What is Pyrethrin and Pyrethroid Toxicity?
Pyrethrin and pyrethroid compounds are special kinds of insecticides that come from the Chrysanthemum cinerariaefolium plant. These compounds are safer for humans to use compared to many other insect-killing products used in farming. Natural pyrethrins have been used to kill insects for hundreds of years, especially to control lice and mosquitoes. The first commercially produced pyrethroid, Allethrin, was made in 1953 in Japan and was used to get rid of household pests.
Compared to natural pyrethrins, pyrethroids have several advantages. For instance, they are more dependable in supply as natural pyrethrins have to be extracted from plants, which may have a bad harvesting season. Pyrethroids are also more resistant to breaking down, are stronger in killing insects, and can be cost effectively made on a large scale.
In the late 20th century, more pyrethroid compounds were developed and became popular due to their ability to kill insects in farming, controlling mosquitoes and being safe for general use. Today, about 30% of all insecticides used globally are pyrethroids. These compounds are often used to control pests both in personal and commercial settings. One specific type of pyrethroid, Permethrin, is used in creams to treat scabies and lice.
Pyrethroids, in terms of their structure, mostly contain a substance called a cyclopropane carboxylic acid and a cyclopentenolone alcohol. In the 1970s, it was found that pyrethrins and pyrethroids caused different symptoms in lab rats, depending on the type. Type I caused tremors in rats and was called “T syndrome,” while type II caused movement disorders and excessive salivation in rats, and was called “CS syndrome.”
In the 1980s, new information showed that “CS syndrome” was pretty much always caused by pyrethroids that had a cyano linkage (a special kind of chemical link) at the center of the molecule. “T syndrome”, on the other hand, was almost always caused by pyrethroids that did not have a cyano linkage. Nowadays, type I pyrethroids refer to chemicals without a cyano group, and type II pyrethroids are those with a cyano group. When compared to type I, type II pyrethroids are generally stronger, last longer in the environment, and can be more harmful to humans.
What Causes Pyrethrin and Pyrethroid Toxicity?
There’s not a lot of information available about how most people come into contact with a type of poison called pyrethroids in the United States. The most common ways for people to get exposed are through swallowing it, breathing it in, or having it come into contact with their skin. People who work in agriculture or those who spray large amounts of insecticide are at risk of breathing in or touching pyrethroids.
From 2000 to 2005, the Toxic Exposure Surveillance System (TESS) reported that a third of pyrethroid exposure cases involved children under 6 years old. This suggests that accidental contact with pyrethroids, especially outside of work-related situations, is a significant reason for these poisonings.
Risk Factors and Frequency for Pyrethrin and Pyrethroid Toxicity
Between the years 2000 and 2005, poison control centers in the United States recorded 121,748 cases of exposure to chemicals called pyrethrins and pyrethroids. The annual number of reported exposure cases rose from 13,759 in 2000 to 25,949 in 2005. Notably, about a third of these cases occurred in children under the age of 6. Less than 3% were due to intentional ingestion and the rate of death was less than 0.01%.
In 2022, the National Poison Data System reported 20,123 cases of pyrethrin and pyrethroid exposure. Around 21% of these cases involved children under 6 years old. The number of intentional self-harm cases was similar to past data, accounting for about 2.6% of total exposures. About 17.3% of the people exposed to these chemicals were treated in a healthcare facility, with severe toxicity developing in 0.2% of all cases. Among these cases, four people unfortunately lost their lives, which translates to a case fatality rate of 0.02%.
Signs and Symptoms of Pyrethrin and Pyrethroid Toxicity
When a patient is exposed to certain substances, it’s crucial for healthcare providers to find out how the exposure happened because it can influence how the patient is treated. The most common ways a person can be exposed are through swallowing, breathing it in, or through the skin. It’s also important to know as much as possible about the substance the patient came into contact with.
There are two types of a substance called pyrethroids, and both types can cause symptoms like nausea, vomiting, and shakiness. However, the second type of pyrethroid is more likely to cause symptoms affecting the nervous system, such as tingling sensations, changes in awareness, and seizures. This type also has a higher chance of causing excessive saliva production. Certain chemicals in pyrethroid products might make symptoms last longer or cause their own symptoms. Symptoms usually start just a few minutes to hours after contact with the product, with local irritation symptoms like skin inflammation and stomach pain showing up before whole-body problems like changes in awareness and seizures.
Doctors might notice certain things when examining a patient who has been exposed to pyrethroids. System-wide symptoms such as confusion and changes in awareness can happen, but these are rare and usually only occur when a large amount has been swallowed. They might also see twitching muscles, especially in the arms and legs. If the patient has inhaled the chemical, there might be signs in the lungs when listening with a stethoscope. Patients might also feel stomach pain and tenderness after swallowing the substance. Contact with the skin can cause local irritation and redness. If a patient is allergic to pyrethroids, they might have breathing problems, rashes, low blood pressure, or swelling in their mouth. If the substance has come into contact with the eyes or mouth, expect to see tearing or saliva production.
Testing for Pyrethrin and Pyrethroid Toxicity
Currently, there is no single laboratory test that can identify specific chemicals called pyrethroids in your body. However, doctors sometimes use a technique known as mass spectrometry to detect the breakdown products of these chemicals.
