Insect Repellent

Aka: Insect Repellent, Mosquito Repellent, Diethyltoluamide, DEET, Citronella Oil, Picaridin

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II. Epidemiology

  1. DEET used by 200 Million persons worldwide
  2. Used by 38% of U.S. population
  3. Only 30 adverse events reported between 1966-1997

III. Indications

  1. Prevention of Vector-borne Infection in endemic areas
  2. Prevention of Insect Bite

IV. Mechanism

  1. DEET concentration above 10% lasts longer, not better
  2. Insect Repellents work as a chemical barrier
    1. Block Mosquito's detection of prey

V. Adverse Effects (DEET)

  1. General
    1. Concentration >15% associated with adverse effects
    2. Most DEET preparations safe
  2. Local Effects
    1. Mild skin irritation
    2. Corneal irritation
    3. Mucosal irritation
  3. Serious effects with excessive use under Occlusion
    1. Neurologic
      1. CNS Depression
      2. Seizures
    2. Cardiovascular
      1. Hypotension
      2. Tachycardia
  4. Other effects: Gastrointestinal
    1. Nausea and Vomiting with ingestion

VI. Efficacy

  1. DEET is effective against Mosquitoes, ticks, lice, fleas

VII. Technique

  1. Apply every 1-2 hours during exposure
  2. Apply Sunscreen before (under) Insect Repellent
  3. Do not apply repellent around eyes and mouth
  4. Concentration up to 30% may be used in pregnancy and over age 2 months

VIII. Preparations

  1. DEET concentration affects duration of activity, not the effectiveness
    1. Duration 2 hours: 6% DEET
    2. Duration 2-3 hours: 10% DEET
    3. Duration 3-5 hours: 20% DEET
    4. Duration 5-6 hours: 30% DEET
    5. DEET concentration above 50% offers no benefit over lower concentration, but raise toxicity risk
  2. Longest acting and most effective agents
    1. Ultrathon (34% DEET): 12 hour protection claimed
    2. Deep Woods Off (23% DEET): 200-360 minutes protection
    3. Sawyer Controlled Release (20% DEET): 180-325 minutes
      1. Slowly releases DEET in response to sweating
      2. Lower toxicity due to slow release
    4. Off Skintastic (6.6% DEET): 90-170 minutes protection
  3. Moderate duration of activity and effectiveness
    1. Avoid combined Insect Repellent with Sunscreen (Sunscreen needs more frequent application)
    2. Bite Blocker Kids (2% Soybean oil): 16-195 minutes
    3. Off Kids Skintastic (4.75% DEET): 45-120 minutes
    4. Skin-So-Soft Bug Guard Plus (7.5% IR3535): 10-60 min
  4. Shortest duration and minimal activity (<5 to 20 minutes)
    1. Citronella (avoid; 10% lasts 20 minutes)
      1. Natrapel
      2. Herbal Armor
      3. Green Ban for People
      4. Buzz Away
      5. Skin-So-Soft Bug Guard
      6. Skin-So-Soft Moisturizing Suncare
    2. Wrist Bands (ineffective, avoid)
      1. Gone Original Wristband (9.5% DEET)
      2. Repello Wristband (9.5% DEET)
      3. Gone Plus Repelling Wristband (Citronella)
  5. Alternatives to DEET with similar efficacy to DEET 10 to 15%
    1. Nootkatone (sesquiterpenoid)
      1. Pending release in 2022
    2. Insect Repellent 3535 (Ethyl butylacetylaminopropionate)
    3. Picaridin 7 to 10% (e.g. Cutter Advanced, Natrapel)
      1. Less irritation and better smell and feel than DEET
      2. Duration of effect is 2 hours
      3. Safe in pregnancy and children down to 2 months of age (at concentration 10% or less)
    4. Lemon Eucalyptus Oil 30% (e.g. Repel Plant Based)
      1. Active ingredient is para-menthane-3,8-diol
      2. Do not use in children under age 3 years (not studied)
      3. Appears as effective as 15% DEET for Mosquito protection, but unclear if it protects against ticks

IX. Precautions

  1. Limit DEET concentration to less than 30 to 35%
  2. CDC recommends DEET 35% for Malaria prevention
  3. Avoid supplements (e.g. B Vitamins, Garlic) for Insect Bite protection (ineffective)

X. Management of toxicity

  1. Skin Decontamination
  2. Seizure management with Benzodiazepines
  3. Supportive management

XI. References

  1. (2022) Presc Lett 29(6): 31-2
  2. (2005) Presc Lett, p. 36
  3. Fradin (1998) Ann Intern Med 128(11):931-40 [PubMed]
  4. Fradin (2002) N Engl J Med 347:13-8 [PubMed]

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