3D Printed Hygiene

The Way Things Were:

“3D prints are not food safe.”

With some caveats and addenda that I’ll get into in a second, this has been the established folk-knowledge of the 3D printing community pretty much ever since its inception, and certainly for as long as I’ve been involved with it (which, admittedly, is not particularly long – I’ve had a printer of some kind for a little over 2 years now, which has had fairly extensive use, especially lately, but I wouldn’t consider myself an expert by any means).

While the actual plastic that makes up 3D printed parts – often PLA (poly-lactic acid, a biopolymer often made from corn starch or sugar cane) or PETG (a variant of polyester) – is actually typically food safe, the main problem that was thought to get in the way is the layer-lines that are found on the outside of 3D printed parts. The thinking was that bacteria would be able to find its way into these tiny openings, and grow there while being unable to be effectively cleaned out. This was the theory put forward by an article published by Prusa3D, who are one of the most prominent makers of 3D printers, when they wrote an article discussing “How to make food-grade 3D printed models.” In short, their conclusion was that without an epoxy surface coating, or other method that fully coats the surface, 3D printed items cannot be made food safe. The link to the article is here: https://blog.prusa3d.com/how-to-make-food-grade-3d-printed-models_40666/

I give all of this information as context because, extrapolating from 3D prints not being food safe, we can also make the fairly easy leap to suggest that 3D prints are not body safe, hence, 3D printed insertables, toys that can break the skin, or other items that could come into contact with mucous membranes are fairly rare, and often come with a fairly large asterisk on their use. Personally, as an example, I have intentionally changed the designs of my 3D printed talons to dull them down and prevent them breaking the skin, as I was concerned about the hygiene implications that would result.

New Research:

In a paper published* in March 2025, Thomas, Amin, Seibi, & Jaafar present the results of their study “Innovations in Sanitization for 3D-Printed Parts in Medical and Critical Applications” which investigated practical ways to bring 3D printed parts, made from PLA and PETG, to a standard of cleaning which is appropriate for food and medical applications. This was motivated by the proliferation of home-brewed PPE which was made during the early days of the COVID pandemic, with many people printing impromptu respirators, ventilator connectors, and more. The paper passed a peer review process in 2025, so I’m fairly confident that it doesn’t have any glaring issues or impossibilities that I’m not seeing, although I do urge people to give it a look themselves.

The paper begins by discussing the issue of lead contamination. Often, the print-head of 3D printers is brass, which contains approximately 1.5% lead. In theory, with brass nozzles, lead could potentially leach out into the printed parts due to corrosion and abrasion on the nozzle. Thomas et al. perform a study using a mass spectrometer on several 3D printed parts, verifying that no significant contamination is present. As an aside, many people (myself included) quickly switch to a steel nozzle to avoid wear on the brass nozzle causing imperfections in prints – the food safety benefits are a bonus.

Next, it examines another issue commonly brought up, which is that the pigments used to colour the plastic filament may not be safe, and could leach out when immersed in fluid. The paper concludes that this is not likely to be a significant concern, as while companies will not usually go to the lengths of acquiring a specific certification on their pigments, they also will avoid using any type of pigment that would require a listing on the filaments material safety datasheet, and so it is highly unlikely to be a dangerous substance. This point is admittedly the most contentious/hand-wavey, but I think it seems overall reasonable to me that the pigments used would be fairly stable in the filament, otherwise printed parts would regularly have their colour fade over time or after washing when I haven't seen that happen much, if at all.

Finally, we reach the most critical part of the paper – actually testing cleaning methods. Using a range of printers and settings, with layers between 0.16 and 0.24mm, they soaked 3D printed parts (a COVID respirator, aiming to provide a complex surface that would prove difficult to clean) in chicken meat residue for 24 hours, to encourage growth of E Coli and Salmonella, two principal hazards for food safety. Afterwards, they swabbed the parts, applied various cleaning methods, and anaylsed the results in a variety of ways, including visual inspection of colony growth on petri dishes, and protein residue testing.

I do encourage people to go and read the study for themselves, as some of the images of the before and after are quite striking, but since I can’t really upload them here I’ll simply verbally report the data! In short, they found that giving uncoated and untreated PLA a simple wash with soapy water was able to achieve a 98% reduction in colony forming units (i.e., the amount of bacteria present which can successfully replicate), compared to 99% reduction when the same treatment was applied to a glass plate, 98% on a metal spoon, and 85% on a plastic cutting board.

The authors then also contacted several hospital technicians to test specimens. They found that after a wash, rinse, and sanitization in bleach water for 2 minutes, they were within specifications safe for food and medical establishments according to the World Health Organization and the Center for Disease Control.

How Does This Affect Me?

In short, not much, since I already wasn’t making toys that were intended to break the skin or come into contact with mucous membranes, but since I’ve recently started making toys that intend to draw blood (albeit using a sterile metal cutting surface), I figured it was worth doing a deep dive on this.

One of the outputs of this paper is a concise cleaning method for 3D printed parts, which I’ll be recommending to people going forward and replicating here. I’ll also be suggesting to people that, while the results of this study are fairly compelling, they are not concrete, and my general advice will be to treat 3D printed toys in a similar fashion to wooden ones – if it gets a person’s blood on it, I’d strongly advise considering it blood bonded to that person going forward.

TL:DR: Cleaning Method

For standard cleaning, especially of items that are not coming into contact with skin or sensitive areas, I recommend a simple clean with warm, soapy water, using a sponge or dishcloth.

One step up, for toys that haven’t been exposed to any particular contaminants or hazards but may be used on them in future, I’d suggest adding a small bit of baking soda (less than a teaspoon) to that dish rag or sponge, and scrubbing with moderate force.

Finally, for parts that have been exposed to bodily fluids or other hazards, I’d suggest mixing up a solution of bleach** and warm water – approximately 1 tablespoon per 4 litres of water – and soaking the part for several minutes, before continuing with other cleaning steps as normal.

I’ll once again state that these steps will not make the item sterile, but will significantly reduce the contamination on the surface. For engaging with needle play or sharps, I’d consider also giving toys a rub with antibacterial hand-gel or wipes before use, even if they’re not directly in contact with the skin.

*Mild addition to note that I didn't quite get this correct; it's a conference paper, meaning that while it has been peer-reviewed to an extent, it has not yet been formally published - I think the conclusions drawn by the paper are still solid, and I think that the steps I/the paper recommend are reasonable when it comes to keeping prints hygienic, but I'll say that I still don't generally recommend sticking uncoated 3D prints inside of bodies on the regular^^

**Based on my knowledge, soaking in bleach will not damage or degrade 3D printed parts, especially not over a short time, but extended immersion (on the order of a week or more) may cause parts to lose some of their colour, and perhaps become somewhat brittle.