the adventures of sock errant
October 27, 2022 5:33 AM Subscribe
According to the label, permethrin-treated clothing is not supposed to be laundered with non-permethrin treated clothing. How concerned should I be about laundering one permethrin-treated sock in a load of non-permethrin clothing?
Details
Details
- one singular InsectShield-treated permethrin sock in a full laundry load
- the sock had not been previously laundered
- most of the other clothing in the load was not of a variety that shouldn't be treated with permethrin
- I rewashed all the other clothing in the washer as soon as I opened the dryer and noticed the errant sock
- both washings were in cold water
- I live in a Lyme-endemic area but most days do not walk on grass or other natural surfaces, so while it's helpful to have permethrin-treated clothing for the occasional hike (which I usually layer over non-permethrin-treated layers to minimize skin contact), there's no reason for me to wear it every day
- I'm a bit anxious about health effects from more permethrin exposure than necessary but am not sure how rational my anxiety is (and know that I'm slightly prone to health worries, though they generally go away once I have better information!). I know permethrin is generally considered to be safe, as described in the linked EPA article, when used in clothing as designed, but am not sure how likely it is for that science to change as further studied as has been the case for some other pesticides
- I'd like to not have to stop wearing the other laundry in that load as clothing shopping is challenging and the load contained a good fraction of my current good clothing, but if there's genuine reason for worry I can manage
We get our kid's entire summer wardrobe and all the adult socks treated by InsectShield and wash everything together. Haven't see any obvious effects, although I suppose there could be some invisible effects such as those we might get from drinking water from plastic bottles. I will say we also didn't find a single tick on us all year and live in a high-Lyme area (including on hikes where other people found ticks). I figured it's just a CYA legal statement, and I'm more scared of ticks than of the permethrin spreading to other clothing in the wash.
posted by epanalepsis at 6:02 AM on October 27, 2022 [1 favorite]
posted by epanalepsis at 6:02 AM on October 27, 2022 [1 favorite]
Solubility in water 5.5 x 10−3 ppm, 0.2 mg/mL (25°C). Makes me thing it washes out by dilution in warm-ish water.
Permethrin - Wikipedia makes it sound pretty harmless except for cats.
One sock in the laundry.... wash it again in at least warm water. How many mg were in that sock? That water solubility and medical use instructions sorta make me not worry about a stray sock in the wash.
posted by zengargoyle at 6:48 AM on October 27, 2022 [1 favorite]
Permethrin - Wikipedia makes it sound pretty harmless except for cats.
Medical useIt might be something to worry about if you have liver problems of some sort,
Permethrin is available for topical use as a cream or lotion. It is indicated for the treatment and prevention in exposed individuals of head lice and treatment of scabies.[11]
For treatment of scabies: Adults and children older than 2 months are instructed to apply the cream to the entire body from head to the soles of the feet. Wash off the cream after 8–14 hours. In general, one treatment is curative.[12]
For treatment of head lice: Apply to hair, scalp, and neck after shampooing. Leave in for 10 minutes and rinse. Avoid contact with eyes.[13]
One sock in the laundry.... wash it again in at least warm water. How many mg were in that sock? That water solubility and medical use instructions sorta make me not worry about a stray sock in the wash.
posted by zengargoyle at 6:48 AM on October 27, 2022 [1 favorite]
I suspect that there may be a different reason for that advice - one of "dilution". To wit:
* If you wash all the treated clothing together, all clothing is shedding permethrin, but it will also be soaking permethrin back up into itself, so the amount of permethrin that is "washed out" of each garment would be minimal.
* But if you wash treated and non-treated stuff together, the permethrin that gets leached out from that treated garment would get soaked up by non-treated ones, so the treated stuff is less treated.
So I suspect the issue isn't that your shirts and jeans and whatever aren't all contaminated - I suspect the issue is more that that one sock now is only 50% as strong as it was, because your shirts and pants and whatever all soaked up a fraction of what had been in that sock.
posted by EmpressCallipygos at 7:33 AM on October 27, 2022
* If you wash all the treated clothing together, all clothing is shedding permethrin, but it will also be soaking permethrin back up into itself, so the amount of permethrin that is "washed out" of each garment would be minimal.
