Insect repellent, commonly known as bug spray, prevents bites from insects that carry diseases like West Nile virus, Zika, and Lyme disease. These products are regulated pesticides, and their active ingredients are designed to be toxic to insects, meaning they must be used carefully on humans. Understanding the specific chemical risks, concentration limits, and signs of overexposure is necessary to maximize protection while maintaining safety.
Primary Toxic Ingredients and Their Risks
The concentration of active ingredients determines the duration of protection and directly influences the risk of adverse health effects when misused. The most common active ingredient in skin-applied repellents is N,N-Diethyl-meta-toluamide, or DEET. DEET is considered the gold standard for efficacy against a broad range of biting pests. It is a neurotoxin that works by interfering with the central nervous systems of insects.
Another highly effective ingredient is Picaridin (Icaridin), which disrupts the insects’ olfactory senses, making it difficult for them to locate the host. Picaridin has a lower acute toxicity profile than DEET and is less likely to cause skin irritation, making it a popular alternative. Permethrin is sometimes used for clothing and gear; this synthetic pyrethroid insecticide kills insects upon contact but must never be applied directly to human skin. Oil of Lemon Eucalyptus (OLE) is a botanical option that repels insects via scent masking, though it is not recommended for children under three years of age.
Defining Harmful Exposure Levels
Harmful exposure is defined by the ingredient used, its concentration, the frequency of application, and the manner of application. The concentration percentage indicates the duration of protection, not the level of effectiveness. However, higher concentrations carry a greater risk of absorption and systemic toxicity. For DEET, concentrations above 30% offer minimal additional protection time and should be avoided for general use. The American Academy of Pediatrics recommends that repellents used on children contain no more than 30% DEET.
Factors that increase the risk of systemic absorption include applying the repellent over broken, irritated, or sunburnt skin, which allows chemicals to bypass the skin barrier and enter the bloodstream. Excessive reapplication, or using more than is necessary to cover exposed skin, also increases the total absorbed dose. The combination of insect repellent and sunscreen is particularly risky because frequent sunscreen reapplication leads to overexposure to the repellent component. Body weight plays a significant role in toxicity, as smaller individuals, particularly young children, have a higher ratio of skin surface area to body mass, making them more susceptible.
Recognizing Signs of Toxicity and Overexposure
The body’s reaction to overexposure can range from localized irritation to severe systemic poisoning, depending on the chemical and the amount absorbed. Localized symptoms often involve the skin and eyes, where contact can lead to redness, rash, blistering, or a burning sensation. If the repellent is inadvertently rubbed into the eyes, it can cause immediate irritation.
Systemic toxicity, typically associated with excessive or prolonged DEET absorption, affects the central nervous system. Mild systemic signs may include nausea, vomiting, dizziness, or headache, often reported after heavy or frequent use. Severe, acute neurotoxicity, while rare, can manifest rapidly and include slurred speech, mental confusion, and uncoordinated movement (ataxia). The most severe symptoms are seizures and coma. These serious effects are most often linked to misuse, such as accidental ingestion or application over a large portion of the body at high concentrations.
Immediate Action and Safe Handling Practices
Knowing how to apply bug spray safely and what to do in case of an adverse reaction is paramount to prevention and response. For accidental eye contact, immediately flush the eyes thoroughly with clean water for several minutes to wash away the chemical irritant. If severe symptoms of systemic poisoning—such as seizures, confusion, or difficulty breathing—occur, call Poison Control or emergency services immediately.
Preventative application requires using only the amount necessary to lightly coat exposed skin and clothing, avoiding saturation. Never spray repellent directly onto the face; instead, spray a small amount onto your hands and then gently rub it onto the face, carefully avoiding the mouth and eyes. No repellent should be applied to infants younger than two months of age. Avoid applying repellent to the hands of young children entirely, as they frequently put their hands in their mouths. Once the outdoor activity is over, wash the repellent off the skin and clothing with soap and water to minimize prolonged exposure.