Have you ever been told the hot, red itchy skin after essential oil application is nothing to worry about? It's just the toxins being excreted from your body? Seriously, this has been told to countless users of essential oils and is not true. We learned in previous lessons how concentrated essential oils are. Remember, they are often 100% more concentrated then the plant from which they were taken. This is your first clue as to why essential oils can cause skin reactions and allergies. But they can also cause other very serious reactions with inhalation or ingestion. Have you ever experienced an adverse reaction to an essential oil? Let's looks at functional groups again. Remember, essential oils are comprised of numerous chemical constituents. These constituents are responsible for the therapeutic actions of the essential oil. But, they're also responsible for adverse reactions such as skin irritation, respiratory irritation, or liver toxicity. Although you won't have to memorize everything about functional groups, I want you to remember some examples of adverse effects related to their chemical properties. Functional groups only predict how an essential oil may act. There are always exceptions, so it is only a generalization. Aromatherapy monographs, reference books, and credible websites will all give you the information you need instead of memorizing everything at this point. Monographs should tell you about any safety considerations of a specific essential oil. You'll learn more about the therapeutic actions of functional groups later in the course. But for now, let's look at possible adverse reactions of the chemical constituents. Generally speaking, phenols are often skin irritants. Aldehydes and sesquiterpenes are skin sensitizers. Some ethers are carcinogenic. And some ketones are neurotoxic. This doesn't necessarily mean these essential oils cannot be used. However, they need to be used with caution for some delivery methods and in smaller doses. We'll look at some specific examples of essential oils that need extra caution in an upcoming lesson. Other factors of adverse reactions can be related to contamination or adulteration of the essential oil. Contamination is the unintentional change often from solvents or plastic components. Adulteration is an intentional change to the essential oil, often adding chemical constituents or synthetics to create more product, thus making it more profitable. Natural chemical constituents are more often the cause of skin irritation than synthetics are. Both contaminants and adulterants are typically detected with the lab analysis such gas chromatography-mass spectrometry which you'll learn more about later this week. Still other factors of adverse reactions may be related to degradation of the essential oil. Some essential oils are very sensitive to degradation which is caused by exposure to light, heat, air, and moisture. Adverse effects of a essential oil also depends on the frequency that an individual uses a specific oil, the concentration of the oil, and many factors of the individual, age, gender, genetic profile, and health status. Now let's test your knowledge on potential adverse reactions to essential oils. It's important to remember that chemical constituents are responsible for the therapeutic effect of and adverse reactions to essential oils. Specific chemical constituents within a functional group of essential oils may be identified as skin irritants, skin sensitizers, neurotoxins, or carcinogens, thus requiring caution with how to administer them. Besides chemical constituents, adulteration, contamination, and improper storage of essential oils may be responsible for adverse effects. This week's discussion is about safety. Share a safety or quality issue you have encountered, or you think will be challenging, or important when implementing aroma therapy in your healthcare practice. Next, let's continue to explore essential oil safety by looking at safety implications related to the skin.