* But if you wash treated and non-treated stuff together, the permethrin that gets leached out from that treated garment would get soaked up by non-treated ones, so the treated stuff is less treated.
So I suspect the issue isn't that your shirts and jeans and whatever aren't all contaminated - I suspect the issue is more that that one sock now is only 50% as strong as it was, because your shirts and pants and whatever all soaked up a fraction of what had been in that sock.
posted by EmpressCallipygos at 7:33 AM on October 27, 2022
The advice not to wash is very conservative. That's fine! Conservative is good, in this context. But don't worry about it is the practical advice. A tiny portion of that "dose" that was on that one sock is now spread across your clothes. Wearing it once will be fine, and what's there will be diluted to basically nothing next time you wash. Permethrin is safe to at a topical dose level to treat scabies or lice; what you're getting is miniscule compared to that.
If you want to be even more conservative, you could just wash the clothes again without the sock. I don't think it's necessary, but it's low effort.
Having dealt with regulators (albeit a different agency) basically what happened is almost certainly: The manufacturer has data permethrin is safe. Someone asks about underwear and long term impact, especially reproductive impact. Manufacturer says they won't put it on underwear. Someone at the agency, earning their money, ask about washing clothes together. Everyone probably thinks it's safe, but there's not a study. So eventually manufacturer asks if they can mitigate risk by saying "don't do this" in the care instructions, and the agency agrees.
This is the sort of thing that agencies don't allow if there is a big risk; they know people will make mistakes. (Obviously there are times regulators fail, but this is such a niche thing I don't think they were under a lot of pressure to enable it.)
I suspect that there may be a different reason for that advice - one of "dilution".
The EPA is quite clear that the advice is to avoid cross-contamination. The is regulatory-mandated advice for safety, non manufacturer advice for efficacy.
posted by mark k at 7:59 AM on October 27, 2022 [2 favorites]
If you want to be even more conservative, you could just wash the clothes again without the sock. I don't think it's necessary, but it's low effort.
Having dealt with regulators (albeit a different agency) basically what happened is almost certainly: The manufacturer has data permethrin is safe. Someone asks about underwear and long term impact, especially reproductive impact. Manufacturer says they won't put it on underwear. Someone at the agency, earning their money, ask about washing clothes together. Everyone probably thinks it's safe, but there's not a study. So eventually manufacturer asks if they can mitigate risk by saying "don't do this" in the care instructions, and the agency agrees.
This is the sort of thing that agencies don't allow if there is a big risk; they know people will make mistakes. (Obviously there are times regulators fail, but this is such a niche thing I don't think they were under a lot of pressure to enable it.)
I suspect that there may be a different reason for that advice - one of "dilution".
The EPA is quite clear that the advice is to avoid cross-contamination. The is regulatory-mandated advice for safety, non manufacturer advice for efficacy.
posted by mark k at 7:59 AM on October 27, 2022 [2 favorites]
I am an entomologist with some expertise in the area of permethrin-treated clothing. The reason for the labelling is not because permethrin is expected to wash out and re-treat clothing as EmpressCallipygos posited above. Permethrin is fairly well bonded to the fabric and very little is lost in each wash. The reason for the warning is health and safety. Safety of some types of clothing items and fabrics has not been determined (not that there is necessarily a risk, just it has not been established one way or the other), and the directions are to reduce the risk of contaminating other clothing articles with permethrin. Pre-treated clothing is only assessed for the safety of that specific pre-treated clothing item and fabric. Permethrin may not bond as well to some types of fabrics, and so be more likely to transfer to skin, which can be a greater exposure risk when dealing with things like underwear, as per the EPA website you linked:
Why the Label Calls for Washing Clothes Separately
Small amounts of permethrin can come off in the wash, as shown by available scientific studies. Only outer clothing is treated with permethrin, as outer clothing is most likely to come into direct contact with the listed pests. Permethrin repellent products used for factory-treatment of clothing or as spray-ons for clothing are not to be applied to certain clothing such as underwear. For this reason, the label instructs consumers to wash permethrin-treated clothing separately from non-treated clothing.
