If you put irritating oil on a tender bit of your anatomy, you may be stuck with the sensation for up to twenty minutes. Hot water, close quarters and abrasion intensify irritants. Hot baths, tight clothing, plastic wrap bondage or broken skin means a much more intense effect if you use a skin irritant. When first experimenting with an irritant, start with a diluted quantity and try it out in the following order, preferably on yourself first. Good items for insertion are cucumbers and Japanese eggplant.
Bad items are rough or abrasive items, or any irritant or potential allergen.
Check for potential allergic reaction before introducing any food to your partner orally or otherwise. Rectal tissue is fragile and it can break, leading to nasty complications, so be sure that anything you insert does not have sharp edges or rough surfaces. If you're playing with ice, remember that ice can break with very sharp edges. Run your ice under warm water to round off edges before you insert it anywhere, and don't use fragile ice structures that may break inside sensitive body parts. Dry ice is not for prolonged contact with skin.