Stem bug spray is not intended to be inhaled, and breathing it in can irritate your airways, but it is unlikely to cause serious harm in the amounts you’d encounter during normal household use. Stem products use plant-based active ingredients like lemongrass oil, geraniol, and similar botanical oils rather than synthetic chemicals. These ingredients fall under the EPA’s “minimum risk” pesticide category, which means the agency considers them low-risk enough to exempt from formal registration. That said, “minimum risk” does not mean “completely harmless to breathe.”
What Happens When You Inhale It
If you spray Stem in an enclosed room and breathe in the mist, the most common reaction is mild irritation of the nose, throat, and airways. You might notice a scratchy throat, slight coughing, or a feeling of tightness in your chest. These symptoms typically pass within minutes to a couple of hours once you move to fresh air.
The botanical oils in Stem, particularly lemongrass oil and its main component citral, are volatile compounds that evaporate quickly. That rapid evaporation is what creates the strong scent you notice right after spraying, and it’s also why the irritation tends to be short-lived. However, people with asthma or other respiratory conditions are more vulnerable. Pesticide exposure, even to botanical formulas, can trigger asthma attacks or worsen existing breathing issues. Some people also develop sensitization over time, meaning repeated exposure leads to stronger allergic reactions including nasal congestion, eye irritation, and breathing difficulty.
Why “Minimum Risk” Has Limits
The EPA exempts certain pesticides from the standard registration process when their active ingredients are considered to pose little to no risk to human health. This category, known as FIFRA Section 25(b), includes common botanical oils like lemongrass, rosemary, and peppermint oil. Stem’s ingredients qualify under this exemption.
What this classification does not include is rigorous inhalation safety testing. The EPA’s exemption is based on the general safety profile of the individual ingredients, not on specific testing of the finished spray product and its effects when inhaled in a closed bathroom or bedroom. So while the ingredients themselves have a long track record of low toxicity, the “minimum risk” label shouldn’t be read as a guarantee that breathing the spray is harmless. It means the EPA considers the risk low enough that it doesn’t require the manufacturer to go through the full pesticide registration process.
Higher Risk for Children and Pets
Children breathe in a greater volume of air relative to their body weight than adults do, which means they absorb proportionally more of any airborne chemical in the same room. They’re also closer to the ground, where heavier spray droplets settle, and more likely to touch treated surfaces and then put their hands near their faces. If you’re spraying Stem in a child’s bedroom or play area, it’s worth taking extra precautions.
Pets face similar concerns. Dogs and cats have smaller body weights and faster breathing rates, and cats in particular are more sensitive to essential oils because their livers process certain plant compounds less efficiently than human or even canine livers do. A brief exposure to the mist from a single application is unlikely to cause a serious problem for most pets, but repeated heavy exposure in poorly ventilated spaces adds up.
How to Use It Safely Indoors
The EPA’s general guidance for spray products is straightforward: do not spray in enclosed areas, and avoid breathing the mist. For a product like Stem, a few practical steps make a real difference.
- Open windows first. Crack a window or turn on a fan before spraying to create airflow. Even one open window in a small room dramatically reduces how much mist lingers in the air.
- Leave the room after spraying. Give the spray 10 to 15 minutes to settle and dry before you, your children, or your pets go back in. The volatile oils evaporate quickly, so most of the airborne irritant will have dissipated by then.
- Spray surfaces, not the air. Direct the nozzle toward baseboards, door frames, and other target areas rather than spraying in wide arcs that create a cloud of mist. Keeping the spray close to surfaces reduces how much becomes airborne.
- Never spray toward your face. If you need to apply a product near your face for any reason, spray it onto your hands first and then apply.
- Keep pets and kids out during application. Let them return once the spray has dried and the smell has faded noticeably.
When Irritation Is a Warning Sign
For most people, a whiff of Stem spray causes nothing more than a brief unpleasant smell. But if you notice persistent coughing, wheezing, chest tightness, or shortness of breath that doesn’t resolve after moving to fresh air, that’s your body signaling a stronger reaction. This is especially relevant if you have asthma, chronic obstructive pulmonary disease, or a known sensitivity to essential oils. Repeated exposure that consistently causes symptoms is worth paying attention to, because sensitization can make each reaction progressively worse.
If you’ve accidentally inhaled a large amount, such as spraying in a small, sealed bathroom with no ventilation, step outside or to a well-ventilated area immediately. Symptoms from a single heavy exposure to botanical oils typically resolve on their own, but prolonged difficulty breathing or chest pain warrants medical attention.