Dilution for topical use: Many oils should be diluted with a carrier oil prior to application. A carrier oil will not dilute the effects of an oil but will reduce the risk of skin irritation and prevent waste.
Photosensitivity: Some essential oils (like citrus oils) are considered photosensitive due to the potential reaction with sunlight. You should spot test an oil to see how/if your body reacts. In addition, YL recommends avoiding sunlight for 12-24 hours following topical application of photosensitive oils (labels will have a warning).
Read the label: each bottle will have information on how the particular oil can be used - aromatically, topically, and/or ingestion. Every oil's use will be different and not all oils are recommended for all types of use, so be sure to read the label!
Using essential oils while pregnant or nursing: it is always recommended to consult your physician for more information prior to use. Personally, I have used oils during pregnancy and have many friends that continued their use of oils during pregnancy and nursing. I avoid oils containing camphor and YL suggests avoiding Clary Sage, Sage, Tansy, Hyssop, Fennel, and Wintergreen (including blends and supplements which contain these).
Using essential oils on children: again, it is always recommended to consult your physician for more information prior to use. The most important thing to remember is DILUTE, DILUTE, DILUTE! Use caution on children under the age of 2. YoungLiving actually has a line of pre-diluted oils called KidScents.
Using essential oils on animals: consult your vet for safety information prior to use. The key with animals is observation as they cannot tell us when they are uncomfortable. When used properly, eo's can provide support for allergies, anxiety, paws, ears, skin, coat, joint and muscles. The "no" list for dogs includes but is not limited to: Cinnamon, Citrus, Peppermint, Pine, Tea tree, Wintergreen, Ylang ylang, Clove, Thyme and Juniper. The "no" list for cats includes but is not limited to: Wintergreen, Citrus, Pine, Ylang ylang, Peppermint, Cinnamon, Clove, Eucalyptus, Tea tree, Thyme, Oregano, and Lavender. YoungLiving has a line of pre-diluted products called AnimalScents.