There are few essential that can be applied to the skin undiluted - Chamomile, tea tree and Lavender are the most common. Care is still needed - avoid sensitive areas and use only a few drops at a time.
Undiluted essential oils may be sprinkled lightly on household surfaces, and bedsheets, applied to cotton balls and swabs. To use as a perfume A few drops of essential oil may be dabbed on shirt collars, and at the pulse points. Remember less is more - always carefully test skin for sensitivity.