire ants that can cause large local reactions.
To avoid mosquito bites measures might include staying indoors at dawn and dusk and avoidance of wetlands. Any standing water should be eliminated around the home like standing water in gutters, wadding pools, fire pits or pots of plants in order to reduce breeding areas for mosquitoes. Empty standing water at least once a week from birdbaths. Any water that stands for several days can be a breading spot for mosquitos.
Screens on windows and doors should be well maintained – repair holes and tears that may allow the mosquito in your environment. Consider using mosquito netting over strollers and cribs or when sleeping outdoors.
Over the Counter Insecticides and Repellants
The most effective insecticides and repellents in the United States include:
- Icaridin (also called picaridin)
- Oil of lemon eucalyptus (a plant-based compound)
The insecticide permethrin is suitable for application to fabrics (for example, camp tents, sleeping bags, and clothing), but not for direct application to human skin. Permethrin-impregnated clothes (e.g., shirts) are available commercially. Permethrin is great for tick protection as well.
Different insect repellents are available in a variety of formulations and concentrations. The most effective repellents are DEET (N,N-diethyl-3-methylbenzamide) and picaridin.
We attract mosquitoes by our body odor, skin temperature, and exhaled carbon dioxide. DEET-containing products provide excellent protection against bites. The higher the DEET concentration, the longer lasting the protection. DEET in a concentration of 10 percent can be applied safely to the skin of children over two months of age. DEET is potentially neurotoxic if applied in high concentrations to open skin wounds or sunburned skin or if unintentionally ingested or inhaled. Carful placing DEET on things such as mosquito nets, spandex, rayon, leather, and plastic eyeglass frames and watches --- DEET can dissolve these items.
Picaridin forms a barrier around us and blocks insects' ability to locate human skin. It is odorless and has lasts for about 8 to 10 hours. It is more effective and safer than DEET. Picaridin can be applied safely to the skin of children over two months of age.
Other agents, such as citronella and lemon eucalyptus oil, are less effective and relatively short acting. For example, citronella may be effective for only 20 minutes, and eucalyptus oil may be effective for only couple of hours.
Follow label recommendations and instruction for any of these products.
Studies do support pre treatment of mosquito exposure with oral non-sedating anti-histamine, such as Zyrtec (certirizine), Claritin (loratadine), or Allegra (fexofenadine). This relieved itching in the early-phase allergic reaction and reduced the late-phase reaction (redness, swelling, and induration/firmness). For those with a history of severe or large reactions (Skeeter Syndrome) I’d suggest that a non-sedating antihistamine be taken on a regular daily basis when mosquito exposure is inevitable and that such antihistamines should also be used to treat itching, redness, and swelling that occur at mosquito bite sites. Of course check with your doctor before taking medication --- a physician should supervise its effects.
Remedies to Relieve the Bite
To relieve itching, redness, warmth, and swelling, you can try putting calamine lotion or hydrocortisone cream on the bite. You can also try dabbing a paste mixture of baking soda and water. Most mosquito bites stop itching and heal on their own in a few days. Applying a cool compress for a few minutes can help well. And for stronger reactions, try taking a non-prescription anti-histamine (listed above) may be effective as well.
Antibiotic treatment is not indicated for large local reactions that develop within hours of mosquito bites, because it is unlikely that bacterial infection would develop this rapidly. But if the reaction occurs days after initial bite then be seen by your doctor for assessment and possible need for antibiotics.
Repellant Quick Do’s and Don’ts
If you're also using sunscreen, put it on first, about 20 minutes before applying the repellent.
Avoid products that combine sunscreen and repellent, because you'll likely need to reapply sunscreen more often than repellent. And it's better to use only as much repellent as you need.
Used according to package directions, these products are generally safe for children and adults, with a few exceptions:
- Don't use DEET-containing products on infants younger than 2 months.
- Don't let young children get DEET or picaridin-containing products on their hands or faces.
- Don't use oil of lemon eucalyptus on children under age 3 years.
- Don't apply repellent under clothing.
- Don't apply repellent over sunburns, cuts, wounds or rashes.
- When you go indoors, wash with soap and water to remove any remaining repellent.
I hope this helps as we transition into the breeding season. Even as repellant makers and officials find new ways to prevent or treat them, mosquito-borne diseases aren’t going away. But taking the proper precautions, and staying informed, will always be the best ways to avoid getting seriously sick from these bloodsuckers.
This information is provided by Dr. John E. Thomas with On Point Primary Care clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your primary care provider for advice about a specific medical condition. Feel free to contact Dr. Thomas at firstname.lastname@example.org if you have questions or would like further information about his practice or to schedule your free consultation to see if On Point Primary Care is right for you and your family.