Pyrethrin Side Effects

Written by fern fischer
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Pyrethrin Side Effects
( mrmac04, Filiford)

Pyrethrins are one of the "natural" insecticides. They are derived from chrysanthemums, specifically C. Cinerariaefolium and C. cineum. Pyrethrins are used in over-the-counter medications for both humans and animals. Pyrethrins are potent mosquito insecticides used in Africa and areas of the world where mosquito-borne diseases are rampant.


Poisoning from insecticidal pyrethrum use is common. Only the insecticide category of organophosphates has more reported poisonings, as reported to the EPA by poison control centres. Symptoms of acute pyrethrum poisoning are headaches, dizziness and difficulty breathing.

Side effects from use have been reported since the 1920s. They include dizziness, headaches, skin rashes, hives, burning and itching eyes, asthma attacks, respiratory distress and heart failure. These side effects are sometimes classified as allergic reactions.

Pyrethrins are classified as potential carcinogens. Studies in lab animals show increased occurrence of cancer from pyrethrum exposure. Agricultural workers exposed to pyrethrins also have a higher incidence of cancer development.


Products contain natural pyrethrins and/or the more recently developed synthetic versions.

Medications come in gel, shampoo and liquid form. Over-the-counter medications specify wearing rubber gloves when using the products, as well as open ventilation.

Insecticidal pyrethrum is used in the form of dust or liquid spray.


Besides lice and scabies treatments for humans, pyrethrins are key ingredients in many home and garden insecticides and bug-bombs. Bug dust and aerosol droplets are the easiest way for humans to ingest the poison, with severe reactions possible. Pyrethrins are active ingredients in pet shampoos, even though they may be very toxic to cats. Ten weeks after treatment for insect infestations, active residue from pyrethrum was found in carpet dust.

Pyrethrin Side Effects
Pyrethrins are effective against mosquitoes.


The side effects suffered by humans from pyrethrum exposure are magnified in small wildlife. Pyrethrins are toxic to bees and other beneficial insects, fish and aquatic animals, and they have serious neurological effects on small mammals. Pyrethrins cause anaemia in lab animals; they are passed through lactation. Frequent exposure can affect hormones and reproduction.

Piperonyl butoxide, a known carcinogen, increases the potency of pyrethrins, and it is often added to products to improve their performance.


If use is necessary, always follow directions carefully. Never use more than instructed, and do not use more often than recommended. Dispose of unused products and empty containers safely. Always wear a protective mask and protective eyewear and gloves when handling products that contain pyrethrins.

The good news is that the combination of sunlight and air quickly degrades the potency of pyrethrins outdoors. The half-life of pyrethrins in treated soil (the time it takes for half of the chemical to break down into inert molecules) is less than two hours.

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