Essential oils have become increasingly popular over the past few years as people use them to manage issues including stress, anxiety, headaches and muscle pain, and even the common cold. They’re most commonly applied topically or used with a diffuser — but some have even suggested ingesting essential oils. It probably won’t surprise you that experts strongly advise against taking them orally, but that doesn’t mean there aren’t any risks associated with topical application and diffusers. If you use essential oils or are considering giving them a try, here’s what doctors want you to know about how to do so safely.

What Is the Safest Way to Use Essential Oils?

“People often equate ‘natural’ with ‘safe,’ but unfortunately, this isn’t always the case. Essential oils are made of chemicals, just like everything else,” Samantha Radford, PhD, an exposure scientist and owner of Evidence-Based Mommy, told POPSUGAR. She explained that essential oils are extremely potent — for example, it takes three pounds of lavender flowers to make one teaspoon of oil — and because of this, the safest way to use them is with a diffuser. Still, you should be aware of the risks associated with them. “Many oils, such as eucalyptus and rosemary, are not safe for children,” Dr. Radford said. “Others aren’t safe for those with heart problems.”

Aromatherapy humidifiers are also generally safe when used properly. Both Dr. Radford and Tina Gupta, MD, an ACE-certified fitness nutrition specialist and owner of The Lifestyle Cure, explained you can safely use an aromatherapy humidifier for up to 30 minutes at a time, three times a day. “The reason this timeline is considered to be safe is because overuse has been associated with the development of headaches,” Dr. Gupta said. “And use of aromatherapy for upwards to an hour has resulted in elevations in blood pressure and heart rate.” However, these times can vary depending on the person, she added — so it’s important to speak with your doctor if you have any health concerns.

Dr. Gupta told POPSUGAR that topical methods can also work well. However, there are a few important things to remember before applying essential oils to your skin. Dr. Gupta cautioned to keep them away from your eyes, ears, and mouth. “They shouldn’t be applied over broken, irritated, or damaged skin,” she said. Dr. Gupta also recommends doing a patch test — apply the oil to a small area of your skin and wait 24 hours to see if there’s any redness or irritation. “Never use an essential oil if applying it to the skin for more than six months, especially without an antioxidant combined with it,” she added, noting that this can be dangerous.

Dr. Radford noted that another danger is that many essential oils, such as cinnamon, mint, or rosemary, can leave burns if used on the skin. “If you choose to apply essential oils dermally, only use them when well-diluted with a carrier oil,” she said.

Is It Ever Safe to Ingest Essential Oils?

This is the one method you definitely want to avoid. “Medical professionals rarely advise people to use this method when it comes to essential oils as there is no real research that supports this method,” Dr. Gupta told POPSUGAR.

Dr. Radford cautioned that certain companies claim it’s OK to ingest their oils because of their high purity — but that’s not the real issue. “The warning against ingestion is not about purity,” Dr. Radford explained. “The concern is that essential oils are so potent that they can cause fatigue, headaches, rashes, and even throat swelling and seizures with only a few drops when used this way.”

Is There Anyone Who Should Avoid Essential Oils?

Although topical application and diffusers are generally safe when used with caution, Dr. Gupta noted that certain people should absolutely consult with their doctors before using essential oils. These include those who are pregnant or breastfeeding; children (especially if they’re prepubescent); people on medications like immunomodulators or ones that cause photosensitivity; and anyone with a history of being immunocompromised, high blood pressure, arrhythmias, migraines, and seizures.

And if you have pets, Dr. Gupta said it’s important to consult with a veterinarian because some essential oils can be deadly to animals.