Essential oils are safe if used in the right amount (either in diluted form or with carrier oils). It's also important to note that essential oils used as fragrances are generally considered safe, although some people may have sensitivities to certain ones. It's hard to predict which ones would cause this for you; that's why a patch test is important. In general, citrus oils like lemon, lime, tangerine, grapefruit, mandarin, and bergamot should not be applied to sensitive skin and scalp types. Other oils to avoid are camphor oil and mint oils such as peppermint, wintergreen, pennyroyal, and balm mint.