The instruction you’re most likely to meet puts iodine in the same sentence as hydrogen peroxide. When caring for pressure sores: do not use hydrogen peroxide or iodine cleansers unless directed by your provider, as they can damage the skin.
Here is what to use instead. For a stage I sore, wash the area gently with mild soap and water. For a stage II sore, clean the area with salt water, also called saline, and rinse to remove loose, dead tissue.
Iodine shows up in a second place, and it is a different thing. Alongside the over-the-counter cleanser there is a type of dressing. Antimicrobial dressings include iodine-impregnated dressings. These fight a wide range of germs, and they are used for wounds with a surface infection or those with a high risk of infection.
They have limits. These dressings are not for deep wounds, and there is a concern about side effects in the rest of the body with long-term use of iodine-based products.
That difference is the whole answer. An iodine dressing chosen by a clinician for an infected wound, for a set length of time, is not the same as iodine from a bottle used at home as a general antiseptic. The first is a treatment decision. The second is the thing you’re told not to do with a pressure sore.
If you have been given iodine or an iodine dressing to use, that instruction came from someone who examined the wound and comes before this page.