The short answer
Yes. A little soap won't strip seasoning that has been baked on properly, because seasoning is hardened oil bonded to the iron. What damages cast iron is soaking, the dishwasher and leaving it wet. Wash with a little soap, rinse, dry it over low heat and wipe on a thin layer of oil.
Where the no-soap rule came from
The rule is older than modern dish soap. Soap made at home could carry leftover lye, which is harsh enough to eat into seasoning. Properly made soap today has none left.
Seasoning is oil that has been baked until it bonds to the iron and hardens. A quick wash with soap cleans the surface without lifting that layer.
What actually damages seasoning
Soaking, the dishwasher and leaving the pan wet do far more harm than soap. Standing water starts rust within hours, and a dishwasher cycle can strip a pan back to bare metal.
Steel wool and harsh scouring pads can scratch through thin seasoning too. A new pan, or one you have only just seasoned, is more delicate, so wash it gently for the first few weeks.
How to wash cast iron with soap
Put a small amount of soap on a soft brush, sponge or chainmail scrubber, scrub the pan and rinse with warm water. Dry it straight away over low heat, then wipe on a thin layer of Cast iron conditioner.
This works for every kind of cast iron: skillets, Dutch ovens, griddles and grill pans.
Why we make a soap for cast iron
A mild dish soap will do the job. We make Cast iron pan soap for cooks who want something simpler: a plant-based castile soap from organic sunflower and coconut oils, vegetable glycerin and rosemary extract, with no parabens, phosphates or artificial foaming agents.
It is deliberately unscented, so no fragrance lingers on your pan, and it is made in Montana, USA.
Common questions
Can I use regular dish soap on cast iron?
Yes. A small squirt of mild dish soap is fine on a well-seasoned pan. Rinse it well and dry the pan straight away.
Can I put cast iron in the dishwasher?
No. The long, hot wash strips seasoning and the standing water causes rust. Always wash cast iron by hand.
Do I need to re-season after washing with soap?
No. Dry the pan over low heat and wipe on a thin layer of conditioner. Re-season only if you see dull gray patches or rust.
Can I leave cast iron to soak?
No. Standing water causes rust within hours. Wash, rinse and dry the pan straight away.