I personally wouldn't worry about washing one pre-treated sock in a load of laundry. Socks are small and very little permethrin comes off in each wash -- InsectShield socks are labelled to provide protection for up to 70 washes, and are expected to provide >95% repellency for that many launderings. This means most of the permethrin is still in the sock, even after 70 launderings, so the amount that could have been transferred from one sock to an entire load of laundry is very small.
posted by fimbulvetr at 8:02 AM on October 27, 2022 [8 favorites]
Why the Label Calls for Washing Clothes Separately
Small amounts of permethrin can come off in the wash, as shown by available scientific studies. Only outer clothing is treated with permethrin, as outer clothing is most likely to come into direct contact with the listed pests. Permethrin repellent products used for factory-treatment of clothing or as spray-ons for clothing are not to be applied to certain clothing such as underwear. For this reason, the label instructs consumers to wash permethrin-treated clothing separately from non-treated clothing.
I personally wouldn't worry about washing one pre-treated sock in a load of laundry. Socks are small and very little permethrin comes off in each wash -- InsectShield socks are labelled to provide protection for up to 70 washes, and are expected to provide >95% repellency for that many launderings. This means most of the permethrin is still in the sock, even after 70 launderings, so the amount that could have been transferred from one sock to an entire load of laundry is very small.
posted by fimbulvetr at 8:02 AM on October 27, 2022 [8 favorites]
Having dealt with regulators (albeit a different agency) basically what happened is almost certainly: The manufacturer has data permethrin is safe. Someone asks about underwear and long term impact, especially reproductive impact. Manufacturer says they won't put it on underwear. Someone at the agency, earning their money, ask about washing clothes together. Everyone probably thinks it's safe, but there's not a study. So eventually manufacturer asks if they can mitigate risk by saying "don't do this" in the care instructions, and the agency agrees.
This is the sort of thing that agencies don't allow if there is a big risk; they know people will make mistakes. (Obviously there are times regulators fail, but this is such a niche thing I don't think they were under a lot of pressure to enable it.)
100% correct, although usually it is the regulator who tells the manufacturer to add the mitigation wording, not the other way around. Regulators are very conservative, especially with domestic products as they can be sold to anyone (as compared to commercial-class products, where there is the expectation that the user has training in pesticide use and will follow the label exactly).
posted by fimbulvetr at 8:06 AM on October 27, 2022 [2 favorites]
This is the sort of thing that agencies don't allow if there is a big risk; they know people will make mistakes. (Obviously there are times regulators fail, but this is such a niche thing I don't think they were under a lot of pressure to enable it.)
100% correct, although usually it is the regulator who tells the manufacturer to add the mitigation wording, not the other way around. Regulators are very conservative, especially with domestic products as they can be sold to anyone (as compared to commercial-class products, where there is the expectation that the user has training in pesticide use and will follow the label exactly).
posted by fimbulvetr at 8:06 AM on October 27, 2022 [2 favorites]
Huh, thanks for asking this. I usually ignore "wash separately" labels since they tend to be about color bleeding. I don't know if I've washed permethrin-treated clothes with the rest of the wash but I'll stop!
posted by potrzebie at 3:33 PM on October 27, 2022
posted by potrzebie at 3:33 PM on October 27, 2022
As zengargoyle notes above, permethrin is used as a topical cream in humans to treat lice and scabies. The FDA considers it safe to put on your skin. The main reason it's not sold as a topical bug repellent is not that it's bad to get on your skin but that it doesn't work well as a topical bug repellent. It's much more effective as a clothing treatment and much safer in general than DEET, which is really the only other bug repellent that's effective.
The big exception of course is if you have cats. It is really bad for cats.
posted by hydropsyche at 6:07 AM on October 28, 2022 [1 favorite]
The big exception of course is if you have cats. It is really bad for cats.
posted by hydropsyche at 6:07 AM on October 28, 2022 [1 favorite]
permethrin is used as a topical cream in humans to treat lice and scabies
Okay, the following is not to cause any fear or concern about the sock (I already said I wouldn't worry about that!), but there is some bad advice about permethrin being stated above.
Do not assume that because one type of product in one type of use scenario is deemed okay, that others are, even with the same active ingredient. There is a reason the CDC says that "Permethrin is safe and effective when used as directed." Those topical treatments are put on to kill lice or scabies and not to repel them (this is an important distinction!), usually only need one treatment, and are rinsed off soon afterwards. As I said above, permethrin is tightly bound to fabrics, which is why it is a good fabric-impregnated insect repellent. Using is as a skin-applied insect repellent would be a bad idea.
