What Can I Do About All These Mosquito Bites?

Patient Presentation
A 6-year-old female came to the office with mosquito bites that her mother was worried were infected.
The child was outside in the early evening two days ago and was bitten several times on her legs, arms and face. Since then she has been very itchy and has scratched the bites.
She has taken some diphenhydramine with some decrease in itching, but her mother noted that three of the bites on her lower legs look larger, redder and have a yellow discharge on top of the scratches since this morning.
The past medical history showed that the girl had an exaggerated response to mosquito bites with large wheal reactions locally. She has not had allergic-type responses to other insects, bees or wasps according to her mother.
She usually responds well to diphenhydramine.
The pertinent physical exam showed a healthy female with no fever and obvious insect bites in the noted locations.
They had been scratched and two lesions on the right leg and one on the left had 1-1.5 cm raised, red circular lesions with a diffuse border. The center had a yellowish discharge.
She had no lymphatic streaking coming from the lesions. The rest of her physical examination was normal.
The diagnosis of insect bites with secondary impetigo was made. She was begun on mupirocin ointment for the impetigo and hydroxyzine for the itching. She and her mother were told to return to clinic if any fever, increased swelling or streaking of the lesions occurred.
They were also instructed on using insect repellents with less than 10% DEET in them and how use them properly. They were also instructed to wear long-sleeved clothing and to avoid early morning and early evening times outside.

Impetigo is a common infection and is often caused by Group A Streptococcus including Streptococcus progenies. It can also be caused by Staphylococcus auras.
It occurs at the site of skin breaks such as insect bites or other wounds, and is highly contagious. In healthy children and adults it can usually be treated with topical mupirocin which also may be helpful in limiting person-to-person spread.
Oral treatment is good when there are multiple lesions in dispersed places on a single individual, or multiple family members, child care groups, or athletic teams where several individuals are affected.

Learning Point
Mosquitos go through four life stages – eggs which hatch when exposed to water, larvae which live in the water, pupa which occurs just before becoming an adult, and adult which emerges from the pupa and flies out of the water.
The adult then feeds on mammals including humans. Many diseases are transmitted by mosquitos including Yellow Fever, Malaria, Dengue Fever, West Nile virus and many others.

Insect repellent with active ingredients which have been registered with the Environmental Protection Agency (EPA) have been evaluated for effectiveness and potential side effects to humans and the environment.
Those approved are not expected to cause unreasonable adverse effects when used according to label instructions.

Two active ingredients with a higher-degree of efficacy and longer-lasting protection are DEET (N,N-diethyl-m-toluamide) and Picaridin (KBR 3023).
Oil of Lemon Eucalyptus (p-methane 3,8-diol [PMD]) which is a plant based repellent, is found to have similar protection to low concentrations of DEET, but it is not labeled for children under 3 years of age.
Permethrin is also a registered active ingredient commonly used on clothing, shoes, and camping gear. It retains its effects even after repeated laundering. Permethrin should not be used directly on the skin.

General recommendations for repellents include:

  • Repellents should be applied before going outside even for brief time periods.
  • Repellents should be used on clothing as much as possible with the lowest concentration that is effective for the conditions. More than 50% DEET does not offer additional protection.

    For children, the highest concentration recommended is ~10% DEET.

  • Repellents should be used on (not under) clothing and on intact skin (never on cuts, wounds, irritated skin or mucus membranes). It should not be applied to children’s hands as they put them in their mouths.
  • Spray repellents should be sprayed onto hands and applied to appropriate skin areas. It should never be sprayed directly toward the face. Hands should be washed after applying the repellent. Children should not apply it themselves. An adult should do this for them.
  • A thin film of repellent is generally enough. Saturation is not required. A second thin film can be applied again if biting continues.
  • Reapply the repellent after several hours (>3-4 hours or less depending on the label instructions) and after water exposure (i.e. swimming, sweating, etc.).
  • Wash skin with soap and water after coming inside. Launder clothing also. This is important so the repellent does not build up.
  • Separate sunscreen may be used with DEET products when used according to the instructions. No data is currently available regarding the use of other active ingredients in combinations with separate sunscreen.

The EPA does not recommend other precautions for using registered repellents on pregnant or lactating women or for children.
The American Academy of Pediatrics states “Insect repellents containing DEET with a concentration of 10% appear to be as safe as products with a concentration of 30% when used according to the directions on the product labels.” The AAP also recommends not using DEET until older than 2 months of age.
The AAP does not have a recommendation for Picardy or Oil of Lemon Eucalyptus use.

Other recommendations include:

  • Keep the repellents out of children’s reach.
  • Wear clothing that covers as much of the body as possible. Use permethrin repellents on clothing only (and not on skin).
  • Use mosquito netting over the top of infants in carriers, strollers, etc.
  • Don’t let water stand around such as kiddie wading pools, buckets, bird baths, drainage ditches, etc. These represent a mosquito breeding area and also a drowning risk for children.
  • Contact the local government regarding other environmental controls for swamps, marshes, ponds, lakes, etc.

Questions for Further Discussion
1. What are the symptoms of West Nile Virus?
2. What other insects do mosquito repellents also repel?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MEDLINEplus for this topic: Insect Bites and Stings
and at Common Questions, Quick Answers for this topic: Mosquito Bites

To view current news articles on this topic check Google News.

American Academy of Pediatrics. Group A Streptococcal Infections In Pickering LD, Ed. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th edit. Elk Grove Village, IL: American Academy of Pediatrics; 2003;573-584.

American Academy of Pediatrics, Committee on Environmental Health. Follow Safety Precautions When Using DEET on Children.
AAP News, June 2003. Available from the Internet at: http://www.aap.org/family/wnv-jun03.ht.

Centers for Disease Control. Mosquito-borne Diseases. Available from the Internet at:
http://www.cdc.gov/ncidod/diseases/list_mosquitoborne.htm, (rev. 4/23/2004, cited 5/22/06)

Centers for Disease Control. What you Need to Know About Mosquito Repellent. Available from the Internet at: http://www.cdc.gov/ncidod/dvbid/westnile/mosquitorepellent.htm (cited 8/5/05,cited 5/22/06)

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effecively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.

    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    12. Evidence from scientific studies related to the patients’ health problems is located, appraised and assimilated.
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

    Donna M. D’Alessandro, MD
    Associate Professor of Pediatrics, Children’s Hospital of Iowa

    June 5, 2006