In cases where symptoms might indicate poisoning by another chemical, organophosphates, a test measuring a substance in your blood called cholinesterase might provide additional information. However, these tests aren’t readily accessible and do not always provide a clear-cut yes or no answer. Additionally, they shouldn’t delay the start of your treatment.
If you have been vomiting a lot, your doctor may run a basic metabolic panel. This is a series of blood tests to check your body’s electrolyte balance and make sure you haven’t become dehydrated.
If you show signs of difficulty breathing or fluid buildup in your lungs (pulmonary edema), your doctor may further investigate by ordering a chest X-ray. Some people tend to develop lung complications hours after they have accidentally swallowed certain chemicals. You might want to read this additional StatPearls’ guide about hydrocarbon exposure for more comprehensive information about the evaluation and treatment of such cases.
Treatment Options for Pyrethrin and Pyrethroid Toxicity
If you’re exposed to pyrethrins or pyrethroids, which are types of insecticides, it’s important to seek immediate medical care. Doctors will closely monitor you and provide supportive care to alleviate symptoms and ensure your safety. It’s also common for people exposed to these insecticides to have difficulty identifying the exact product they came into contact with. This situation can be difficult, as there are other insecticides, such as organophosphates, which present overlapping symptoms, including excessive salivation, tears, mental changes, and tremors. However, organophosphates can pose even more serious health risks than pyrethrins. That’s why it’s crucial to get accurate treatment to avoid complications. For example, there have been instances in the past where patients were mistakenly treated for organophosphate poisoning with atropine, leading to severe toxicity and even death.
In case of an insecticide exposure, doctors usually start with decontamination. This step is important not just for the patient’s health but also to prevent healthcare workers from potential exposure. If you show signs of severe reactions, like anaphylaxis, doctors will give you epinephrine, antihistamines, and corticosteroids. These are standard treatments for severe allergic reactions. It’s important to note that some insecticides contain carriers known as hydrocarbons which can cause chemical pneumonia and lead to severe respiratory difficulties, and in some cases, death if ingested. If you have difficulty breathing after exposure, you’ll likely receive oxygen and will be continuously monitored by healthcare professionals. Any skin irritation can be treated by washing the area with soap and water. If you experience strange skin sensations or “pins and needles”, these are often treated with topical vitamin E oil. These discomforting sensations usually disappear on their own within a day.
If you have seizures after the exposure, doctors will typically administer medications like benzodiazepines to help control them. In case you need intubation (a tube inserted into your airway to help you breathe), choosing drugs that act on the GABA receptors in the brain, like benzodiazepines, can help with sedation. If the healthcare team expects persistent seizures, they might monitor the electrical activity in your brain with a test called an electroencephalography. Benzodiazepines can also help calm down tremors, which are another possible symptom of pyrethrin exposure. The time since ingestion plays a crucial role in your treatment. For example, activated charcoal, which helps absorb the poison, may be given if the patient arrives within an hour of ingestion. However, it should not be given if you are vomiting or confused because these increase the risk of aspirating, or inhaling the charcoal into your lungs. Finally, procedures like stomach pumping (gastric lavage) and washing out the intestines (bowel irrigation) are not recommended. A drug called atropine may be considered for excessive salivation or fluid in the lungs but should be used with care due to its potential side effects.
What else can Pyrethrin and Pyrethroid Toxicity be?
Organophosphate poisoning can show symptoms similar to those caused by pyrethrin and pyrethroid poisoning. This should be kept in mind especially if the poisoning is severe. If a patient has tingling sensations (paresthesias) but does not show other symptoms of poisoning, they might be affected by peripheral neuropathies rather than poisoning.
Patients with confusion or seizures should be thoroughly checked for other potential causes including conditions like stroke, metabolic encephalopathy, infections, or other types of poisonings. Should there be signs of required lung inflammation due to a chemical (chemical pneumonitis), it might be due to exposure to many potential products, the most common risk being hydrocarbons.
What to expect with Pyrethrin and Pyrethroid Toxicity
If someone is exposed to pyrethrins or pyrethroids (types of insecticides), they generally have a good chance of getting better because symptoms are usually not severe and will go away with simple care and support. Those who experience skin irritation can expect these symptoms to go away on their own, usually within a day.
However, individuals who have ingested large quantities of these substances may experience more serious body-wide symptoms and might need to be hospitalized. Death is very rare and often only occurs if the person has ingested other toxic substances at the same time.
Possible Complications When Diagnosed with Pyrethrin and Pyrethroid Toxicity
Pyrethrin or pyrethroid toxicity can have a number of complications, such as:
- Seizures
- Nausea and vomiting
- Difficulty breathing
- Trembling
- Changes in mental awareness
- Involuntary movement disorders
- Elevated body temperature
- Skin irritations
- Increased blood sugar level
It is important to notice these symptoms early on and treat them quickly to prevent severe health problems. Medical professionals must stay alert for these symptoms and take care of those affected appropriately.
Preventing Pyrethrin and Pyrethroid Toxicity
If someone has purposefully consumed these hazardous substances, it’s crucial that they receive appropriate medical treatment and be evaluated by a mental health professional. If someone has been accidentally exposed to these chemicals at work or from using bug sprays at home, they should be educated about how to use personal protective equipment properly. This can help them to avoid similar accidents in the future.
