Substitute for sesame oil (sesame allergy)
Sesame oil has such a distinctive flavour, I'm afraid there's nothing that will give you exactly the same taste. Many sites suggest peanut oil, but this is more or less tasteless in my experience.

I would suggest toasting some unsalted peanuts or cashews and adding them to the stir fry, to get that roasted, slightly smoky flavour. Just add them to a warm, dry pan and toss frequently to prevent burning.

If you're feeling really adventurous you might even try smoking some peanuts (you can do this in a wok with certain wood chips and a bamboo steamer, plenty of instructions online).