Permethrin is a common ingredient in many insect repellent and pest control products. When used as directed, permethrin is generally safe and effective. However, using too much permethrin or using it too frequently can cause potential health risks.
What is permethrin?
Permethrin is a synthetic chemical that belongs to the pyrethroid class of insecticides. It works by attacking the nervous systems of insects, causing paralysis and death.
Permethrin was first registered for use in the United States in 1979. Today it is found in many over-the-counter insect repellent and pest control products designed to repel and kill mosquitoes, ticks, fleas, and other insects. Some common products containing permethrin include:
- Insect repellents
- Lice shampoos and creams
- Pet sprays and collars
- Clothing and gear sprays
- Yard and garden sprays
Permethrin may be listed on product labels under different trademarked names. No matter what it’s called, always check the active ingredients to see if permethrin is included.
How does permethrin work?
Permethrin works by binding to sodium channels on insect nerve cell membranes. This disrupts normal nerve transmission, causing muscle spasms, paralysis, and death in insects.
Permethrin has very low toxicity to mammals, because mammals have different sodium channels than insects. This makes it much safer for human use compared to older insecticides like DDT.
However, some mammals like cats are more sensitive to permethrin than others. Using permethrin products improperly around cats can cause toxicity.
Is permethrin safe when used properly?
Yes, permethrin is generally safe for humans and pets when used according to label instructions. Here are some guidelines for safe permethrin use:
- Carefully read and follow all label directions for proper usage.
- Do not use permethrin products on cats or kittens.
- Use insect repellents sparingly – do not overapply.
- Avoid contact with eyes, nose, mouth and sensitive skin areas.
- Do not spray repellent directly on face – spray on hands first then apply.
- Do not apply to hands of small children.
- Do not use permethrin on lice in children under 2 years old.
- Launder treated clothing before wearing again.
When used correctly at recommended doses, the small amount of permethrin exposure is not harmful. Always be sure to carefully follow all label instructions.
What happens with too much permethrin?
Using too much permethrin or using it too frequently can lead to increased exposure and potential health risks. Here are some possible effects of permethrin overexposure:
Skin irritation
Too much permethrin may cause skin irritation and allergic reactions in some people. Symptoms can include redness, itching, swelling, rash, and burning sensation.
Numbness and tingling
Overexposure to permethrin may cause temporary numbness or tingling in the hands, arms, legs and feet. This occurs as permethrin interacts with nerve cell membranes.
Nausea and headaches
Ingesting or inhaling too much permethrin can trigger headaches, nausea, vomiting and stomach pains in some individuals.
Breathing problems
Inhaling permethrin powder or spray may irritate the lungs and airways, causing coughing, wheezing and shortness of breath in sensitive people.
Dizziness and disorientation
Excessive exposure to permethrin can affect the central nervous system. Symptoms may include dizziness, loss of coordination and balance, and confusion.
Seizures
In rare cases, very high levels of permethrin can overload the central nervous system and trigger seizure activity. This is more likely to occur with ingestion.
Long term risks
The long-term risks of too much permethrin exposure are not fully known. Possible concerns include:
- Hormone disruption – animal studies suggest permethrin may have estrogen-like effects and influence reproductive hormones.
- Neurotoxicity – permethrin may adversely affect development of the child’s brain and nervous system.
- Cancer – permethrin is classified as possibly carcinogenic to humans by the EPA.
- Immune problems – permethrin may suppress the activity of the immune system.
However, more research in humans is needed to fully understand the long-term effects of permethrin overexposure.
Special precautions for infants and children
Extra care should be taken to avoid overusing permethrin products on infants and children:
- Do not use permethrin lice treatment on children under 2 years old.
- Do not apply repellents over large surface areas of children.
- Avoid using tick and mosquito sprays under clothes.
- Spray repellent on your own hands first then apply to child’s face.
- Do not spray product directly on child’s hands – it may get in their eyes or mouth.
Children’s smaller body size makes them more susceptible to potential risks. Be especially careful about proper dosing and usage.
Signs of permethrin poisoning
Seek medical attention right away if you experience any of these signs after using a permethrin product:
- Difficulty breathing
- Swelling of the face, lips or throat
- Dizziness, confusion or disorientation
- Seizures or tremors
- Abdominal pain, nausea and vomiting
- Blistering rash or severe skin reaction
Bring the product container with you to the emergency room. Treatment will depend on the amount consumed and your symptoms.
How is permethrin poisoning treated?
Treatment will vary based on the amount of permethrin absorbed and the symptoms involved. Possible emergency treatments may include:
- Inducing vomiting – if permethrin was recently swallowed.
- Activated charcoal – absorbs remaining permethrin in the stomach.
- IV fluids – to prevent dehydration.
- Anti-seizure medication – to control seizures.
- Epinephrine – to open airways for breathing problems.
- Dermal cleansing – washing skin repeatedly to remove residues.
- Topical creams – to soothe skin reactions.
People with severe poisoning may need to be hospitalized for supportive medical care and monitoring.
How to avoid overexposure
You can avoid problems with too much permethrin by taking these recommended precautions:
- Read labels carefully and follow all usage directions.
- Only use permethrin products as needed.
- Apply thinly and evenly according to label instructions.
- Avoid combining multiple permethrin products.
- Wash treated skin and clothing after use.
- Keep out of reach of children and pets.
- Use extra care when treating children.
- Store in a secure, sealed container.
Carefully following all permethrin label instructions is vital to staying safe and avoiding overexposure.
Conclusion
Permethrin products are generally safe when used properly according to label directions. However, using too much permethrin or using it too often can lead to skin irritation, numbness, nausea, breathing problems, and even seizures in severe cases.
Care should especially be taken when using permethrin on or near infants and children due to risks from overexposure. Seek prompt medical treatment if you experience signs of permethrin poisoning like difficulty breathing, dizziness, or severe rash.
The health risks of permethrin can be avoided by carefully following all label instructions. Using only as directed, washing residues off, and storing securely will help prevent accidental overexposure.