DIY Infused Olive Oils. Read up on safety first. Commenter wrote: Please be careful with your oils. Botulism can grow where any water is present. Garlic (more common) lemon peel, and any fresh herbs are at risk. To avoid any chance, refrigerate and use within a week. Other methods are using dried OR preserved herbs/garlic (vinegar or brine) and just adding oil (or heating oil) together.