Most of the time your pet will let you know how they’re feeling. But it can be hard to tell when they’re sick. A little puking here, some weird lethargy there, it can be hard to tell the difference between a little under the weather and the start of a serious problem. However if your home contains an essential oil diffuser, it may be the source of your pet's illness. The ASPCA does not recommend the use of essential oils in areas where your pets have access, unless pets are supervised or the use of the oil is approved by your veterinarian. Cats are especially sensitive to essential oils, and effects such as gastrointestinal upset, central nervous system depression and even liver damage could occur if ingested in significant quantities. Inhalation of the oils could lead to aspiration pneumonia. The most common symptoms for cats and dogs exposed to diffused essential oils are drooling, vomiting, coughing, and sneezing. Diffusing oils can be fatal to cats and dogs that have asthma or other respiratory issues. While respiratory issues are concerns, skin exposure is more dangerous than inhalation. Pets can absorb topically applied oils through their skin, or ingest them orally when they groom themselves. While there are some products made for pets, like flea control products that contain essential oils, those are low concentrations that are safe for pets they are designed for. Cats are particularly sensitive to a lot of toxins because they have fewer metabolizing enzymes in their liver compared to dogs, so don’t use a dog product on your cat. You can still have a diffuser in your home, but keep your pet and your running oil diffuser in separate rooms and avoid using the device for long periods of time.