Oils generally come in two kinds: refined and unrefined.
1. Refined Oil: When a peanut or nut oil is refined, the chances of the proteins of that food being in the oil are low. While pure refined peanut oil does exist, it is always safer to avoid peanut oil completely since there is no definitive way to tell how much protein is in that oil.
However, as Dr. Antony Ham Pong states, “if a peanut allergic person accidentally eats a food with refined peanut oil, the chances of having an allergic reaction are low because even there is peanut protein in there, it will likely be in very small amounts.”
2. Unrefined Oil: Peanut and nut oils that are cold-pressed,” “unprocessed,” “expelled,” “extruded”) peanut and nut oils are unsafe for peanut and nut allergic individuals. These are much more likely to contain peanut and nut proteins.
3. Where Peanut Oil is Found: It is also important to remember that peanut and nut oils are found in some cosmetics and body-care products. Pay specific attention to lip balms, lipsticks and lip glosses (some are even peanut-butter-flavored!) since those are coming in direct contact with your mouth.
In restaurants, be sure to ask waiters specifically about the oil used in deep-frying or in sauces; sometimes it is peanut oil.
Sources include: Dr. Antony Ham Pong, allergist