Permethrin IS NOT "much safer in general than DEET", and DEET is not the only other bug repellent that is effective (for example, Icaridin/Picaridin works very well, as well as DEET against mosquitoes and lasts longer than DEET against ticks). People often assume DEET is bad for you because it "melts plastic", but that is not an indication of whether or not it is bad for you, it just has a solvent effect on some types of plastics. I used to keep a plastic cup on my desk at work with the imprint of a human hand melted into it to demonstrate this when people brought up DEET and plastic. The imprint was caused by orange peel oil from eating an orange, then touching the glass. I personally prefer to use Icaridin/Picaridin because it doesn't smell like DEET and doesn't damage some plastics. DEET has been in use for almost 80 years (first used in 1946!) with pretty well no adverse human health effects, and as per this quote from Wikipedia:
"this repellent has been subjected to more scientific and toxicologic scrutiny than any other repellent substance. ... DEET has a remarkable safety profile after 40 years of use and nearly 8 billion human applications. Fewer than 50 cases of serious toxic effects have been documented in ... medical literature since 1960 ... Many of these cases of toxic effects involved long-term, heavy, frequent, or whole-body application of DEET. No correlation has been found between the concentration of DEET used and the risk of toxic effects. ... When applied with common sense, DEET-based repellents can be expected to provide a safe as well as a long-lasting repellent effect ... under circumstances in which it is crucial to be protected against arthropod bites that might transmit disease."
One example where permethrin is widely used is on animals (not cats!) to control fleas and ticks, and every year there are many reported adverse effects from those treatments, usually only skin irritation or minor hair loss or skin damage, but sometimes more. Anyways, from Wikipedia on permethrin:
"Permethrin application can cause mild skin irritation and burning. Permethrin has little systemic absorption, and is considered safe for topical use in adults and children over the age of two months. The FDA has assigned it as pregnancy category B. Animal studies have shown no effects on fertility or teratogenicity, but studies in humans have not been performed. The excretion of permethrin in breastmilk is unknown, and it is recommended that breastfeeding be temporarily discontinued during treatment.[13] Skin reactions are uncommon.[22] Excessive exposure to permethrin can cause nausea, headache, muscle weakness, excessive salivation, shortness of breath, and seizures. Worker exposure to the chemical can be monitored by measurement of the urinary metabolites, while severe overdose may be confirmed by measurement of permethrin in serum or blood plasma.[23]
Permethrin does not present any notable genotoxicity or immunotoxicity in humans and farm animals, but is classified by the EPA as a likely human carcinogen when ingested, based on reproducible studies in which mice fed permethrin developed liver and lung tumors.[24]"
posted by fimbulvetr at 7:57 AM on October 28, 2022
Okay, the following is not to cause any fear or concern about the sock (I already said I wouldn't worry about that!), but there is some bad advice about permethrin being stated above.
Do not assume that because one type of product in one type of use scenario is deemed okay, that others are, even with the same active ingredient. There is a reason the CDC says that "Permethrin is safe and effective when used as directed." Those topical treatments are put on to kill lice or scabies and not to repel them (this is an important distinction!), usually only need one treatment, and are rinsed off soon afterwards. As I said above, permethrin is tightly bound to fabrics, which is why it is a good fabric-impregnated insect repellent. Using is as a skin-applied insect repellent would be a bad idea.
Permethrin IS NOT "much safer in general than DEET", and DEET is not the only other bug repellent that is effective (for example, Icaridin/Picaridin works very well, as well as DEET against mosquitoes and lasts longer than DEET against ticks). People often assume DEET is bad for you because it "melts plastic", but that is not an indication of whether or not it is bad for you, it just has a solvent effect on some types of plastics. I used to keep a plastic cup on my desk at work with the imprint of a human hand melted into it to demonstrate this when people brought up DEET and plastic. The imprint was caused by orange peel oil from eating an orange, then touching the glass. I personally prefer to use Icaridin/Picaridin because it doesn't smell like DEET and doesn't damage some plastics. DEET has been in use for almost 80 years (first used in 1946!) with pretty well no adverse human health effects, and as per this quote from Wikipedia:
"this repellent has been subjected to more scientific and toxicologic scrutiny than any other repellent substance. ... DEET has a remarkable safety profile after 40 years of use and nearly 8 billion human applications. Fewer than 50 cases of serious toxic effects have been documented in ... medical literature since 1960 ... Many of these cases of toxic effects involved long-term, heavy, frequent, or whole-body application of DEET. No correlation has been found between the concentration of DEET used and the risk of toxic effects. ... When applied with common sense, DEET-based repellents can be expected to provide a safe as well as a long-lasting repellent effect ... under circumstances in which it is crucial to be protected against arthropod bites that might transmit disease."
