Cast iron cookware has unique benefits. One difference between cast iron and most other cookware is that many people advocate for not cleaning it with any soap between uses, because the soap can degrade the seasoning which protects it. I wonder, how hygienic is that?

The way I understand it, the seasoning on cast iron cookware is a smoothed layer of polymers that prevents food (and bacteria) from contacting and sticking in the iron cookware. Simply scraping it clean, maybe rinsing with some hot water briefly and drying off immediately after, is generally considered enough to 'clean' the cookware.

How is it that bacterial growth on the cookware is never a problem, given they are not washed with soap for long periods of time? I'm under the impression that most kitchenware - pots, pans, dishes, utensils - are susceptible to bacterial growth that could make you sick or transfer illness if you eat with them and don't properly wash off all the food, oils, etc. that gets on them. Does the layer of polymer on cast iron protect it from such growth? The main question here is: Does other cookware really need soap any more or less than cast iron to be used hygienically, and why or why not?

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    $\begingroup$ I assume that during the cooking process, if you're using a cast iron skillet, you typically get it hot enough to kill most pathogens on it! Not sure how that relates to other types of cookware but I cast iron skillets get VERY hot when used. $\endgroup$ – jeanquilt Jul 29 '17 at 16:54
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    $\begingroup$ I think we could argue a negative here. That is, if not washing cast iron cookware was unhealthy, there'd be a lot of sick people :-) $\endgroup$ – jamesqf Jul 29 '17 at 20:00

Soap or detergent does nothing to kill organisms. Instead each detergent molecule has two ends, one being hydrophobic (meaning it's repelled by water) and the other end is hydrophilic (attaching the end to water). When anything is washed with soap or detergent, the oils and dirt on the object - whether it's a dish or your hands - can combine with water as an emulsion and be rinsed away.

Dishes and utensils are only susceptible to bacterial growth if there's traces of food on them. Washing is meant to remove traces of food and oil so bacteria can't multiple on them. The conditions must be right for bacteria to multiple. If traces of food were to be completely dry and hardened on a dish and someone ate off it, the likelihood of any bacteria present on it is close to nil. They need moisture to grow. If dishes had no oily food on them, washing and rinsing with very warm water would be sufficient. I've seen people from other cultures wash dishes with traces of food that are soluble in water. They come out perfectly clean. (As an aside, using a tea towel can often spread bacteria when they're not used properly.) Towels top kitchen contamination hazards list

Bacteria can't multiple in oil. For example, ordinary cooking oil doesn't need to be refrigerated although it can go rancid. A cast iron frying pan is properly meant for frying foods only. No watery sauces should be cooked in them. Even "scraping it clean" shouldn't be done with a sharp metal object as it can remove some of the polymerized hardened oil layer.

I have several cast iron pans that I don't wash. I wipe them out after each use, then I add a little oil nd roughly a teaspoon of salt. With a paper towel, I rub at any bits of stuck on food. If done within a few hours of being used, it effectively removes any food traces, leaving a smooth surface. I usually rinse off the salt in warm water, dry it and then apply a very thin film of oil. I've been cooking in cast iron pans for decades and have never gotten sick or had mild food poisoning (what many people call a 'stomach flu').

Cast iron pans with a layer of proper seasoning and treated like this will definitely not cause sickness. It can't support bacterial growth and as @jeanquilt mentions, the pan gets very hot - enough to blister your skin if you touch them with a bare hand.

  • $\begingroup$ 'Soap or detergent does nothing to kill organisms.' is incorrect - see biology.stackexchange.com/q/39894/1320 $\endgroup$ – Alan Boyd Jul 30 '17 at 10:24
  • $\begingroup$ @Jude can the alkaline pH of soap or detergents not cause any damage to microbes? $\endgroup$ – user 33690 Jul 30 '17 at 14:23

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