One example where permethrin is widely used is on animals (not cats!) to control fleas and ticks, and every year there are many reported adverse effects from those treatments, usually only skin irritation or minor hair loss or skin damage, but sometimes more. Anyways, from Wikipedia on permethrin:
"Permethrin application can cause mild skin irritation and burning. Permethrin has little systemic absorption, and is considered safe for topical use in adults and children over the age of two months. The FDA has assigned it as pregnancy category B. Animal studies have shown no effects on fertility or teratogenicity, but studies in humans have not been performed. The excretion of permethrin in breastmilk is unknown, and it is recommended that breastfeeding be temporarily discontinued during treatment.[13] Skin reactions are uncommon.[22] Excessive exposure to permethrin can cause nausea, headache, muscle weakness, excessive salivation, shortness of breath, and seizures. Worker exposure to the chemical can be monitored by measurement of the urinary metabolites, while severe overdose may be confirmed by measurement of permethrin in serum or blood plasma.[23]
Permethrin does not present any notable genotoxicity or immunotoxicity in humans and farm animals, but is classified by the EPA as a likely human carcinogen when ingested, based on reproducible studies in which mice fed permethrin developed liver and lung tumors.[24]"
posted by fimbulvetr at 7:57 AM on October 28, 2022
Response by poster: Thank you very much to everyone for your perspective! And thank you especially to fimbulvetr for your domain-specific expertise and your commitment to sharing accurate information. And no worries about causing excess worry - the info you share is consistent with what I was previously aware of. (I typically use picaridin spray in addition to the permethrin-treated clothing when needed outdoors, and I'm familiar with the well-tested safety and efficacy of DEET also.)
My general sense with respect to permethrin was that it was generally pretty safe (and safer than acquiring insect-borne illness!) but not quite enough to use without any particular reason (though if I had reason to use it more I would). But if to the best of our knowledge the excess exposure from the occasional accidental laundry mix is negligible in impact, even if it's a first wash (which was much of my concern, since I know e.g. fabric bleed can be more of a concern in a first wash with certain dyes), not going to worry about it :) Thank you again!
posted by beryllium at 2:26 PM on November 2, 2022
My general sense with respect to permethrin was that it was generally pretty safe (and safer than acquiring insect-borne illness!) but not quite enough to use without any particular reason (though if I had reason to use it more I would). But if to the best of our knowledge the excess exposure from the occasional accidental laundry mix is negligible in impact, even if it's a first wash (which was much of my concern, since I know e.g. fabric bleed can be more of a concern in a first wash with certain dyes), not going to worry about it :) Thank you again!
posted by beryllium at 2:26 PM on November 2, 2022
This thread is closed to new comments.
Our 2009 revised exposure and risk assessment evaluated multiple exposure scenarios for permethrin factory-treated clothing, including toddlers wearing or mouthing the clothing, and military personnel who wear permethrin-treated uniforms on a daily basis.
All exposure scenarios showed that permethrin factory-treated clothing is unlikely to pose any significant immediate or long-term hazard to people wearing the clothing.
The amount of permethrin allowed in clothing is very low, and scientific studies indicate that human exposure resulting from wearing permethrin factory-treated clothing also is low.
If you read the whole article there’s a tiny mention of not treating underwear with it, so maybe consider washing underwear a bunch of extra times before wearing it or perhaps discarding depending on your comfort level.
But I think if they’ve decided the chemical is safe for toddlers to chew on, then one sock probably has not done too much damage to your entire load of laundry, which seems reassuring!
posted by nouvelle-personne at 5:53 AM on October 27, 2022 [2 favorites]